NRLF i THE OCULAR MUSCLES HANSELL and REBER THE OCULAR MUSCLES A PRACTICAL HANDBOOK ON THH MUSCULAR ANOMALIES OF THE EYE BY HOWARD P. HANSELL, A. M., M. D. PROFESSOR OF OPHTHALMOLOGY IN THE JEFFERSON MEDICAL COLLEGE; EMERITUS PROFESSOR OF DISEASES OF THE EYE, PHILADELPHIA POLYCLINIC AND COLLEGE FOR GRADUATES IN medicine; OPHTHALMOLOGIST TO THE PHILADELPHIA GENERAL HOS- PITAL; MEMBER AMERICAN OPHTHALMOLOGICAL SOCIETY; FELLOW COLLEGE OF PHYSICIANS OF PHILADELPHIA, ETC. AND WENDELL REBER, M. D. PROFESSOR OF OPHTHALMOLOGY IN THE MEDICAL DEPARTMENT OF TEMPLE UNIVERSITY; PROFESSOR OF DISEASES OF THE EYE, PHILADELPHIA POLYCLINIC AND COLLEGE FOR GRADUATES IN MEDICINE; OPHTHALMOLOGIST TO THE PHILADELPHIA GENERAL HOSPITAL; CONSULTING OPHTHALMOLOGIST TO THE RUSH HOSPITAL FOR CONSUMPTIVES; MEMBER OXFORD OPHTHALMOLOGICAL CO!^GRESS; PAST PRESIDENT AMERICAN ACADEMY OP OPHTHALMOLOGY AND OTOLARYNGOLOGY. WITH 3 PLATES AND 82 OTHER ILLUSTRATIONS SECOND EDITION, REWRITTEN, ENLARGED PHILADELPHIA P. BLAKISTON'S SON & CO. 1012 WALNUT STREET 1913 ^^' Copyright 1912, by P. Blakiston's Son & Co. Printed by The Maple Press )'ork. Pa, PREFACE Since the authors presented their first edition of a "Handbook on the Muscle Anomahes of the Eye," the interest in this subject has grown with the increasing demands and new problems ha\'e arisen which to-day demand solution and suggestions for their practical relief. As in the previous volume, the subject matter still represents in the main, the essence of the lectures delivered in the regular courses at the Philadelphia Polyclinic. The authors have again sought " to avoid discussions and speculations, to emphasize methods that have stood the test of their own experience, and to omit no important data that have been recognized as trustworthy." H. F. Hansell, Wendell Reber Philadelphia, Pa. 257864 CONTENTS PART I. ANATOMY AND PHYSlOLOCiY. Pack Anatomy 3 Physiology 17 Innervation 17 Nuclear Centers 18 Cortical Centers ig Theory of Innervation ig General Considerations 21 The Law of Direction 22 Corresponding Points 23 Physiologic Diplopia 24 Synergistic Muscles 26 Associated Muscles 28 Antagonistic Muscles 30 The Stcreos(Oi)e 31 Evolution of Binocular Vision 34 Tests for Binocular Vision 37 PART II. STRUCTURAL ANOMALIES. OCUX.A.R Palsies 43 Symptomatology 46 Diagnosis 49 Special Paralyses 52 Prognosis 66 Treatment 67 Spasm of the Ocular Muscles 70 Nystagmus 70 PART III. FUNCTIONAL ANOMALIES. Heteroi'horia 75 General Considerations 75 Concerning Prisms 80 vii Mil CONTENTS. Kflalion Hctvveen Accommodation and Convergence 82 Methods of Diagnosis 88 Musrulo-dynamics 98 Arc Rotations 109 Esophoria 114 Exophoria 126 Hyperphoria 141 Dccentering Lenses 157 Testing Prismatic Lenses 159 IIeterotropia 163 Esotropia 165 Monocular 170 Alternating 180 Exotropia 186 Hypertropia 195 PART IV. OPERATIONS ON THE MUSCLES. Anesthesia 205 Antisepsis, Asepsis and Instruments 206 Tenotomy 207 Advancement or Resection 212 Index: 221 PART I. ANATOMY AND PHYSIOLOGY ANATOMY. The voluntary movements of the eye are under the control of six pairs of muscles, six in each orbit. In any and all movements the eyes are associated in their rotations and all the muscles are engaged, some actively and some passively, contracting and re- laxing thus maintaining the balance or equipoise of the two eyes necessary for binocular single vision. In the study of the functions of the muscles collectively and indi- vidually the orbital fascia must be considered (Fig. i). Posteriorly the muscles are sheathed in delicate transparent connective tissue. Fig. I. — Diagrammatic representation of the relation of the globe to the orbital fascia. (Merkel and Kalius.) When they have almost reached the eye ball the sheaths become thicker and hea\aer. Anteriorly the fascia divides, leaves the muscles and forms a strong fibrous sheath or cufif extending to the orbital wall where it is securely inserted. It sends off branches to support the upper division of the lacrimal gland, to unite the superior rectus with the levator palpebrae and the inferior rectus with the tarsus of the lower lid. On the nasal side the insertion of the fascia is double, the upper part forming the trochlea and 3 ANATOMY AND PHYSIOLOGY. supporting the superior oblique after it leaves the trochlea; the lower is bent backward and forms in the vicinity of the posterior edge of the nasal bone a wide insertion which reaches to the floor of the orbit. The function of the fascia is to limit the efTect of Levator palpfbrao super! Eyebal' Lacrymal gland Inferior obliquc- E.ternal r< Superior oblique iendon Pulley Internal rectus i -Optic I Superior oblique m. Levator patpebrae superioris m- Superior rectus m. ' Fig. 2. — The orbital muscles. (Deaver.) muscle action, to hold the ball firmly in its place in the orbit, and to coordinate or balance associated contraction and relaxation. Of the six muscles in each orbit four are straight and two oblique (Fig. 2). ANATOMY. 5 The external rectus, supplied by the Oth nerve, arises from two heads — the larger from the greater wing of the sphenoid in the external and lower border of the sphenoidal fissure; the smaller from the outer margin of the optic foramen. These two heads soon become united to form the body of the muscle which runs forward and outward, almost in contact with the outer wall for nearly half its length, and loosely bound to it by connective tissue. It is attached anteriorly to the sclera by a tendon 3.7 mm. in length, 9.2 mm. in width in a convex line, the convexity toward the cornea, 7 mm. from the outer limbus. From the tendon of the external rectus, as from those of all the other muscles, adminicula, or side attachments, are given off to the sclera which seem to strengthen the insertions. The area in cross section of its thickest portion equals 16.73 sq- rnm. Its length is 45 mm. (average for adults). The external rectus controls the outer half of the field of fixation and rotates the cornea hori- zontally temporalward. It has no action in tilting the upper end of the vertical meriiand of the cornea either inward or outward. The internal rectus, supplied by the 3d nerve, arises by a tendon common to it and to the inferior rectus from the inner margin of the optic foramen, runs forward, lying close to the inner wall of the orbit and is inserted into the sclera by an almost vertical tendon 8.8 mm. in length and 10.3 mm. in width, at a distance of 6.00 mm. from the inner limbus. The area of its thickest portion is 17.39 sq. mm. and its length is 40.8 mm. It controls the inner half of the field of fixation, rotates the cornea horizontally nasalward, and has no torsional action. The superior rectus, supplied by the 3d nerve, arises by a tendon common to it and to the inferior and internal rectus at the upper margin of the optic foramen. In its course forward it perforates the orbital fat lying just under and lightly connected with the levator palpebrae, curves round the ball, pierces the layer of orbital fat and passes obliquely to its insertion into the sclera anterior to the equator and 8 mm. posterior to the corneo- scleral border, bv a tendon 5.8 mm. in length and 10.6 mm. in 6 ANATOMY AND PHYSIOLOGY. width. Its largest area is ii 1/3 sq. mm. and its length 41.8 mm. From these figures it will be seen that the superior rectus is the weakest of the straight muscles. It controls the upper half of the field of fixation, turning the eye up, this vertical movement increasing as the eye is abducted and diminishing as the eye is adducted; it also rotates the cornea horizontally nasal ward and tilts the upper end of the cornea in, more in adduction, less in abduction. The inferior rectus, supplied by the 3d nerve, has the same origin as the internal. It lies close to the floor of the orbit and is attached to the sclera by a tendon 5.5 mm. long and 9.8 mm. wide, at a distance of 7.2 mm. from the limbus. It is indirectly, by means of the lower orbital fascia, connected with the tarsus of the lower lid. Its largest area in section is 15.85 sq. mm. and its length is 40 mm. It controls the lower half of the field of fixation turning the eye down, the vertical movement increasing with abduction, diminishing with adduction. It also turns the eye laterally in and rotates the upper end of the vertical meridian of the cornea out, these effects increasing as the eye is adducted, decreasing as it is abducted. The superior oblique, a long fusiform muscle supplied by the 4th nerve, has its origin a little above the common origin of the recti from the lesser wing of the sphenoid, passing forward and upward to the inner angle of the orbit, where as a tendon it plays in, and is supported by, a fibro-cartilaginous ring in the fossa trochlearis. Upon resuming its course (the direction of which is now backward, downward and outward at an angle of 53° with the optic axis), it passes beneath the superior rectus, to be at- tached posteriorly to the sclera midway between the cornea and the optic nerve foramen 16 mm. from the limbus. The inser- tion forms nearly an antero-posterior line, the large part of the tendon being attached posterior to the vertical equator of the globe. The length of the tendon, which commences before the ring is reached and is continued to the scleral end, is 19.5 mm., and the width of the insertion varies from 6.8 mm. to 14 mm. It moves the eye down and out (temporalward) and rotates the ANATOMY. 7 upper end of the vertical meridian inward, both movements increasing in abduction, diminishing in adduction. The inferior oblique, supplied by the 3d nerve, arises from the anterior portion of the middle of the floor of the orbit in a depression in the superior maxillary bone j-ust external to the an- terior end of the lacrimal groove and posterior to the margin of the orbit. As a thin narrow muscle, it passes outward, backward and upward, beneath the inferior rectus, and is inserted by a horizontal attachment, about 10 mm. in width, into the sclera between the inferior and external recti on the posterior hemisphere of the ball, 17.3 mm. from the limbus. It controls the upper outer half of the field of fixation, turning the eye upward, and temporalward, which effect increases in adduction, and diminishes in abduction;^ it also turns the eye (laterally) outward, more in abduction, less in adduction. To Summarize. — The insertion of the internal, inferior, external and superior recti lie, in round numbers, 5, 6, 7, and 8 mm. respectively from the corneal margin, forming what is known as the spiral of insertions (see Fig. 3). Naturally, the internal rectus has therefore the greatest mechanica' advantage and the inferior rectus the next. ► The levator palpebrse, while not strictly one of the extrinsic muscles of the ball, is closely allied, anatomically and pathologic- ally, to them and should be included in a description of the mus- cles of the orbit. It arises from the under surface of the lesser wing of the sphenoid above the optic foramen, passes forward above and in close juxtaposition to the superior rectus in the first half of its course, and is inserted into the upper edge of the tarsal cartilage by an aponeurosis as broad as the cartilage. These two ' Volkman's results of measurement of movements, quoted by Weiland, Archives of Ophthal., January, 1898, are: Rect. Ext. moves eyeball out, up; rotates upper cornea inward. Rect. Int. moves eyeball in, up; rotates upper cornea outward. Rect. Sup. moves eyeball up, in; rotates upper cornea inward. Rect. Inf. moves eyeball down, in; rotates upper cornea outward. Obi. Sup. moves eyeball down, out; rotates upper cornea inward. Obi. Inf. moves eyeball up, in; rotates upper cornea outward. 8 ANATOMY AND PHYSIOLOGY. muscles are so intimately associated in their location and course- that contraction of one involves partial contraction at least of the other. Capsule of Tenon. — The fascias of the muscles are not so distinctly separated from each other that they may be individu- ally described, for they are closely interwoven with themselves and with the connective tissue leaves which bind together the orbital fat. The ball itself is surrounded by a thin, relatively strong con- nective tissue capsule (Tenon's) lined with endothelium which is SUP. RECTUS. ' 8mm. 6 m ni ■ / A/ f. RECTUS. Fig. 3. — The spiral of insertions. developed out of the sheets in the fat behind the orbit and is di- rectly connected with them. It is connected every where with the ball by tender connective tissue bundles. It takes the place of the bony walls in the movement of the eyeball as in a ball and socket joint. Instead of the synovial space found in joints, the capsule of Tenon is here pierced by connective tissue bundles. It is said by Schwalbe to be a lymph space — (Tenon's space) — which is denied, however, by Langer, who says it never contains lymph nor is it connected with the lymph spaces of the eye. The "adminicula" (side attachments) of the muscles already described ANATOMY. 9 are to be considered as collections of these connective-tissue bundles. Through a small opening in the capsule, the latter may be blown up easily. Tt ends a short distance behind the cornea, having amalgamated with the conjunctiva. Posteriorly it ends in an irregular line surrounding the ciliary nerves and blood-vessels and forming a ring, i cm. in diameter through which the optic nerve passes. There are two layers to the capsule — one lying very close to the eyeball, the other surrounding it more or less loosely. The muscular tendons break through the capsule in slits and are connected with its edges by connective tissue. The muscles are covered by delicate connective tissue about one-half way to the ball, then the sheath becomes heavier. This heavy fascia does not accompany the tendons through their slits in Tenon's Capsule, but bends away inward and outward. On that side toward the ball it amalgamates with the capsule and strengthens the above described strong connective-tissue ring. The outer half of the fascia becomes much thicker and gives off branches and sheaths which bend sideways and attach themselves firmly to the bone. There are three such insertions. On the up- per temporal aspect the fascia from three muscles collects. The insertion is so placed that it supports the upper lacrimal gland. From it are given off the connective-tissue sheaths of the levator palpebrse and the superior rectus and the (from below) external rectus. On the nasal side the insertion is double, upper and lower, the upper to the superior oblique; the lower is bent back and forms in the vicinity of the posterior edge of the nasal bone a wide, downward inclining line which begins at the inner canthus and reaches to the floor of the orbit. Differences of opinion prevail as to the function of Tenon's capsule. It was long believed and still is held by many authorities that the two layers of the capsule enclose a lymph space connected by lymph vessels with the suprachoroidal space, and thus form an important link in the chain of lymph spaces w^hich connect the eye with the intracranial lymph system. Leber (Graefe Saemisch) on the other hand, asserts that it is not a lymph space, nor is it connected with the lymph spaces of the eye. Its function is lO ANATOMY AND PHYSIOLOGY. somewhat like that of a synovial membrane and permits the ocu- lar movements without friction. Check Ligaments. — In operations on the muscles, the prolonga- tions of the enveloping sheaths of fascia must not be disregarded. Difficulty in picking up the tendons with the strabismus hook is often encountered, because the incision has failed to divide both layers of the capsule, and the effect desired of a tenotomy is not secured, because attention has not been given to the radical supporting attachments derived from the capsule and the check ligaments which are a portion of the orbital fascias. Serious in- FiG. 4. — The internal check hgament (a) serves to prevent excessive ac- tion of the external rectus after extensive tenotomy of the internus. Fig. 5. — The internal check hgament (a) being put upon the stretch by the contracted internal rectus. Fig. 6. — ^Diagram of the check Ugaments. a, internal check hgament; b, external check Hga- ment. fiammation (tenonitis), with extension of the inflammatory pro- cess backward, may result from traumatism to this serous envelope (Fig. 4). These condensations of connective tissue which are more or less gathered together opposite the four recti muscles and are known as the check ligaments are not necessarily as sharply limited as they are shown in Fig. 4 and yet they bear a distinct relation to the neighboring muscles and they are therefore today recognized under the above name. Ordinarily no force is exerted by them, but when for instance the interni are under forced action as shown in Fig. 5 the internal check ligaments serve to prevent exaggerated action on the part of the interni muscles while the external check ligaments are relaxed. Moreover, after extensive tenotomy of ANATOMY. II the internal rectus, the corresponding check ligament is put upon more or less constant stretch and may e\'en limit the action of the eyeball somewhat (Fig. 6). Ofb:;i I fascu Capule of Tenon ( fM Sufx-rioj r»ttus m'. LayMor palpebrji 1 9up«rioris m. [ Coinection b..;wcen superior rcclu; m. and levator pjlpcbro) tup«rioii( m Capsule of Tenon Fornix conjunctiva Suptuip Orbitil.^ I orblto-tarsal lii Supravaginal lymph rp • . Fikfous shelih u( uic n Iniervaginal lymph sp ; Pe'iosieum of orbit i Optic n. \ Capsule of Tenon Check lig of inferior rectus m. inferior .oblique m OrbiUl fascia Capsunof Tenon Fig. 7. — Tenon's capsule and orbilal fascias. (Deaver.) The space between the ball and the orbital walls, not occupied by muscles and nerves, is filled with fat in great part, and by con- 12 ANATOMY AND PHYSIOLOGY. nectivc tissue. The connective tissue of the orbit is so arranged as to form light fibrous bands, probably containing elastic tissue, supporting and steadying the muscles during action and maintain- ing the suspension of the ball (Fig. 7). The functions of the fascia are limitation of muscle effect; to hold the eyeball firmly in its position, to guard the conjunctiva in movements of the globe and to associate the action of the su- perior rectus and the upper lid, and the inferior rectus and the lower lid. NERVE SUPPLY OF THE INDIVIDUAL MUSCLES. The 3d. 4th, and 6th cranial nerves, known as the oculomotor, pathetic and abducens nerves, together supply the external ocular P"lG. 8. — Nerves of the orbit. (Dearer.) muscles (Fig. 8). The 3d nerve also gives off a branch to the oph- thalmic or lenticular ganglion, forming its motor root to the inte- rior ocular muscles. The scheme or hypothesis which explains the ANATOMY. 13 largest number of 3d ner\e nuclear problems is, probably, that of Bernheimer' (Fig. 9). The vascular supply is shown in Fig. 10. As the libers of the third nerve leave the mass of gray substance which lays along each side of the median line, in the anterior part of the fourth ventricle, they converge as they pass downward to pierce the dura mater below the posterior clinoid process; the nerve-trunk there passes along the outer wall of the cavern- Fic;. Q. — Schematic projection of the nucleus of the third and fourth nerves in the floor of the fourth ventricle, a and b, nucleoli for the intraocular muscles (iris and ciliary muscle) ; c, levator nucleolus; d, superior rectus nucleolus; e, internal rectus nucleolus; /, inferior oblique nucleolus; g, inferior rectus nucleolus; h, fourth nerve nucleus or superior oblique nucleus. (Bernheimer, Graefe-Saemisch Handbuch, second edition.) ous sinus, enters the orbit through the sphenoid fissure and divides into two branches. The superior division supplies the superior rectus and levator palpebrae; the inferior division separates into three branches, one going to the internal rectus; and the third, and largest, to the inferior oblique; and one to the inferior rectus. A fourth goes to the short root of the lenticular ganglion. From the lenticular ganglion are given off the long ciliary ner\es which ' Some authorities prefer Perlia's; others Kahler & Pick. 14 ANATOMY AND PHYSIOLOGY. perforate the sclera around the optic nerve, pass forward between the sclera and choroid and are distributed to the iris and ciliary muscle. The terminal branches anastomose finally with the terminals of the seventh. The nerve-trunk also receives fila- ments from the cavernous plexus of the sympathetic, and its superior division is not infrequently connected with the ganglionic branch of the nasal nerve. Fig. io. — Vascular supply to the oculomotor nuclei, a, Roof of the corpora quadrigemina; b, acqueduct of Sylvius; c, sphincter-iridis and ciliary muscle nucleus; d, f, and g, vascular supply to the remaining nuclei. (Bernheimer, Graefe- Saemisch Handbuch, second edition.) The 4th, pathetic or trochlear nerve supplies the superior oblique muscle. Its deep origin can be traced to the nucleus which lies beneath the aqueduct of Sylvius, behind and on a lower level than the third nerve nucleus. The fibers pass as they emerge to the dorsal aspect of the aqueduct and decussate with the fibers of the opposite side ?) . The nerve-trunk pierces the dura mater near the posterior clinoid process, passes with the 3d nerve along the outer wall of the cavernous sinus and enters ANATOMY. 15 the orbit through the sphenoidal fissure, being the highest of the nerves passing through the orbit. It also receives filaments from the cavernous plexus of the sympathetic, and transmits a twig to the lacrimal. The nucleus of the 6th or abducens nerve consists of multiple ganglion cells lying immediately under the center of the floor of the 4th ventricle on either side of the median sulcus. It is bor- dered on its inferior, inner and upper sides by the first, second and third portions of the facial nerve. The fibers run obliquely downward to emerge at the lower border of the pons. The connections of the 6th nerve nucleus are said by Bruce {loc. cit.) to be as follows: with the second part of the root of the facial nerve and the segment of the 3d nerve nucleus supplying the internal rectus; with the auditory nucleus and with the cortex of the opposite cerebral hemisphere, and perhaps with that of the same side. The nerve penetrates the dura mater on the basilar surface of the sphenoid bone, passes through the posterior or clinoid processes, enters the cavernous sinus, and finally the orbit through the sphenoidal fissure, to be distributed to the external rectus muscle from its inner surface. It also receives filaments from the carotid and cavernous plexus of the sympathetic nerve, from Meckel's ganglion and from the ophthalmic nerve. VASCULAR SUPPLY. The vascular supply to the muscles is derived from the muscular branches of the ophthalmic artery, one of the terminal branches of the internal carotid. The ophthalmic artery at its origin is 2 mm. in diameter. It passes through the optic foramen under the optic nerve, supplying its sheaths and perineurium, later perforating and supplying the nerve-substance itself. Soon after its entrance into the orbit, it gives oft' the muscular branches. All the blood-vessels of the orbit are characterized by their tortuous course and their lax attachments to flexible structures. They are thus enabled to accompany the movements of the ball without tearing. The muscular arteries are two in number, the smaller passing l6 ' ANATOMY AND PHYSIOLOGY. up and medianward, the larger downward and laterally, supply- ing the muscles in their course. They give off the anterior ciliary branches which perforate the tendons of the muscles and the sclera, and supply the ciliary region and iris with blood. (Section of one of these arteries in tenotomy often gives rise to profuse, but never alarming hemorrhage.) The arteries are accompanied by veins situated similarly and described under similar names. The most important orbital vein is the superior ophthalmic, with which all venous branches in the orbit are in direct or in- direct connection. It collects blood from the frontal, nasal, supra-orbital, angular, venae vorticosse, and the central retinal veins. Its course is along the superior rectus, backward in the muscular cone, emptying into the cavernous sinus. PHYSIOLOGY. INNERVATION. The muscles governing the movements of the eyeball, the ac- commodation and the iris are innervated by the 3d, 4th and 6th pair of cranial nerves and the carotid plexus of the sympathetic system. The former have their deep origin in the posterior ex- tremity of the aqueduct of Sylvius and the anterior part of the floor of the 4th ventricle. The muscular movements are volun- tary because they are represented by distinct areas in the cor- tex. From these cortical centers are derived nerve fibers which run indirectly to the nuclei and undoubtedly have con- nections with other centers in the brain, the functions of which are associated. The fibers have not been dissected or strictly outlined. Their presence must be assumed in the explanation of mental processes, part of the evidence of which are the voluntary, although not always conscious, ocular movements. The nuclei on the other hand have been studied, their exact location, their relations to each other and their functions to a large extent determined. From the nuclei large numbers of nerve fibers are given off which immediately unite to become distinct nerve trunks easily seen at the base of the brain and followed to their exit through the sphenoidal fissure to be distributed to their respective terminations in the muscular tissues and probably anastomosing with the terminal branches of the 7th nerve. Russell's experiments have led him to conclude that the cere- bellar cortex plays no little part in ocular movements and that it is associated with the cerebrum in these functions. The ac- companying drawing, Fig. 11, based on Russell's experiments, indicate the areas which are supposed to preside over the different eye movements. It will be observed that they are above the center of the fissure of Syhius just anterior to the large motor 2 17 15 ANATOMY AND PHYSIOLOGY. area, and, moreover, that they are close to the facial area, and on the left side. NUCLEAR CENTERS. The mass of cells composing the nucleus of the 3d lies on both sides of the median line next to the corpora quadrigemina and under the aqueduct of Syhius anterior to and on the floor of the 4th ventricle. The nucleus is from 6 to 10 mm. in length and of varying breadth mingling imperceptibly with adjacent cells. Posteriorly they encroach upon the cells of the 4th Fig. II. — The external surface of the right half of the brain of the ape (Macacus Sinicus). (After Russell, Journal of Physiology, vol. 17, p. 8.) i, Upward move- ment of both eyes; 2, downward movement of both eyes; 3, movement of both eyes upward and to the opposite side; 4, movement of both eyes downward and to the opposite side; 5, convergence. The numbers denote the chief foci, excitation of which evoked movements of the eyes other than conjugate turning to the opposite side from the hemisphere stimulated. nucleus w^ithout a distinct line of demarkation between them. The mass may be divided into nucleoli each with its separate function and muscle control. In the accompanying diagram the anatomy and physiology is schematically shown. It will be noticed that from some of the nuclei the fibers run direct to the muscles on the same side, while others are crossed to stimulate those on the other side, the crossing taking place mostly in the anterior half of the nucleus. Speaking generally the inner or median part of the nucleus belongs to the intraocular muscles and the outer portions to the extra-ocular muscles. The PHYSIOLOGY. 19 anterior and ])rinci])al part of the nuclear masses belongs to the 3d nerve. Adjoining the proximal or posterior end of the posterior corpora quadrigemina on both sides are the nuclei, right and left, of the trochlearis. Much farther back and in juxtaposition with the facial muscles and fibers is the nucleus of the abducens. CORTICAL CENTERS. Having conducted a large number of experiments on monkeys to determine the site of the centers for eye movements, St. Bern- heimer (Graefe Saemisch, second edition) has reached the follow- ing conclusions : i. The gyrus angularis and especially its middle part of both hemispheres is the only cortical center for synergic eye movements. 2. The right gyrus angularis controls move- ments toward the left, up and left, and down, the left gyrus controls movements toward the right, up and right, and down. 3. The anterior corpora quadrigemina are neither a reflex center for eye movements nor the passage for the neurons. 4. Since after median section of the brain between the aqueduct of Syhius and the nuclei region of the eye muscles irritation of both angular gyri produces no eye movement, therefore the connection-neurons between the nuclei and the cortex are all crossed in the angular gyrus in the median line under the plane of the aqueduct of Sylvius between it and the nuclei. 5. The end filaments of the con- necting fibers communicate probably by other cells (schalzellcn) with the roots of the motor ganglion cells of the nuclei. 6. The schalzellen lie probably imbedded and scattered in the central gray matter and form no cell mass. 7. In consequence of partial crossing of the 3d, the total crossing of the 4th, and the con- nection of all the oculomotor nuclei with each other, it may well be asked whether the crossing connecting fibers of one angu- lar gyrus equally influence the muscles of both eyes ? THEORY OF INNERVATION. To outline the structure and function of each of the individual eye-muscles is a relatively simple matter, yet it is by no means so 20 ANATOMY AND PHYSIOLOGY. easy a task to give a satisfactory explanation of the innervational state of the eye-muscles corresponding to all the positions the eyes may assume in monocular or binocular fixation. The theory that has gained the widest acceptance is the so-called innervational theory, so ably championed by Hansen Grut, 1898. It ])rovides that every contraction of a muscle or set of muscles to produce oc- ular movement in a given direction is accompanied by relaxation of the muscle or set of muscles that are directly antagonistic to the contracting muscles, which relaxation keeps even pace with the contraction going on in the muscles producing the deviation. As the eyes are capable of being easily rotated there must, in order that single vision be preserved, be a balance among the forces that tend to move the eyes in various directions. This balance is possible only under two conditions: i, that all the muscles be slack and exert no tension (an untenable hypothesis) ; or 2, that all the muscles so tend to contract as to cause an equal rotational strain in all directions. Hence, we suppose that the muscles are always in a state of partial tonic contraction, at any rate during the period of full consciousness. There is no limitation to the directions in which the eye can be rotated by the action of one or more muscles, and under certain circumstances a contraction of all the muscles produces a slight enophthalmus. The primary position of the eyes is observed when an individual holds the head erect and gazes straight in front toward infinity in the horizontal plane of the eyes. The predominately active muscles in the following movements from the primary position are: Right and left turning; only the rectus externus and rectus inlernus. Upward turning; rectus superior and inferior oblique. Downward turning ; rectus inferior and superior oblique. Up and out turning; rectus superior, inferior oblique, and rectus externus. Down and out turning; rectus externus, rectus inferior and superior oblique. Down and in turning; rectus internus, rectus inferior, and superior oblique. Up and in turning; rectus internus, rectus superior and superior oblique. These are the eight principal secondary positions, and in all the degrees of the circle between them the rotation will be accom- PHYSIOLOGY. 21 plishcd by the combined action of the muscles normally turning the cornea to these positions. The extent of the turnings in the field of fixation varies, according to different observers. The average is probably as follows : up up-out up-in out in down down-out down-in 40-50 35-50 40-55 35-55 40-4S 40-70 35-60 25-60 (Diiane). The discrepancies arise from variations in the normal power of the muscles of one individual as compared with another, and the degree of attention and effort of which an individual is capable. Also, in determining the rotation by Stevens's tropometer, the form of the ball must be taken into consideration. Such wide variations, as the averages given above, are confusing to one who endeavors to determine whether a certain movement is normal or otherwise. GENERAL PHYSIOLOGIC CONSIDERATIONS. The Law of Projection.— To properly understand the phe- nomena of \ision, certain peculiar functions of the retina, optic nerve, and associated brain apparatus must be clearly appre- hended, for they lie at the very basis of these phenomena. While it is true that images are formed on the retina, we do not actually see the retinal images. In fact, we do not actually see anything in the eye but something outside in space. The retinal image is conveyed by way of the optic nerves and tracts to the brain, there to determine certain changes. These changes or ejects the brain then refers or projects outward in a definite direc- tion into space as an external image or facsimile of the object which produces it. So that what we see as external images are really projections outward of retinal images. This law of outward projection is important. It is not a new law, specially made for the sense of sight, but only a modification of a general law of sensation. This general law is that irritation or stimulation in any portion of a sensory fiber is referred to its peripheral ex- tremity. If the ulnar nerve is pinched in the hollow on the inner side of the point of the elbow, pain is felt in the little and ring 22 ANATOMY AND PHYSIOLOGY. fingers, where this nerve is distributed. In the case of the optic nerve the impression is so wholly projected outward that we arc unconscious of any sensation in the eye at all. Hence what we are accustomed to call the field of view is nothing else than the external projection into space of various retinal stimulations. The Law of Direction. — The direction of external projection may be exactly (or nearly exactly) defined as follows: The central ray of each point in the field of view passes straight through the nodal point of the lens without de\dation to the retina. It is evident then that every retinal rod and cone has its inevitable related point or spot in the field of view (visual field) and vice versa. The two points — retinal and spatial — exchange with one another by impression and outward projection along the straight lines connecting them. This is represented in Fig. 12 in which S S represents the spatial concave and R R the retinal expanse, with straight lines of rays of light connecting. A ray from a point c in space passes in a straight line through the nodal point of the lens w, and strikes a certain retinal rod c; that impression is projected by the rod (or referred by the brain) back along the ray line to the place whence it came. Study of the figure shows that the position of all retinal images must be the reverse of the objects in space — that the upper part of the field of view corre- sponds to the lower part of the retina and the lower part of the field of view (visual field) to the upper part of the retina. Similarly the right and left sides of the visual field are related to the left and right sides respectively of the retina. These two laws — the law of external projection and the law of direction — are two of the most fundamental laws of vision. Fig. 12. — Scheme of the law of direction. The larger circle repre- sents the limits of space; the smaller one the retina. PHYSIOLOGY. 23 The first shows why objects are seen externally in space; the second gives the exact place where they are seen, that is to say where the brain locates them. The general law of projection is not followed \ery exactly with respect to the very forwardmost portions of the retina in the region of the ora serrata. What has been thus far said treats only of the phenomena of monocular \ision. But most individuals possess two eyes, and these are not to be considered as mere duplicates so that if we lose one we still have another. Quite on the contrary, the two eyes ordinarily act together as one instrument. There are many visual phenomena and many judgments based upon these phe- nomena which result entirely from the use of two eyes as one in- strument. The phenomena of binocular vision are far less purely physical than those of monocular vision. They are also more obscure, illusory and difficult of analysis because more subjective and more closely allied to psychical phenomena. Corresponding or Identical Points. As is well known, the retinas are two deeply cup-shaped ex- pansions of the optic nerve. R and L (Fig. 13) represent a fiat (or Mercator) projection of these two cups. The black spots in Fig. 13. — Mercator projection of the two retinas; showing corresponding retinal points. the centers represent the central spots. If now we draw vertical lines (vertical meridians) A, B,A', B', through the central spots and divide the retinas into equal halves, then the left or shaded halves would correspond point for point; i.e., the internal or nasal 24 ANATOMY AND PHYSIOLOGY. half of one retina corresponds with the external or temporal half of the other and vice versa. More accurately if the concave retinas be divided by coordinates like the lines of latitude and longitude of a globe (ab, and xy being the meridian and equator), then points of similar longitude and latitude in the two retinas, as D,D', and E,E/ are corresponding points. Of course the cen- tral spots will be corresponding points; also points on the vertical meridians, A,A', B,B', at equsd distances from the central spots will also correspond. ^ These phenomena therefore afford the basis for the following: Law of Corresponding or Identical Retinal Points. — Ob- jects are seen single when their retinal images Jail on corresponding or identical retinal points. Of course it is true that as there are two retinas there are natu- rally two retinal images of every external object, and since, as has been shown, retinal images are projected outward into space as external images, one will certainly have two external images of every object. If then there are two external images for every object, it may be asked why are not all objects seen double? And it may be answered that all objects are indeed seen double except under certain conditiois. PHYSIOLOGIC DIPLOPIA. The phenomena of double images of all objects except under certain conditions is a fundamental one in binocular vision, yet it is commonly overlooked by even the most intelligent persons unaccustomed to analyzing their visual impressions. If one holds up one's index finger at arm's length and then looks not at the finger, but at the wall or the ceiling or the sky or any suffi- ciently removed expanse, two images of the finger will be seen, the left one belonging to the right eye and the right one to the left eye. This is easily proven by shutting first one eye and then the ^ In some eyes the apparent vertical meridian which divides the retinas into corresponding halves is not perfectly vertical, but slightly inclined outward at the top. This would effect all the meridians slightly, but the effect is insignificant. PHYSIOLOGY. 25 Other and observing which image disappears/ To confirm this phenomenon another experiment may be tried. With the two forefingers placed directly in front of one, in the median plane of the head one at arms length, the other one half that distance (see Fig. 14) it will be observed that if the farther finger is seen single, the nearer one is seen double; if the nearer finger is ob- FiG. 14. — Experiment to illustrate physiologic diplopia. If the far finger is looked at the near finger is seen double (crossed diplopia); if the near finger is looked at, the far finger is seen double (uncrossed diplopia). served this one will be seen single, but the farther one double; when the farther one is seen double, the right image disappears when the right eye is closed; that is to say the images are un- crossed or homonymous. When the nearer one is seen double, the right image disappears when the left eye is closed; that is to say the images are crossed or heteronymous. The important fact to be borne in mind is that it is impossible for both fingers to be seen as single objects at the same time. Therefore it is evident that when we look directly at anything we see it single, but that all ' Some persons find difficulty in consciously recognizing the two images. It is not uncommon for such persons to habitually neglect one image until it finally drops out of consciousness. Hence they are likely to become either right or left eyed. 26 ANATOMY AND PHYSIOLOGY. things situated at that same instant either nearer or farther away than the object looked at are seen double whether consciously recognized as double or not. Fortunately, in ordinary every day use of the eyes this physiologic diplopia is disregarded because of the overwhelming dominance of the fusion sense and single vision results. ON SYNERGISTIC MUSCLES, OR THOSE WHICH ASSIST EACH OTHER. It has been shown in the chapter on anatomy and physiology that the external rectus and the internal rectus have purely lateral action; but that the superior rectus moves the eyeball not only upward, but also inward (medianward) while the inferior rectus draws the eyeball downward and also inward (median- ward). Also, that the superior oblique muscle moves the cornea SIP RCCTOS /^vrOBl/QVl Up ana /n - v / Vpa/idOut' Op and left. \ / UpondRifkL Ltr I yK n/Crn/ l/vr RECTUS SOP.OBLIQUE Down and /n = Down, ond Out-. Duwnitnd Left. J) uun and Right. Fig. 15. — Showing the dominant action of the muscles of^the right ej-e. This diagram is based on the presumption that the eyes are in the priman' position when the movement in the various directions begins. downward and outward (temporal ward) and the inferior oblique moves the eyeball upward and outward (temporalward) . These movements may be represented diagramatically as in Fig. 15. As a matter of convenience and memory help the student will do well to remember that the right inferior oblique for instance moves the right eyeball up and right rather than up and out or temporal- ward. The same is true of all other motions imparted by the muscles to the globe. PHYSIOLOGY. 27 Further study of Fig. 15 (which refers to the right eye) will show that both the superior rectus and the inferior oblique of the right eye are elevators of that eye and that when they act together they rotate the eyeball directly upward, their torsional actions in opposite directions neutralizing each other. These two muscles are therefore said to be synergistic muscles. Similarly the superior oblique and the inferior rectus of the right eye are both depressors of the right globe (their torsional effect being neutralized) and they also are synergistic muscles.^ //vr. oouQU£ svp. fiecTus Up and Ouf = \ / l^P and/n - Vp UKd left. \ / iiptr/xl/llffAl LEFT ^2^:^^::^ xz /^yrnecrus ^^^^^^ SUP. OBUQt/£ /\f. /iccms Down and Out. Douin o.?ui /n- Domn and left. Down and Higfit. Fig. 16. — Dominant action of the individual muscles of the left eye. In considering Fig. 16 which refers to the left eye, it will be found that exactly the same state of affairs obtains so far as the left eye is individually concerned, only it will be seen at a glance that while the right superior rectus moves the right globe up and left, the left superior rectus moves the left globe up and right. The same difference obtains with the inferior rectus of the two eyes and with both obliques, and these differences must be closely observed as they lead directly to the study of the eyes as a pair. ' It can also be easily seen that in moving the right eyeball directly to the right the external rectu predominates in that movement but the superior and inferior obUque by joint cont'iction assist in that movement; also that in the movement of the right eyeball to the left, the internal rectus dominates the action but is assisted by the joint contraction of the superior and inferior rectus. This syner- gism obtains in every eye movement that is made and there is no movement of the eyeballs in which but one muscle is the sok and only muscle concerned. 28 ANATOMY AND PHYSIOLOGY. ASSOCIATED MUSCLES. If Figs. 15 and 16 are now studied side by side it will be seen at once that in the movement of both eyes directly to the right, the muscles that predominate in this action are the right external rectus and the left internal rectus. In movements to the direct left, the right internal rectus and the left external rectus dominate the movement. In movement of the eyes up and to the right the two muscles principally concerned are the right inferior oblique ijfana l£fj- LP a>"i/^/(l/ir fi.suR REC'ras \ / l. sop. rectus BOTH \ / Born EYTS l£xrP,£CTi'S \^ /^TXT/fCCTOS £y£s L£FT H l.\LTI£CTVS /\ L /VTfiECTOS RIGHT i.sop.oei/iii/T / \ n.sop.oBLiQvE ff. TVr. PECTUS / \ / . /, J E. RECTUS DOWN «"r PART III. FUNCTIONAL ANOMALIES HETEROPHORIA. HETEROTROPIA. HETEROPHORIA, GENERAL CONSIDERATIONS. In the study of the relation of the muscles to each other in states of abnormal tension and relaxation (but without paralysis) , we leave the clearly defined field of recognized symptoms and conditions, and enter that of uncertainty, vagueness, and specula- tion; we pass from the logical results of anatomic changes to the confused manifestations of unknown psychologic disturbances. We do not deal with demonstrable lesions of the muscular or nervous system, but with tendencies to inco()rdination, the result of innervational peculiarities that thus far have been untraceable by the dissector's knife or physiologist's microscope. We are brought face to face with the ocular complications of disordered health, of inherited or acquired abnormal susceptibility, of illogical and uncommon results of common causes, of individual idiosyncrasies — in a word, of unbalanced nerve-action. While it is not disputed that functional muscular anomalies follow known causes accprding to known principles of cause and effect, it is maintained that some of the most difficult problems offered for solution cannot be explained by any satisfactory theory. Obstacles surround the examination and treatment of every case and can only be overcome by repeated trials with modern diagnostic methods and the persistent applications of physiologic and conservative remedies. The individual element must not be lost sight of, and every factor, ocular and extraocular, that can have a bearing on the solution thoroughly investigated. The oculist is not the refractor or the tenotomist alone, but is the physician as well. Functional deviations are so intimately bound up with the re- fractive status as to compel frequent mention of the latter in discussing the various forms of muscular imbalance. Indeed, 75 76 . FUNCTIONAL ANOMALIES. no problem in hcterophoria is free from the complicating influence of the action of the ciliary muscle, whether the eye be emmetropic or not. The importance of this relation is so great that some authorities maintain today that all muscular "imbalance" pro- ceeds from errors of refraction, and that the persistent wear of correcting lenses will ultimately dissipate the hcterophoria. Functional deviations of the eye depend, further, for their solution upon heredity, age, sex, social condition, temperament, physique, vocation, hours of work, mental worry, and numerous other minor factors. It will thus be readily seen that they are not so simple in their causes and treatment as has been suggested by some authors. Many of the older writers looked upon such deviations of the ocular muscles as symptoms of a lowering of the general nervous tone (whims of the nervous system, as some have called them), or of some general pathologic process; and although later methods and up-to-date instruments of precision have plainly shown that a goodly number of heterophorias are not symptomatic, but are substantive conditions attended by a train of their own symptoms, the view of these older writers was not without foundation, and it deserves particular emphasis in this day of exceeding specialism. Muscular Balance. — The eyes may be said to be swung and held taut in the orbit by a delicate muscular harness and the orbital fascia. The four recti muscles in combination tend to draw the globe backward into the orbit, which action is opposed in greater or less degree by the tendency of the superior and infe- rior oblique to bring the globe forward. Hence, a slight degree of contraction of all the muscles is necessary to maintain the globe in the proper position during all waking hours. This process, simultaneously active in both orbits, produces coordination of the visual axes, so that when the eyes are directed toward an object, their axes will meet exactly in that object, and the eyes are said to be balanced, or in equilibrium. It is important to remember in this connection that the direction of the visual axes when the eyes are in the anatomical position of rest (resulting from the form of the orbit, the insertion of the HETEROPHORLA.. / / optic nerve and the natural length of the muscles when not inner- vated), is generally divergent, rarely parallel, and hardly ever convergent. But the function of normal eyes never allows in- dependent deviation, hence the parallel direction demanded for distance can never be abandoned while we are awake, and the unconscious innervational habit pulls the eyes from the anatom- ical position of rest to parallelism, which is the functional posi- tion of rest; functional, because the function of the eyes has produced it, and position of rest, because the position assumed by habit and unconscious innervation is free from all exertion. Any disturbance of the factors just mentioned will cause muscu- lar imbalance, and yet want of muscular balance is not incom- patible with perfect binocular vision, for, in many cases, visual axes that tend to deviate are brought back to parallelism by increased innervation to a given muscle or group of muscles, and it is this necessary extra outlay of nervous energy that frequently brings on asthenopia in small degrees of muscular imbalance. Functional disorders of coordination are manifest or latent. There may be an actual turning of one optic axis from the other, involving a loss of associated movement, or the want of coordina- tion may show itself as nothing more than a tendency to deviation. Between these two extremes of want of equilibrium (the one re- presenting the accomplished strabismus, the other latent overac- tion or underaction of synergist muscles) is a middle stage, characterized by the development of either the deviation tendency or the squint, according to the demand made on the different muscles; for example, the insufficiency of the internal recti for near work, described by v. Graefe forty years ago. The study of this subject will be simplified if the student will bear in mind that functional want of equilibrium concerns in all cases the destruction of the normal relation between two sets of opposing muscles rather than the insufficient or overaction of any one muscle. Thus, in esophoria we are dealing with the power of convergence, and not the strength of the internal recti. It is unscientific to attempt to separate the muscular from the innervational apparatus, the more so as the latter comprises both the fusion-force and 78 FUNCTIONAL ANOMALIES. the impulse conveyed by the nerve-trunks; and equally futile is it to speak of one muscle as having more power, as measured by prisms, than its corresponding muscle in the other eye. The various gradations from the slightest tendency of the optic axes to turn from equilibriurn to the highest degree of permanent squint, are but steps in the same direction, or degrees of the one affection, and, in great part, the causes which underlie the one grade are found to produce all the others. For instance, a tend- ency to turn the visual axes toward each other has, as its funda- mental cause, hyperopia. The degree of inward turning or tendency is determined largely by the personal equation. Many hyperopes have absolutely no want of equilibrium, and yet others, even with low grades of hyperopia, develop marked mus- cular disorders. It has been contended that because hyperopia does not produce a squint in every instance, the squint must have some other cause, but it is well known that the same cause produces different effects according to individual characteristics. A low grade of hyperopia in a nervous or overwrought disposition will give rise to serious reflex neuroses, whereas the same degree of hyperopia in a constitution robust, strong, and resisting, will have no symptoms whatever. Again, a high grade of hyperopia is, in some, perfectly consistent with equilibrium of the muscles, while, in others, it is the cause of decided strabismus. This individuality can only be described in vague terms. It is known as a neurotic disposition, an enfeebled, unresisting nature and susceptibility to disease or an exaggeration of reflex excitability. Therefore, when all circumstances are favorable, reflex neurosis may arise from muscular anomaly, and there is no doubt that, in a few instances, the claims made by enthusiastically credulous writers are justified, but such cases are exceptional in even the largest experience, and the theory that a considerable proportion of the insane, of the epileptic, of the choreic, owe their disease wholly to the existence of either a refractive error or a consequent muscular anomaly, is dangerous and unsound. In examining patients who have no organic disease of the eye or its environment, but suffer from reflex headaches and annoyances HETEROPHORIA. 79 of various kinds, estimation of the condition of refraction and of the ocular muscles should be among the earliest findings. The investigation of the muscular status should be made both before and after the mydriatics are instilled, because of the direct in- fluence these drugs have in many cases upon both the kind and degree of the defect. The nomenclature of anomalies of the ocular muscles has re- ceived a decided impulse in the past 25 years. For functional deviations Stevens has suggested a classification that has met with quite general acceptance in America and England. It is as follows: Orthophoria, perfect binocular balance. Heterophoria, imperfect binocular balance. Heterophoria presents many varieties, namely: Hyperphoria, a tendency of the visual axis of one eye to deviate above that of the other. Hypophoria, a tendency of the visual axis of one eye to deviate below that of the other. Exophoria, a tendency of the visual axes outward. Esophoria, a tendency of the visual axes inward. Hyperexophoria, a tendency of the visual axis of one eye to deviate upward and outward, Hypoexophoria, a tendency of the visual axis of one eye to deviate downward and outward. Hyperesophoria, a tendency of the visual axis of one eye to deviate upward and inward, Hypoesophoria, a tendency of the visual axis of one eye to devi- ate downw'ard and inward. It must be remembered that, in the functional anomalies under discussion, both eyes are involved and that while the above nomenclature may describe the symptom, it does not locate the lesion. It is simply a clinical convenience. For instance, right hyperphoria means either that the right elevators are too strong for the right depressors, or that the left depressors pre- dominate over the left elevators. In other words, it simply 8o FUNCTIONAL ANOMALIES. signifies that one eye tends to turn upward or the other downward, without indicating which is the faulty eye. To this classification Savage would add cyclophoria, or in- sufficiency of the oblique muscles; and Duane, hypokinesis, deficiency of action of an individual muscle; and hyperkinesis, excessive action of an individual muscle; and parakinesis, irregu- lar action of an individual muscle. CONCERNING PRISMS. All problems that deal with the ocular muscles turn more or less upon the use of prisms. It will therefore be most profitable for the student to consider at this juncture the nature and prop- erties of prisms, so that he may the better appreciate their ap- plication to the diagnosis and treatment of functional muscular anomalies. A prism differs from a piece of ordinary plain glass only in the fact that its two sides are inclined toward each other, forming an edge or angle. Their surfaces are plane (that is to say with- out any curvature, as is met with in lenses). By reason of this A' """-^^ Angle Fig. 31. — Action of a prism on a beam of light. Dotted line indicates direction which the projected beam talces. inclination of the sides of the prism toward each other a beam of light instead of passing through it without change of general direction (as in the case of window glass) is bent from its course toward the broad end or base of the prism. For the better under- standing of the refractive properties of prisms, the student will do well to bear in mind the law which provides that as a beam HETEROPHORIA. 51 of light passes from a rarer to a denser medium it is bent toward the perpendicular, and that as it passes from a denser to a rarer medium it is bent away from the perpendicular. Thus, as in Fig. 31, if the eye be placed at B in the path of the beam after it emerges from the prism, it will not see the candle at A, its true position, but in the direction of the line BC, projected through the prism along the dotted line to A\ Hence there is displace- ment of the object in the direction of the angle of the prism and on this phenomenon is based the axiom that prisms displace the image of an object in the direction of their edge, angle or apex. If, when the eyes are directed toward an object 20 feet or more distant, a io° prism be placed, base in, in front of the right eye, it so displaces the object that the image falls to the inner line of the fovea, and, unless the eye by rotation of its cornea temporal- ward effects a corresponding inward displacement of the fovea centralis, diplopia is inevitable. The above elementary principle may be illustrated in its application to the prism test for deter- mining heterophoria or orthophoria. In Fig. 32, O is the object, OF the ray proceeding from the object to the fovea, F, of the right eye (R), and O'F^ the ray from Right retina (R). Left retina (L). Fig. 32. the same object which if not interrupted by the prism would fall upon F^ in the left eye, but a prism placed base down before that eye refracts the ray to a portion of the retina beneath the fovea. Since the lower half of the retina refers its impressions to the upper part of the field, O* will be projected above O to O^ and in a vertical line with it in orthophoria, or to one or the other side of O in lateral heterophoria. To test for hyperphoria or hypophoria the refracting prism is placed with its base in, produc- ing insuperable lateral diplopia with image of O refracted to the nasal side of the fovea of that eye before which the prism is placed; 6 82 FUNCTIONAL ANOMALIES. if hyperphoria exists, one image will be seen higher or lower than the other. According to the law of projection, if an image falls to the right of the fovea the object O will be projected or seen to the left portion of the field; if to the left, to the right portion of the field; if below, to the upper; and if above, to the lower portion of the field. In Plate 3, ^ is the fundus of an eye before which no prism is placed; B, fundus before which prism is placed base down, I representing the new position of the image in the lower half of the retina; C, prism base up; I displaced to the upper half of the retina; D, prism base in, displacing / to nasal half of the retina; and E, prism base out, displacing / to temporal half of the retina. The Relation Between Accommodation and Convergence. If there is one set of phenomena that more than any other will help the beginner in ophthalmology toward the solution of some of the obscure problems in refraction and imbalance of the ocular muscles, it is the understanding of the relation between accommodation and convergence. CONCERNING ACCOMMODATION. Since the time of Bonders, it has been known that if an individ- ual who has been shown (by the use of a mydriatic or cycloplegic) to be emmetropic, fixes the gaze on an object at infinity, there is no accommodation called into play. If the same individual be requested to look at proper sized print at a distance of one meter, it is equally well known that one diopter of accommodation is called into play.^ Similarly, to focus proper sized print at a distance of half a meter (50 centimeters or 20 inches) two diopters of accommodation * This is proven by again using a cycloplegic in the eye of such a patient, when it will be found that he can no longer read at one meter the print he read easily at this distance when the eye was not atropinized. To enable him to read the print at this distance a plus one diopter lens must be placed before the eye, thus proving that this was the amount of accommodation exercised before the cycloplegic was used. HETEROPHORIA. 83 Fig. B Fig. A i^ = fovea. / = image. No prism. / falls an F. Fig. C Prism base down. I falls below F. Prism base up. I falls above F. Fig. D Fig. E Prism base in. I falls to nasal side of F. Prism bsise out. I falls to temporalside olF. PLATE III. 84 FUNCTIONAL ANOMALIES. must be used by the patient, and to focus the same size print at a distance one fourth of a meter (25 centimeters or. 10 inches) four diopters of accommodation are demanded. It will be readily seen, therefore, that if a patient who is hypermetropic 2 diopters, focuses on print at i meter's distance, he will employ 3 diopters of accommodation (that is to say the i diopter the emmetrope Fmmefropia Ni/per/ne/fvpia^ZD M//opia 2D. Infinitif 1 Meter Wiopter % Meter ^Diopters %Meter i'Dioplers _^ Z diopte/s IMeterAny/e oDiop ZMeter/lnffles ^Diop 4MeterAnffks SDiop. 6 ^ vj /M.J. 2M.A. 4M.A. 2Diop 6 B»> IM.A. 2M.A. ■m.A 6 Fig. 33- would exercise, plus the 2 diopters the hypermetrope exercises for infinity) ; and at one-half meter's distance, the two diopter hypermetrope would utilize 4 diopters of accommodation, while at one-fourth meter's distance, the 2 diopter hypermetrope would require 6 diopters of accommodation to see the print clearly. In the case of myopia of 2 diopters, there would of course be no HETEROPHORLA. 85 effort at accommodation at infinity, nor at one meter's distance. Neither would there be at one-half meter's distance, for 50 centi- meters represent the far point of such an eye and no accommoda- tion is necessary to enable the patient to read easily. At one- fourth of a meter, however, for which point the emmetrope accommodates 4 diopters, the myope of 2 diopters would naturally exercise but 2 diopters of accommodation. The accompanying diagram may help to a clearer understanding of the principles involved (Fig. t,t,). Concerning Convergence. If vision were effected by means of one eye only, there would be no point from beyond infinity up to within a very short distance from the eye to which we could not adjust the dioptric system of that eye. But man generally sees simultaneously with two eyes, and the direction that the eyes must give to their lines of fixation in order that they may be simultaneously directed toward a point of fixation anywhere inside of infinity, is called convergence. For some years after Bonder's exposition of a precise method of estimating accommodation at various distances it was realized that when an emmetrope accommodated for an object 13 inches or 35 cm. distant from the eye, he also converged his eyes on that point, for if he did not he would surely see double. But no scheme of accurate and practical measurement of the conver- gence was in vogue until Nagel (Graefe and Saemisch Hand- buch, ist edition, Vol. VI, Chap. X) offered his ingenious unit angle known as the meter-angle. This is now commonly desig- nated as MA. Convergence is in this way easily expressed. For instance if a patient bring his gaze from infinity to an object i meter distant, he is said to have converged i meter angle. If the object be 1/2 meter (50 cm.) distant, he has converged 2 meter angles; if 1/4 meter (25 cm. or 10 inches) distant, he has converged 4 meter angles. The following table may help to an understanding of the principles involved. 86 FUNCTIONAL ANOMALIES. Accommodation diopters Convergence meter angles or MA Distance at which test; are made Infinity. I meter. 1/2 meter. 1/4 meter. It will now be readily observed that in emmetropes there is a very regular and close relation between accommodation and con- vergence. If such a patient at i meter accommodates i diopter, he also converges i meter angle. If at 1/2 meter he accommo- dates 2 diopters, he also converges 2 meter angles; if at 1/4 meter, he accommodates 4 diopters, he converges 4 meter angles. Let us assume, however, that the patient is hypermetropic 2 diopters. A new relation now appears, for if such a patient surveys an object i meter distant he converges the regular i meter angle, but he accommodates 3 diopters (the i diopter that the emmetrope would employ plus the 2 diopters he must need call into play even for infinity). If he fixes his gaze on an object at 1/2 meter, he converges 2 meter angles and accommodates 4 diopters; and if the object is at 1/4 of a meter he converges 4 meter angles and accommodates 6 diopters as shown in the diagram (Fig. 33)- Let us now assume for further illustration that the patient is myopic 2 diopters. Another relation now develops. If such a patient views an object i meter distant, he converges i meter angle, but he does not accommodate at all, as 1/2 meter (or 50 cm. or 20 inches) is the far point of accommodation in such an eye. If the object viewed is at 1/2 meter, the patient will converge 2 meter angles, but will still not accommodate at all, as this is the far point of the eye. If the object is at 1/4 of a meter, the patient will converge 4 meter angles and accommodate only 2 diopters, as shown by the diagram (Fig. ;^;^). The presence of astigmatism in combination with any spherical HETEROPHORIA. 87 error will naturally only complicate this relation; (the student who wishes to go deeply into the physics, mathematics and psychology of this relation is referred to Nagcl's original article {loc. cit.) and to Landolt's voluminous work on the "Refraction and Accommo- adtion of the Eye," translated by Culver). Enough has been said, however, to show that nature establishes for each person some manner of relation between accommodation and convergence if they enjoy binocular single vision. It will be found to be a most elastic relation subject to many changes and more or less adapt- able to varying states of refraction in the same individual. It is well for the student to realize this point, that // is the breaking in upon this relation {peculiar to each individual) that produces much of the discomfort complained of by most patients when they first put on glasses. If they have been hypermetropic (say 2 diopters) when their glasses are first worn they naturally need to use less accommodation and therefore there is less impulse to convergence, so that a certain amount of confusion is thrown into the completed visual act. In some individuals who do not readily acquire newly established coordinations and coordinate relations, this period of discomfort may extend into weeks and weeks, in which case it may become necessary to cut down the strength of the plus glass ordered and thus break in less on the relation between accommodation and convergence which had existed prior to putting on glasses. In others but a few days suffice for the establishment of new relations and they quickly become used to their glasses. The same is true in myopia and is even truer in astigmatism. So that unless the ophthalmologist is by nature a persuader of people, he will have much difllculty in carrying many of his patients through this period that is so try- ing to them, unless he bears in mind all the time the intimacy of this relation and its importance in making the final judgment as to what lenses shall be prescribed; it will suffice to say that it is the experience of the authors that full cor- rections in hypermetropes are not often well borne, this in spite of the fact that on theoretic grounds the full mydriatic correction should be given, thus establishing that relation be- 88 FUNCTIONAL ANOMALIES. tween accommodation and convergence which normally obtains in the emmetrope. As has been already said, however, if the intrusion into the patient's previously established relation be- tween accommodation and convergence is made too great and too abrupt (as it generally is by ordering the full corrections) the patient will finally conclude that the glasses are 'Hoo strong'^ and refuse point blank, in many instances, to continue any longer with them. METHODS OF DIAGNOSIS. The purpose of the various tests for the determination of muscular imbalance is to so affect the retinal image of one eye, by alterations in color, shape, or position, that the fusion-impulse will no longer be exercised, and that the tendency to deviation will become changed from a latent into a manifest one. These tests may be arranged in three groups as follows: 1. Those that displace one image. (Displacement or diplopia tests.) 2. Those that distort one image. 3. Those that neither displace nor distort either image. I. Diplopia (or Displacement) Tests. The classic test first suggested by v. Graefe is the prism test. A prism of 8 degrees, with its base down, or up, is too strong to be overcome by the muscles it antagonizes, and will produce insuper- able diplopia. For instance, to test lateral equilibrium, a prism of 8 degrees held base down before the right eye, with its base-apex line exactly vertical, will so refract the rays entering that eye that they will fall upon the lower portion of the retina, and a false image of the light will be projected into the upper part of the visual field. In orthophoria, the true (or lower) and the false (or upper) lights are in a vertical line. In esophoria, the upper image will be to the right of an imaginary line running vertically through the lower or true light. The prism displaces the retinal image of the light to the lower and (if the eye is turned HETEROPHORIA. 89 in) also to the inner half of the right retina; it is therefore projected, or seen, up and to the right. In exophoria, with the prism in the same position before the right eye, the false image will be above and to the left. The distance that the upper light is to the right or left of the imaginary vertical line drawn through the lower one, is the linear measure of the degree of the deviation. The prism (with its base out for esophoria, in for exophoria) necessary to move the upper image until it is directly over the lower one will be the angular measurement of the deviation. The principle of this test is exactly the same as that of all others — namely, the de- struction of the unconscious fusion-impulse. The individual seeing two images of the same object simultaneously accepts the impression that the two images represent two objects. Fusion having been thus destroyed, the deviation tendencyhecom.es an actual turning, and the eyes assume that position which is most restful for them and to which they are impelled by the condi- tions present in the individual case. The prism commonly em- ployed is of 8 to ID degrees. This strength is sufficient, not only to produce insuperable diplopia, but to separate the false from the true image by an interval great enough to allow slight deviation tendencies to cause a lateral displacement of the images that is instantly perceptible. Two serious errors arise when higher degree prisms are used — namely, the false image is refracted to a point on the retina so far removed from the real fovea that the findings may not accurately represent the anomaly, and the slightest turning of the prism from its axis will vitiate the result by producing artificial heterophoria. In Stevens' phorometer, instead of a single prism of 8 degrees before one eye, the effect is divided between the two eyes by means of two prisms of 4 degrees each which are held in a frame that can be rotated to test either the horizontal or the vertical tensions. (See Fig. 34.) The instrument is convenient, because both vertical and lateral imbalance can be determined by simply revolving the test-prisms into the horizontal or the vertical meridian. A total of 8 degrees is selected, because, at the distance at which these prisms are placed from the patients' eyes, muscles of average diverging 90 FUNCTIONAL ANOMALIES. power cannot fuse the double images. With the instrument fixed to test the lateral muscles, two images separated vertically will be seen. In orthophoria these images are directly in a verti- cal line, for although single vision has been destroyed, no hitherto latent tendency to turn the eyes in or out has become manifest, and the lateral muscles are said to be in equilibrium. In ex- ophoria or esophoria, one light, instead of being exactly above the other, will assume a position a little to the right or left, be- cause the eyes are now free to respond to the influence of the relatively stronger act (convergence in esophoria and divergence Fig. 34. — Steven's Phorometer. in exophoria.) The degree of prism now necessary to bring the upper image directly over the lower one, is the measure of the deviation. This is accomplished by simply rotating the lever of the Stevens instrument until the two images are in exact vertical alignment when the muscle's status can be immediately read off from the scale provided for this purpose. The lever is then car- ried around exactly 90 degrees when the test is quite as quickly made for the state of the vertical muscles (by means of lateral diplopia) and the reading taken at once from the scale. It must be remembered we are dealing, not with one, but with both eyes. For instance, in esophoria we study not one internus, but the power of convergence as contrasted with the power of divergence, and by this test we determine, in esophoria, that convergence is abnormally and relatively strong. HETEROPHORIA. 9 1 The Maddox double prism consists of two 4-degree prisms, bases together, fitted into an ordinary test glass cell and held before one eye (Fig. 35). It will cause the light as seen by that eye to be doubled (monocular diplopia). If now the other eye be uncovered, a third, which is the true image, will appear Fig. 35. — Maddox double prism. midway between the two and directly on a line with them in or- thophoria (Fig. 36). I. With the double prism placed in the trial frame two images are seen in the vertical meridian. The true, or middle image, will be out of line, to the right or left, ac- cording as there is exophoria or esophoria. 2. Let the two images Fig. 36. — Effect of a double prism on a beam of light. (Maddox.) be on a horizontal line, then the true image will be above or below this line in hyperphoria. The test is facilitated when the double prism is ground in red instead of clear glass. Another applica- tion can be made of this prism by observing whether the middle or true image is equidistant from the two false (red) ones. If not. 92 FUNCTIONAL ANOMALIES. the prism necessary to restore it to the orthophoria middle position will be the measure of both the kind and the degree of the hetero- phoria. This prism is usually applied to investigating the tensions of the oblique muscles by having the patient survey a line on a card. If they are faulty in action, the middle line is tilted up or down at the right or left. The Cobalt Test.^A glass stained with cobalt oxide and ground to fit the trial frame has the power of intercepting all the rays of the spectrum excepting the blue and the red. The image seen by the eye before which the cobalt glass is placed will be much smaller than the real image, and will have a red center with a blue halo, or a blue center with a red halo; the former in myopia, the latter in hypermetropia and emmetropia. This test has the advantage over all the others in that it does not refract the rays before they enter the eye, and in all cases the rays pass through parallel and are focused on the fovea. Hence, if deviation be discovered it must be the result of muscular insufficiency and not due to inadequacy of the method of diagnosis. The method is valuable only in cases of 2 degrees or more of vertical and 4 degrees or more of horizontal imbalance. Fusion power is largely destroyed, and in the presence of any considerable hetero- phoria the patient will see two images, one the clear or natural colored light, the other the smaller blue-red light. In orthophoria both images fall upon the fovea and the composite light will then be the clear light tinged with red and blue. In heterophoria the cobalt image will be separated from the natural image ac- cording to the kind and degree of the defect. In esophoria, for example, it will be on the side of the eye covered by the cobalt glass and on a level with the true light, the interval between them depending, as in other instances, upon the degree of the defect. In our opinion, diplopia tests (with the exception of the cobalt test) do not always indicate the true condition, for the reason that the foveal region in each retina is not considered, but rather the fovea in one eye and a point outside the fovea in the other eye. Hence, while the fusion-impulse is destroyed (which is necessary), we are expecting identical muscle-action as the HETEROPHORIA. 93 result of stimulation of different retinal areas in the two eyes. We have found that such tests are likely to show exophoria to be more frequent than esophoria, and have often found a positive contradiction between the results of these tests and those obtained by the use of the Maddox rod and other tests. The Convex SpJicrical. — A convex glass of a strength of 15 to 20 diopters, covered in all parts excepting its center, is placed before one eye in the trial frame. The image seen by that eye assumes the shape of a large blur upon the fovea and the adjoining retina. In orthophoria, the clear light seen by the uncovered eye will be situated in the center of the blurred image of the covered eye (Fig. 37). In heterophoria of low grade, the clear Orthophoria Heterophoria. Fig. 37. — The convex spherical test. image appears on the outskirts of the blurred image, and in the higher grades will be seen entirely outside of it. The space between the true light and the center of the blurred area is the linear measure of the deviation, and the prism required to refract the clear image into the center of the blurred one will be the prism measurement of the heterophoria. This test can be accurate only when but a small portion of the exact center of the lens is left clear, because rays of light passing through it at any con- siderable distance from the axial ray are refracted away from the fovea, and should an excentral portion of the lens be brought opposite to the pupil, the image of the light will not fall on the 94 FUNCTIONAL ANOMALIES. fovea. Hence, the method is open to the objection of the prism test and to the additional one that unless extreme care is experienced apparent deviation may be created by faulty use of the test. 2. Distorting Tests. The Maddox Rod (Fig. 38).— This consists essentially of a rod of glass conveniently adjusted in a disc to fit the trial frame. When light is refracted by a glass rod, a luminous point becomes a line or streak, since the rod is nothing more than a strong cylinder. As a glass rod refracts rays of light opposite to its axis Maddox simple rod. Fig. 38. Maddox compound rod. the eye will see a streak of light in the reverse meridian to that in w^hich its axis is placed. Hence, if the rod is placed vertically before one eye, the image of the light seen by that eye is a hori- zontal streak; if placed horizontally the image is a vertical streak. In orthophoria the candle-flame or point of light 6 meters distant to which the patient's gaze is directed is seen as a streak by the eye before which the rod is placed, the streak passing through the unaltered flame seen by the other eye. In heterophoria the streak is seen either to the left, to the right, above or below, according to the nature of the defect. In esophoria the streak is on the same side as the eye which sees HETEROPHORIA. 95 it. For example, a Maddox rod so placed before the right eye that the streak is vertical will be seen to the right of the candle- flame. In exophoria the conditions are reversed, the streak under the same conditions being seen to the left of the flame. In hyperphoria, the phenomenon is a little more confusing. For instance, in right hyperphoria, if the rod is placed be- fore the right eye, the streak v^ill be seen belov^ the flame; if it is placed before the left eye it will be seen above the flame; in left hyperphoria, the rod before the left eye will produce a streak below the flame; before the right eye, a streak above the flame. The prism necessary to change the position of the streak from its faulty position into the light (the orthophoria position) 6. B- / Fig. 39. — Maddox rod before right eye. a, lateral balance; h. esophoria; c, exo- phoria; d, vertical balance; e, right hyperphoria; /, left hyperphoria. is the measure of the heterophoria. This instrument is simple, inexpensive, accurate and trustworthy, especially in its latest form of the compound rod, and exceedingly useful when the student is familiar with the law of projection. The advantage of the latter over the simple rod is that no special care in its adjustment is necessary; with the simple rod it is essential to accuracy that the rod shall be in line with the visual axis. While the image is greatly distorted by this test, yet the foveal region of the retina is included in the site of the image, and we are studying the relations of the two foveas to each other, and not, as in the prism test, the relation of one fovea with a 96 FUNCTIONAL ANOMALIES. circummacular portion of the other retina. By the rod test we find esophoria more common than exophoria, and from the study of other conditions, such as the refraction, are led to believe that this is correct. For the relative positions of the streak and light in the various muscular states, see Fig. 39. 3. Tests which Neither Displace nor Distort Either Image. The Cover Test. — The patient is requested, while standing in a good light, to gaze at a small object 20 feet or more distant. The eyes are screened alternately, thus breaking up fusion. As the cover is carried from one to the other eye, no movement will be seen in orthophoria because the visual axes are parallel, but an excursion will be noticed in heterophoria. As the cover is carried to and fro, if marked esophoria be present, the eye un- covered will move in a direction exactly contrary to the movement of the cover; e.g.,\i the cover is carried from the left to the right, the left eye will move to the left, and vice versa; and the prism, base ontf before either eye that stops this movement will be the ap- proximate measure of the heterophoria. The method is appli- cable to all high-grade heterophorias of whatsoever kind, as well as the prism measure of strabismus. It does not consume more than thirty seconds in its application and should never be omitted from the study of any case. ■;.HI'LJI:U1-H^J=» ».I.I.I'»CTa: Fig. 40. — Cover for cover test and parallax test. The Parallax Test. — The preceding or cover test is entirely objective. If, however, as the cover is carried repeatedly from one to the other eye the patient is asked to state whether the object surveyed seems to jump from side to side or up and down, the test then becomes subjective and is known as the parallax test. The slightest apparent movement of the object will, after a few trials, be remarked by the patient, who accurately describes the HETEROPHORIA. 97 direction and extent of the movement. In orthophoria naturally the object will appear perfectly stationary. If the object moves in the same direction as the cover is carried, exophoria, and if in the opposite direction esophoria, is present. If the object appears to shift downward when the right eye is uncovered there is right hyperphoria, and if the reverse, left hyperphoria. This movement may be completely controlled by prisms, and the degree of prism which stops the movement is the measure of the heterophoria. This test is susceptible of extreme delicacy, deviations as slight as one-eighth of a degree being measurable in some instances. Fig. 40 illustrates a convenient cover with handle for use in this and the preceding test. In general terms it may be said that those tests which are at the same time the most accurate, the simplest, and require the least apparatus, are the ones most likely to lead the beginner to the surest results. For this reason the Maddox rod (compound) and the cover and parallax test are trustworthy, although the phoro- meter has many warm advocates. The cover and the parallax test have the great advantage of finding the eyes just as they are and *as the patient uses them all day long and is least likely to create any factors of error. On the other hand, the phorometer is easy and quick of application and very helpful to the novice in indicating for him the kind and amount of deviation present. Tests for the Reading Distance. The Dot and Line Test. — The principle is exactly that described for the prism test at 20 feet. It was devised by v. Graefe for testing insufficiency of the interni only. A prism of 8 degrees is placed base down, before one eye. The patient gazes at a small black dot, through which a line is drawn, on a card held at the ordinary reading distance (Fig. 41). If the prism is placed base down before the right eye, the two dots will be seen on the same line in orthophoria. In lateral insufficiency both dot and line will be doubled, the upper belonging to the right eye. The false image will be to the right (esophoria) or to the left ^i^. 41. 7 98 FUNCTIONAL ANOMALIES. (exophoria) according to the lateral deviation. In hyperphoria, with the test-card and the prism changed from the vertical to the horizontal position, the false dot and line will be above or below the true dot and line. In balance of the vertical muscles the false and true dots will be on the same vertical line. In our judgment, the dot alone forms a superior test, since the line maintains, in part at least, the desire for fusion and serves, in a measure, to prevent independent movement of either eye. A small printed word may be similarly employed. The Maddox test for the reading distance, based also upon prism displacement, provides a scale for the measurement of the angular deviation without other means (Fig. 42). fo's° 8° T e's" 4' i T 10' 9' 8' 7' G' S' t' S' Z' 7 r z'3' -■to -60 Fig. 49. — Scale for tropometer. The field of binocular fixation comprises that part of the visual or form fields that is visible to both eyes at the same time without movement of the head, but with movement of the eyes. It is not necessarily identical with the field of binocular single vision, although the limits are practically the same. Near the periphery of the field of binocular fixation, the images of the object may not fall upon the yellow spot of each eye, but upon adjoining portions of the retina, when insuperable diplopia will be mani- fest. The field of binocular vision is smaller than the united 112 FUNCTIONAL ANOMALIES. fields of each eye, and that of binocular single vision is still smaller. The limits of both may be readily determined by peri- metric measurement, using one or two small white dots on a black background or black dots on a white background. Those dots on the periphery where the single dot doubles or blurs, represent the limits of the field of single vision. They are approximately : Up 60 degrees (Pooley) 45 degrees (Duane). Down. . 70 degrees (Pooley) 70 degrees (Duane). Right and left 60 degrees (Pooley). .55 degrees (Duane). In old age the rotations are lessened, and in determining them at any age, the form and position of the globe in the orbit and Fig. 50. the orbital bones must be taken into consideration. Such wide variations as are shown in the averages given above are confusing HETEROPHORIA. II3 to one who endeavors to determine whether a certain movement is normal or otherwise. An excess of t,t, degrees upward or of 55 degrees downward rotation should direct suspicion to the vertical muscles, and if, in the presence of esophoria or exophoria, the temporal and nasal rotations are normal, operation on the lateral muscles will scarcely be recommended and is justifiable only when the vertical muscles have been exonerated of causative influence by careful estimation of their rotations; this is especially important because high-grade lateral deviation tendencies are often an indication of unequal vertical tensions. It may be well to note, in passing, that the surgeon may learn by means of the tropometer the peculiarity of his own muscular status with re- spect to the horizon before proceeding to the use of the clinoscope (Fig. 50), also devised by Stevens, for accurate study of the horopter in all cases of anaphoria or anatropia, also cataphoria or catatropia.^ In case the observer is exophoric or esophoric, the tubes may be adjusted in divergence or convergence, and in case of hyperphoria a correcting prism may be placed in a clip next the eye.- ' Anaphoria. Latent deviation of both visual axes above the horizontal plane of the head. Cataphoria. Latent deviation of both visual axes below the horizontal plane of the head. Anatropia. Manifest (apparent) deviation of both visual axes above the hori- zontal plane of the head. Catatropia. Manifest (apparent) deviation of both visual axes below the hori- zontal plane of the head. ^ Monocular diplopia is the result of irregular corneal or lenticular curvature, or of disease of the foveal region, and bears no relation to the subject under discussion. ESOPHORIA. Symptoms. — The symptoms of the tendency of the visual axes toward each other are local or ocular, and general or retlex. They vary according to the degree of the esophoria and the sus- ceptibility of the patient. The local symptoms are in no wise distinctive. They are : Pain in the eyes and in their immediate neighborhood, flushing of the conjunctiva after use, photophobia, lacrimation, blurring of the print in reading, and inability to continue for any length of time the effort of looking at near or distant objects without becoming drowsy. As will be seen, the same symptoms may depend upon hyperopia or astigmatism, or any other muscular or refractive error. The reflex symptoms are exceedingly complex and unstable, and they vary from an occasional slight headache to intense migraine; from a simple restlessness to serious functional nerve-diseases, from a chronic insignificant disturbance of digestion to loss of appetite, inter- rupted digestion, and vomiting. A peculiarity of esophoria, not found among symptoms of refractive or other muscular anomalies, is that the patient often complains of seeing his nose, especially in close work. This symptom is largely imaginary, for the patient is no more inclined by esophoria to turn his eye in so far that coordination will be lost, than he is to have double vision for all objects. The complaints are not limited to the time of using the eyes, but often follow for many hours after a continued or unusual strain. Identical symptoms, although perhaps not so severe, arise from gazing intently in the eft'ort to see clearly a distant object. Esophorics invariably are disturbed by traveling in the train, by looking at rapidly moving objects, by shopping, and after the theatre or opera. The symptoms are due, not directly to the internal muscles, but to the constant 114 ESOPHORIA. 115 effort under which the patient labors to prevent abnormal con- vergence. A tendency inward can be controlled only by an equiv- alent tension on the muscles of divergence. If the defect is so high that the external muscles cannot constantly maintain coordi- nation of the visual axes, and one eye turns inward, the symp- toms may be immediately relieved, but the patient will complain of diplopia. It is not always the highest degree of defect that gives rise to the severest symptoms. The disturbances above described never arise, for instance, in cases of manifest internal squint. It can be readily understood that the constant strain on the ab- ductors to maintain parallelism of the visual axes may give rise, in certain subjects, to alarming reflex neuroses. No set of muscles, in any part of the body, can be in a state of constant contraction without making a deep impression on the nervous system. Indeed, hypnotic states are induced through an analogous process. The severity, then, of the symptoms must depend almost entirely upon the susceptibility of the individual to abnor- mal impressions, and the patients who suffer most in esophoria are those who habitually complain severely from apparently insignificant causes. Etiology. — The causes that contribute to the abnormal ten- dency of the visual axes inward are local and constitutional. In many cases, it is quite impossible to satisfactorily explain the origin or the existence of esophoria. It may be stated, however, in general terms that it is found most frequently in persons of a neurotic disposition who have low grades of H. Ah or H. The susceptibility of the nervous system plays a most important role in the causation of muscular anomalies, particularly esophoria. By that expression is meant an abnormally acute impressionabil- ity of the nervous system induced by lack of proper nourish- ment from deficiency of oxygenated blood, a stasis of the venous or arterial supply from disturbance of the circulatory system — in short, a neurotic disposition. That an underlying predisposi- tion to irregular nerve-activity is an essential contributing factor in the development of the muscular imbalance and the symptoms accruing from it is demonstrated by the well-known fact that many Il6 FUNCTIONAL ANOMALIES. individuals, who have the theoretic local conditions assumed to give rise to muscular asthenopia, use their eyes constantly without discomfort; furthermore, in the absence of the local causes that are conceded to produce esophoria, and in the pres- ence of those that are usually causative of exophoria, esophoria is often present and gives rise to no symptoms. Identical in- consistencies are illustrated in the study of the etiology of other than eye diseases. Two persons exposed to the same influences will be seized with different affections or one will entirely escape. It is not strange, therefore, that we are often at a loss to ascribe the mysterious unbalancing of the ocular muscles to a competent cause, and are compelled to invoke the aid of the supposition of a deranged nervous organization. The interdependent, constant, tenacious relation between the intra- and extra-ocular muscles furnishes an explanation of the existence of esophoria in a majority of cases. In health there is a certain related range of accommodation and convergence; every contraction of the ciliary muscle is accompanied by contraction of the adductors, or stimulus to the accommodation means stimulus to convergence. In emmetropia the meter-angle of convergence is determined by the diopters of accommodation. Thus, accommodation of 3 diopters induces convergence of 3 meter-angles. Now if, for any reason, an abnormal amount of accommodation is required to read at the ordinary near point (thus overstepping the normal range) a correspondingly increased demand on convergence is made, and a tendency to converge the visual axes to a point within the desired reading distance results. When, notwithstanding this unbalanced relation, the normal con- vergence of the visual axes is maintained, it can only be at the expense of the relative accommodation and convergence, and in any case it entails an unusual resistance on the part of divergence. If the range of the relative accommodation and convergence is not exceeded in this effort to secure binocular fixation at the read- ing distance, there will be no esophoria and no symptoms, and this probably explains the exemption of certain individuals. The refractive conditions that most frequently give rise to a disruption ESOPHORIA. 117 of the relative range are hyperopia, hyperopia astigmatism (simple and compound) and low myopic astigmatism. To over- come hyperopia states of the refraction and thus secure good acuity of vision for both distance and near, unusual demand is made on the ciliary muscles, which in turn stimulates all the other muscles supplied by the 3rd nerve. Hence, an inward tendency of the visual axes is originated, but this, in the interest of binocular single vision, is suppressed and the condition remains a tendency only. The same reasoning applies to hyperopia astigmatism; myopia astigmatism of low grade is also a frequent and potent cause of ciliar\^ spasm, and thus may be classed among the causes of esophoria. Treatment. — WTien, by means of one or all the tests described on page 88, inward tendency of the visual axes has been repeatedly and conclusively determined, we are confronted with the practical problem of relief. The method selected depends upon i, the severity of the symptoms, and 2, the degree of the esophoria. We recommend the adoption of the following course: First. Use of a Proper Correction. — In all cases the estimation of any optical defeat under complete paralysis of accommodation and the wearing, for some weeks, of as nearly a full correction as can he home with comfort. This is essential. No other treat- ment directed to the restoration of the lost equilibrium of the muscles should be inaugurated until glasses correcting the ame- tropia have been worn sufficiently long to remove any pernicious influence born of constantly over-taxed accommodation. The experience of all ophthalmologists confirms this statement, and no surgeon of judgment or ability will apply treatment directly to the muscles until he has given the patient the opportunity to be cured by wearing glasses. Any co-existing general distur- bance must also be relieved by appropriate medication. Diet should be regulated, exercise in the open air instituted, the time devoted to reading restricted; in short, every means tending to diminution of the unwonted excitability of the nervous system, or the derangement of any of the vital functions, must be employed. Second. Convergence and Accommodation Repression. — Inas- ir8 FUNCTIONAL ANOMALIES. much as excessive accommodative effort is a chief agent in the production of annoying esophoria, it is well to try to remedy the abnormal convergence effort by quieting the overactive accom- modation if possible. Should the use of a proper correcting glass prove insufhcient to allay the patient's symptoms, resort may be had to the use of a plus 2 or 3 diopter spherical lens to be used in addition to the regular correction by means of a hook front or other device. With this the patient w^ill read or sew for 15 minutes to half-an-hour, two, three or four times a day for two to four weeks. Complaint will of course be made that the read- ing or sewing must be brought very close to the eyes, but if the patient is reassured he will generally persist. Some drift readily into the practice, some with difficulty and much persuasion, and some never. It will seldom be necessary to resort to it save in esophoria of 6 degrees or more. In some cases the results are peculiarly gratifying and in others are a total failure. Third. Prism Exercise and Nerve Sedatives. — By means of frequent and interrupted use of prisms, we endeavor to strengthen the power and increase the range of divergence, and unless there is actual preponderance of convergence, some cases of recent standing may be effectually treated by this method. Abduction normally equals 7 or 8 degrees w^hen tested with a candle at 20 feet. In esophoria, abduction sometimes falls to I, 2, or 3 degrees, and the normal ratio between abduction and adduction (about i to 3 or 4) is lost. A prism of 6 degrees, axis horizontal, is placed base in before the patient's eye, and the patient is instructed to look at the candle-flame 20 feet distant. If his abduction equals 3 degrees, the prism will produce insuper- able homonymous diplopia; but if he advance to within a few feet of the candle flame, abduction increases as he advances, and he will reach a point where the two lights will fuse. He now re- cedes from the candle, maintaining its image single as long as possible. When the images have again separated he approaches the candle until the lights are fused, when he again recedes. This may be repeated a number of times, but no longer than five minutes at one sitting. On the second trial he will find that the ESOPHORIA. 119 C lights fuse easier than at the first. At the third trial it will be still easier, and in the course of a few days he will be able to fuse the lights at 20 feet. This exercise should be continued until asthenopic symptoms have disappeared for some weeks. The prism may be placed before either eye, or before one and then the other, and the effect will be the same. Fusion of the lights is not the result of contraction of one or the other externus alone, but is accomplished by forced action of all the muscles which partic- ipate in divergence — an extremely complicated function. (See Weiland's article in Arch, of OphthaL, January, 1898.) In our experience, however, prism exercise has quite as often aggravated the symptoms as it has relieved them. ^ A useful adjunct to the prism exer- cise is the internal administration of the tincture of belladonna, hyoscya- mus, bromides, or some of the other sedatives, in as large doses as can be well borne. The effect of these remedies is to diminish the spasm or abnormal contraction of the ad- ductors and benumb the sensitive- ness of the nervous system. Fourth. Correction by Prisms in the Position of Rest. — When, after appropriate trial by means of the above remedies and methods, it is felt that something must be done, and operation is out of the ques- tion, the symptoms may sometimes be relieved by the use of prisms, bases out, which correct a portion of the esophoria (Fig. 51). The degree of the defect requiring the use of prisms varies from 6 to 15 degrees. Defects under 6 degrees may fre- quently be corrected without them, while those higher than 10 degrees sometimes necessitate operation. The degree of the de- fect is determined in every instance by the result of testing at 20 feet. A constant relation does not exist between the convergence Fig. 51. — Effect of diverging prisms on excessive convergence. I20 FUNCTIONAL ANOMALIES. for distance and for the near point in cases where equilibrium has been lost. For instance, a defect of 7 or 8 degrees for distance may be the same, or less, or more, at the near point, depending upon various concomitant conditions. The strength of prism should be much less than the total amount of defect. It is well for the novice to feel his way and not order more than i degree of prism base out in each eye as an experiment. It is a question whether wearing a prism correction does not develop an increase in the error; the very principle of its action forbids a cure. Under such treatment the tendency of esophoria is to increase, but whether this increase is due directly to the effect of wearing the prisms or to the unmasking of a latent defect is uncertain. Should the general health be improved by medication, change of environment, or oc- cupation, etc., the defect may become less, but not often can this improvement be ascribed to the prisms. It is oftener the case that stronger and stronger prisms will be required to relieve the symp- toms, and occasionally the case comes to operation. Our plan is to allow the patient to wear his prism correction without change as long as he is comfortable, permitting him to decide whether it shall be worn constantly or only for near work. In most instances, constant wearing only will give relief. It must be remembered that esophoric patients do not complain of headache or other symptoms consequent upon prolonged use of the eyes at the near point only, but intense gazing at objects in the distance, such as the preacher in his pulpit, looking steadily from a car window, or gazing at objects that are themselves moving, will give rise to these symptoms. The directions to the patients should be modified according to their occupation and symptoms, allowing them to judge as to the occasions when it will be necessary to wear the glasses. The following case is in point : F. E., aged ten, is referred by his family's general medical adviser, who has exhausted his resources in endeavoring to quiet the boy's blepharospasm and general nervous irritability. Cir- cumcision had been done and adenoids removed in hope of benefiting him, but without avail. The child was undersized for his age and the son of a neuropathic father and a gela- ESOPHORLV. 121 tinous mother. His vision equalled 5/5 in each eye; his accom- modation was normal. Esophoria of 10 degrees was present and no hyperphoria. Under atropin refraction was found to be + 2.00 sph. in each eye. Because of his esophoria + 1.75 sph. was ordered for constant wear, but the child absolutely refused to wear the glasses because of blurred distant vision; +1.25 sph. was therefore ordered arid worn with some relief to the symptoms, but six months later at the end of the school year the blepharo- spasm was as bad as ever. Convergence and accommodation repression were then tried, but as the family offered no cooperation it was finally decided to combine a i degree prism base out in each glass with the +1.25 sph. In four weeks the blepharospasm had entirely disappeared and in four years has not reappeared. Today, after four years, he wears a 2 degree prism base out with + 1.50 sph. in each eye. His total esophoria is 12 degrees, an in- crease of but 2 degrees in four years and the boy is growing finely and does his school work without any complaint whatever. It is quite possible that after he passes through puberty, the prisms may be taken out of his glasses and accommodation repression be invoked to allay any symptoms he may develop. Prisms in the position of rest give relief because, while worn, the patient's eyes are allowed to assume a position W'hich is one of rest for them, and objects are held single by the refracting power of the prisms. In esophoria the visual axes have become converged, and prisms, bases out, bend the rays proceeding from the object outward toward the new position occupied by the fovea centrales. Here the position of rest is not parallelism, but convergence. The tendency to turn has become an appreciable turning. Prisms must be regarded as crutches that will permit the patient to travel comfortably over his rough road, rather than as a means of final cure. Fifth. Operation. — ^In all cases operation should be reserved as the last resort. In low grades of esophoria — in fact, in all grades of esophoria not bordering on esotropia, the means recom- mended under paragraphs i, 2, 3, and 4 should be given a proper trial and cannot be too much emphasized. Some writers go 122 FUNCTIONAL ANOMALIES. even farther than this and state that no benefit whatever is derived from operation. Our experience does not justify this statement. We are convinced that many cases are operated upon that could be relieved by less radical measures, and, on the other hand, we have operated where other means have been tried and failed and have been entirely successful. The measure of success is the cessation of the symptoms and the restoration to equilibrium of the muscles. The condition known as equilibrium varies, as has been before noted, from esophoria of 2 degrees for 20 feet, to exophoria of 2 degrees for the reading distance. But it is our opinion that equilibrium or orthophoria is present only when, by testing with the Maddox rod, the streak of light passes directly through the center of the flame horizontally and vertically. Having decided that surgical procedure is necessary, we have the choice of advancement of the external recti or tenotomy of the interni. According to Landolt, tenotomy is never in place — advancement is the only surgical means. He bases this opinion upon the assumption that, in all cases, "the defect arises from a loss of divergence and not an increase or spasm of convergence; hence a weakening of the muscles which are not too strong is wrong in principle." If esophoria depends on hyperopia or hyper- opic astigmatism — in other words, if the abnormal convergence is a reflex from unusual activity of the accommodation, the tendency of the visual axes inward is not a result of an insufficiency of diver- gence, but a physiologic sequence to inordinate action of the ciliary muscle, producing excessive convergence. Hence, in esophoria, tenotomy of the interni is more often productive of good results than advancement of the externi. Moreover, adjustment of the ocular axes is much more precise with tenotomy than with advancement. All such operations should be done under local anesthesia, so that the patient maybe brought to the sitting posture and the final result controlled by some one of the tests alluded to. It is not practicable to state in precise terms the exact degree of esophoria that demands or justifies tenotomy or to make an arbi- trary law, any more than it is reasonable to say that in hyper- metropia a certain number of diopters or fractions of a diopter ESOPHORLV. 123 must be deducted from the full correction. The decision as to operation depends upon the effect of the methods of treatment previously outlined and on the severity of the symptoms. If we find that under accommodation repression, prism exercise and internal medication the defect remains unchanged or slightly improves, and the symptoms become less and less annoying, even though the degree of esophoria be moderately high, operation is not to be recommended. And, on the other hand, if a moderately low degree is associated with severe symptoms and only partial relief results from the wearing of prisms, operation is to be con- sidered. In our own practice we are generally guided by the severity of the symptoms. After other means have been faithfully tried and failed, esophoria of more than 10 degrees will at times demand surgical interference. Prisms of more than 4 degrees in each eye cannot, as a rule, be comfortably worn. Moreover, prisms are changeless and constant in their refraction, while the muscular conditions of the eyes are changing and inconstant. We are attempting to correct a live physiologic function by means of a dead, unalterable piece of glass. The degree of esophoria varies as above stated — in fact, different estimates may be reached by different observers at the same examination, therefore, allow- ance for this variance must be made in the prism correction. After operation and consequent reduction of the degree of esoph- oria the conditions are often more amenable to prism treatment. Should the operation be limited to one eye or should both be included? We are dealing either with excessive convergence or defective divergence, and in either case we have to do with more than one muscle and more than one eye. Theoretically, therefore, the operation should be divided between the two eyes, unless we have reason to believe that the esophoria is the result of an organic muscular change, limited to one eye, or is due to a nebula of the cornea, to high-grade optical defect, to vitreous or lenticular opacity, or to some impairment of vision, indicating that the esophoria proceeds from a local cause and is not the result of disturbance of innervation, Heterophoria is rarely met with in cases where organic imperfections of one eye lead to 124 FUNCTIONAL ANOMALIES. manifest squint, and usually to amblyopia of high degree, and may therefore be excluded from consideration in this chapter. We are concerned with patients who suffer from no incurable affection of vision, have no organic lesion that can be determined, and who have, as a rule, fair acuity of vision in both eyes. We cannot, therefore, admit that the tendency of the visual lines in- ward is a monocular affection and that its treatment is conse- quently monocular. In all cases both eyes should be made to share the treatment as nearly as possible. Where double opera- tion does not seem to be indicated, the symptoms can be relieved by the other means suggested without operation. It is a debatable point whether both eyes should be operated on at the same sitting or the second operation follow several days after the first. The points in favor of the former are, that under antisepsis the surgical procedure is free from danger; the incision is extremely small, involving but few tissues and these are superficial; the pain is insignificant and confined to the drag- ging forward (either by the hook or forceps) of the tendon and the cutting of its fibers; hemorrhage is unworthy of mention, the subsequent discomfort is little if any more after the double operation, the rotation of each ball is similarly and contemporaneously in- fluenced; and finally the patient is gratified that the performance is com- pleted. The advantages of the single operation are: less immediately subsequent annoyance; and the possibility that it will suflice for a cure. But such advantages are not worthy of serious consideration when compared with those of the dual operation. The progress of the operation must be marked by measurement of eft'ect according to the change in position of the images of the candle-flame at 20 feet or of the streak if the Maddox rod is used. As often as necessary, the operation must be suspended and the result of the section of a few fibers determined, otherwise the operator is in the dark and his result is Fig. 52. ESOPHORLA. 125 only approximate. In performing this operation it is well after dividing the conjunctiva to pick up the tendon of the internus with a forceps instead of a strabismus hook and simply button-hole it (Fig. 52). Further cautious divisions may be made above and below according to the indications furnished by the Maddox rod. Vo/fCR.A£f£ J 86 1. I^x VmGRA£F£ 186/. ABADIE. ZIEGLER. 1880 K STEVENS. 1883. 189/. VERHOEFE 18 93. TODD. 1907. Fig. 53-- -Various methods of doing partial tenotomy. Ophthalmology, April, 1911-) (Ziegler, Annals of In this way every fraction of result secured from the division of even a few^ fibers may be most accurately studied, and overefTect avoided. In Fig. 53 various methods of doing partial tenotomy are portrayed. Our own preference is for the method of Stevens, although that of Ziegler has much to commend it. EXOPHORIA, For a long time it was held that exophoria was a purely passive condition resulting from diminution of the convergence impulse, but this conception must now be modified. That a certain per- centage of all cases of exophoria does represent a passive or under action phenomenon (in reality an accommodative exophoria) is a thoroughly established fact. On the other hand, in a series of 441 cases of exophoria^ it was shown that in 72 per cent, of the cases there was an associated H + Ah refractive status; and inasmuch as all hypermetropic conditions call for excessive accommodation impulse (hence associated excessive convergence) some factors other than subnormal accommodative impulse must be invoked to explain this association. Moreover, the term exophoria (like esophoria) while of great clinical convenience, is not alto- gether sufficient to the purpose for which it is employed, in that it gives no clew as to whether convergence be deficient, divergence excessive, or both divergence and convergence deficient. For purposes of study, therefore, exophoria may be arranged in four classes : 1. Exophoria with subnormal accommodative power (generally allied with an M + Am refractive status, the old classic conver- gence insufficiency of Donders, von Grsefe and Landolt). 2. Exophoria (in the presence of H -fAh) with normal diver- gence and deficient convergence. 3. Exophoria (in the presence of H-f Ah) with normal con- vergence and divergence excess. 4. Exophoria (in the presence of H-j-Ah) with convergence and divergence both deficient. Concerning exophoria with subnormal accommodative power it may be said that the cause is a myopic error of refraction. In ' Journal of the American Medical Association, 1906. 126 EXOPHORIA. 127 myopia and myopic astigmatism of two or more diopters, the demand on the accommodation, when reading or otherwise using the eye at the usual near point, is less than in lower errors of refraction, since the lens, already too convex to bring parallel rays of light to a point on the retina, is adapted for a distance inside of infinity, and the higher the myopia, the nearer to the eye is its far point, therefore the less need for contraction of the ciliary muscle. The muscles of conver- gence, deprived of the impulse associated with ciliary contraction, are handicapped and respond to the impulse to convergence only, instead of the impulse to convergence and accommodation. When we consider that vision at the reading distance is de- manded by the majority of the human family hundreds of times daily, the final effect of such an insufficient innervation may be readily appreciated. After months or years a distinct loss of impulse results and exophoria appears. According to this reasoning the degree of exophoria has a distinct ratio to the grade of myopia, and, other things being equal, this is the true state of the case. Indeed, it is rare to find equilibrium of the ocular muscles and still rarer to find esophoria among myopes, for the same reason that esophoria is common among hyperopes. Symptoms. — Patients with exophoria are quite likely to be neurasthenic to a greater or less degree, so that their description of all their symptoms is subject to a certain discount. Headache. — Naturally this is the predominant symptom, especially when it persists after wearing a good correction. An analysis of the headaches complained of by 173 exophorics shows that the frontal type was present in 102, the occipital type in 60 and the temporal type in 11. These headaches are more or less constant, exist independently of use of the eyes for near work, and are exaggerated by near work, also anything which calls for much quick adjustment of the eye muscles, such as railway and trolley journeys, moving in a crowd, and shopping. On the other hand, anything which calls for prolonged steady fixation, such as attendance at the theatre or gazing fixedly at the preacher in his pulpit, produces the same effect. Particularly 128 FUNCTIONAL ANOMALIES. trying to such patients is an expedition to a picture gallery, as the gaze is generally directed upward and exophoria has a tendency to become greater as the eyes are turned upward. Of 200 exophorics in private practice, 140 gave testimony as to more or less vertigo, especially after near work. This particular vertigo may not be greatly annoying as it is of the most transient character, but the patient so seldom associates the symptoms with their ocular status that it will be elicited only by questioning. Ocular fatigue was present in 153 of the 200 cases, ocular tender- ness in 98, conjunctival irritation in 121, and low grade photopho- bia (or glarophobia) was in evidence in 130. Nausea of a tran- sient kind seemed fairly well related to the exophoria seventy-two times and drowsiness after near work, especially at night, was almost a constant symptom. In twenty-three cases gastric reflexes were admitted. By this is meant a nameless vacant sensation in the epigastric region. That a certain percentage of exophorics (who overcome their exophoria) have this reflex is indisputable. Two cases presented intractable superior dental neuralgia (with teeth in perfect condition) that yielded to treatment for the associated exophoria. It will, therefore, be seen that the symptoms are variable indeed, and just as with an uncorrected refractive error, they may be direct or remote, and may be almost individual or may appear in groups. Diagnosis. Diplopia Tests. — A prism of 8 degrees is placed base down before the right eye, the patient gazing at a candle flame 20 feet distant. The upper image is the false one and be- longs to the right eye. It is not directly above the true image, but is above and to the left. The prism base in before either eye that brings the two images directly in a vertical line is the measure of the exophoria. The phorometer of Stevens is a much readier application of the same principle, and by rotation of its lever the character and amount of the exophoria are shown at once. Cobalt Glass Test. — In high-grade exophoria, diplopia will be produced by holding a cobalt blue glass in front of one eye, the image seen by which will be blue-red and smaller than that seen by the uncovered eye; the cobalt image will lie on the side opposite EXOPHORIA. 129 to the eye before which the glass is placed, the separation depend- ing on the grade of exophoria, expressed in terms of the prism, base in, necessary to fuse the cobalt and the true image. Defects of less than 3 degrees are, as a rule, not uncovered by this test. Distorting Tests. — Of most value is the Maddox multiple rod. If it is so placed before the right eye in the trial frame that a vertical streak appears before that eye, the streak will fall to the left of the candle flame; and to the right if the rod is placed before the left eye; that is, the images are crossed. The prism base in before either eye that will displace or carry the streak directly through the flame represents the degree of the defect. Cover and Parallax Test. — The patient gazes at a small brilliant object 20 or more feet distant. The eyes are screened alternately, thus breaking up fusion. As the cover or screen is carried back and forth from one to the other eye, the uncovered eye will move in toward the median line because while under the cover it has rolled out into the position most restful for it. The prism base in before either eye that will arrest the movement of the eyes is the measure of the exophoria. This test is wholly an objective one and its objectivity and accuracy give it great value. It does not consume more than one minute in its application and should never be omitted from the study of any case of exophoria. If it is desired to make it subjective by asking the patient after a few movements with the card whether the fixation object appears to jump from side to side as the card is shifted this is readily done, and so carried out becomes the parallax test. The prism base in before either eye that arrests the apparent jump of the fixation object is the measure of the deviation. This test is of the greatest delicacy, one-fourth of a degree of deviation being easily possible of de- tection in intelligent patients. Tests for the Reading Distance. — In no class of cases will tests at the reading distance be more serviceable than in exophoria. For this purpose we have discarded the dot and line test, and use almost entirely the multiple Maddox rod and a small one candle electric light. The patient holds the light at the ordinary read- ing distance (about 13 inches) and the state of the muscles at 9 130 FUNCTIONAL ANOMALIES. that point is estimated, the patient's correction invariably being worn- during the test. In presbyopes the reading correction should be used when the test is applied or the observer may be led into error. S-child's, Baer's or any other modification of the apparatus just described may be used. Too much stress cannot be laid on this test in exophoria, as is illustrated by the following fairly typical case: J. G., thirty-five, accountant, complains much of ocular dis- tress after working two to three hours consecutively over accounts. He had been carefully refracted three months previously and ordered a suitable correction. At that time exophoria of i degree for infinity had been noted. Estimation of the muscle status at his working distance revealed exophoria of 11 degrees and no hyperphoria. The convergence near point was 5 inches (12 1/2 centimeters). The abduction was 8 degrees and the adduction 12 degrees. He was given convergence training which improved the condition somewhat. Finally a i degree prism base in each eye was incorporated in his regular correction and this prismatic glass ordered for his work at accounts only. Within four weeks all his ocular distress had disappeared. Supplementary Tests. Prism Cofivergence. — As has been noted in a previous chapter, prism convergence is such a vari- able factor that it may prove misleading if too much reliance is placed upon it. Yet it will often elicit some interesting informa- tion and should be estimated in all obscure cases. In general terms there should be at least twice if not three times as much prism convergence as prism divergence in all but high degrees of exophoria. Prism Divergence. — Prism divergence is commonly a com- paratively fixed quantity and if found to be 6 or 8 or 9 degrees at any one sitting it is fairly sure to measure the same at any future sitting. It, therefore, becomes a factor of marked value. Usu- ally it is not found to be more than the normal 7 degrees. The Convergence Near Point. — In every case of exophoria this element is of paramount importance, Landolt many years ago devised for the ready estimation of the convergence near point EXOPHORIA. 131 his ophthalmodynamometer (see page 106) which is of much service. For the last eight years we have employed for the same purpose the tiny electric light of the De Zeng electric ophthal- moscope. With the room half darkened, and starting at 15 inches from the face, the patient watches the light attentively as it is carried in the median line closer and closer to the face. At about 10 inches from the eyes the bright small corneal images from the electric light become plainly visible to the surgeon and it is easy to watch the behavior of these images as the light is carried toward the root of the patient's nose until one or the other of the corneal images shows that the eye to which it belongs is no longer being converged. This is the near point of convergence and one can thus readily calculate the number of meter angles of positive convergence at the patient's disposal. For instance, if the eyes refuse to converge inside of 4 inches there are 10 meter angles of positive convergence; if they refuse at 5 inches there are 8 meter angles; if at 3 inches there are 13 meter angles. The test as thus applied is objective, while Landolt's proceeding is subjective and open to all the disadvantages of every subjective test; it is rapidly applied and of proven value. If we now divide the prism divergence (previously estimated) by 7 and add the quotient to the positive convergence we shall have the total amplitude of convergence. Usually the average patient has from I to I I /2 meter angles of negative convergence (prism divergence) hence the calculation becomes very easy. Thus: Fannie G, aged eighteen, shows 3 degrees of exophoria for dis- tance and 15 degrees for the reading distance. Her prism divergence is 7 degrees (equals i meter angle of convergence) and her convergence near point equals 8 inches — that is, meter angles of positive convergence. Hence her total amplitude of convergence is but 5 positive and i negative or total 6 meter angles. Inasmuch as anyone who wishes to use his eyes much at the reading distance should have at least 1 1 meter angles of convergence amplitude (that is to say a convergence near point of at least 4 inches) it is needless to say that this young woman had great difficulty in using her eyes for any reading, writing or 132 FUNCTIONAL ANOMALIES. sewing. In some cases of exophoria, the tropometer will be of value in determining whether both eyes share equally in the deviation (innervational exophoria) or whether one eye is mark- edly deficient in its adducting power as compared with the other (anatomic exophoria). The four principal tests in the study of all exophorias are : a. the exophoria for infinity (or distance) ; b. the prism divergence; c. the exophoria at the reading distance, and d. the convergence near point. There are many supplementary tests that may be used to advantage, but knowledge of the four facts just mentioned is essential for the proper treatment of any case of exophoria. In all cases of exophoria the various tests should corroborate each other closely, in which case no difficulty should be experi- enced in arriving at the conclusion that the visual axes have a ten- dency away from each other. Here again, much as in esophoria, we are dealing with the relation between divergence and conver- gence and (with the exception of the anatomic cases) not with the externus or internus of one or both eyes, but with the diverging power of the externi and the obliques as opposed to the converg- ing power of the interni, assisted by the vertical recti. Finally, no test for exophoria is reliable that is instituted any time within twenty-four hours of the time that a mydriatic is used in the eyes for the same reasons set forth in the chapter on Esophoria. Tests should be made before the mydriatic is used, and if with the mydriatic effect in the eyes not until the mydriatic has been exerting a constant effect for two to three days. Treatment. — The treatment of exophoria (or latent diver- gence) calls for much discrimination. I. As most of such patients are more or less neurasthenic (as has been already pointed out), too much emphasis cannot be laid upon the value of right living. This implies moderation in all things (including diet, smoking, drinking and all other daily life habits). Hydrotherapy, either by means of warm baths before retiring or a quick cold sponge on arising — preferably the latter— is often of service. An additional hour or two of sleep will at times prove the saving measure. EXOPHORIA. 133 2. The Correction of the Error of Refraction. — This reiteration may become wearisome, but the authors concede that the great proportion of muscular insufficiencies are directly or indirectly originated by ametropia, and believe they would be remiss in their duty unless they insisted on every opportune occasion that treatment should be invariably inaugurated by correction of any optical defect that may be present, for the double reason that the optical defect may be the sole source of the muscular symptoms and its correction may prove the cure of the same; further, no restoration to equilibrium can be expected when the cause thereof is acting. In exophoria associated with H + Ah it is the part of wisdom to undercorrect the spherical element of the refractive error by anywhere from +0,50 to + i.oo sphere according to the degree of the deviation. This extra stimulus to the accommodation will serve a good purpose in evoking extra stimulus to the conver- gence, the thing most needed in latent divergence. For the same reason we encounter the accommodative variety of exophoria in M + Am, The explanation is found in the incom- plete or altogether neglected use of the accommodation. The myopic eye has a far point inside of infinity, its distance from the eye depending upon the diopters of myopia. Thus in M. of 3 diopters the far point is 13". This is a convenient distance for reading and no accommodation is required. In M. of 5 diopters, the far point is 8'', which is too near for the exercise of accommo- dation. In such cases, therefore, convergence is deprived of the usual associated stimulus of the ciliary muscle, and gradually weakens. It can be readily seen, therefore, that in the presence of myopia the correction of the refraction is a necessary part of the treatment of the muscular anomaly. Indeed, when the myopia is not too high or the patient too old, it is often the only treatment demanded. The correction, in order to be effective, should be worn constantly. If, after two months' use of proper correcting glasses muscular equilibrium is not restored or the symptoms persist, medicinal treatment may be resorted to. 3. Nerve Tonics. — The remedy that has been most warmly 134 FUNCTIONAL ANOMALIES. endorsed and that the authors ha\'e found extremely serviceable is tincture of nux vomica in ascending doses. Strychnin, the alkaloid of nux vomica, is for some reason less eflficient. The beginning dose of the tincture should be 20 drops thrice daily, increasing the dose one drop every day until 50 to 60 drops thrice daily are taken or until symptoms of physiologic action of the drug appear. Then the dose is similarly decreased day by day until the original dose is reached, vv^hen the drug may be with- dravi^n. The measure that is of most service in connection with the use of nux vomica is training of the convergence faculty by means of prisms. 4. Convergence Training. — This may be of various kinds. We resort mainly to tv^^o methods. First, converging exercises with a pencil point held at arms length; this is carried in toward the root of the nose until the patient sees double when the eyes are closed and the pencil carried back to arms length and the move- ment repeated up to ten to twenty times. Such an exercise period should be gone through two or three times a day. In this way the convergence near point can be brought nearer and nearer and the positive range of convergence much increased. The same exercise to the right and left is sometimes helpful. The range and power of convergence can be distinctly increased by regular prism exercise. Prisms, bases out, have been used in various ways by different workers for many years for the exercise of the adduction; Risley, Michel, Savage, Noyes, Gould and others. (Acknowledgement is gratefully made by the senior author to his friend and preceptor. Dr. Wm. Thomson, until lately Emeritus Professor of Ophthalmology in the Jefferson Medical College, for instruction nearly thirty years ago in his ofifice, in the use of prisms both as a method of stimulating the innervational force of the external ocular muscles and as a means of relief in muscular asthenopia). The battery of Noyes or Gould is a convenient arrangement of prisms and can be employed with benefit, although the costliness of such apparatus limits its use to the consulting room. For home use the prisms are to be mounted either in an ordinary spectacle frame or in one of the numerous frames EXOPHORLA. 135 specially devised for carrying square prisms so that they may be increased ad libitum. (See Fig. 53a). The patient is given a pair of 5 degree prisms in the frame, with which he walks toward a candle flame placed at the opposite side of the room. The prisms arc not looked through as he goes toward the light, but are raised. As soon as he approaches within 2 feet of the light the prisms are dropped before the eyes and he backs away from the light gazing steadily at it all the time. Should the light appear double any time while he is backing across the room, the patient immediately raises the prisms, walks toward the light again and backs away with the prisms before the eyes until he Fig. 53a. — Training prisms for exophoria. can go the whole length of the room without seeing the candle double. This is done from ten to fifteen times two or three times a day. After two weeks 10 degree prisms are ordered to be used in the same way and after another fortnight 15 degree or 20 degree prisms according as the patient learns rapidly or slowly the trick of dissociating his accommodation and convergence. There is a class of patients for whom convergence training as above described is particularly indicated; namely, the exophorics who present but i or 2 degrees of deviation for infinity with anywhere from 10 to 15 degrees of deviation at the reading distance (prism divergence being normal). These patients respond finely to convergence training as a rule. It will often require the strictest injunctions on the part of the surgeon to impress upon the patient the necessity for, and the importance of these calisthenics, and to bring him to realize that the partial or complete relief of his asthenopia is largely in his own hands. The cooperation of the patient once secured, the prisms can be rapidly increased in strength and the fusion force often carried to 100 degrees of prism inside of eight or twelve weeks, in which event the patient is 136 FUNCTIONAL ANOM.'\LIES. pretty sure to have experienced marked relief from the asthenopia. The main difliculty in this method lies in the persistence necessary to convince the patient that little is to be hoped for without the heartiest cooperation. Many cases of severe muscular asthenopia can be made quite comfortable by the combined action of increasing doses of nux vomica and prism exercise; indeed, their value has been universally acknowledged. An interesting clinical fact in connection with this method of treatment is that if a patient start with an exophoria of 10 de- grees for distance and 18 degrees for 15 inches, (the occupation distance), the asthenopic symptoms may be entirely dissipated by nux vomica and prism exercise for two or three months, not- withstanding which the exophoria for distance will remain at 10 degrees, while that for near may have fallen to 3 degrees or 5 degrees, or have entirely disappeared; all of which goes to show that exercise of the adduction may increase the range of conver- gence (as can be found by prism tests of the adduction and abduc- tion), but will seldom influence to any extent the muscle-balance for 20 feet. In other words, we have simply made easy to the patient a much-needed coordination, and have perhaps at the same time trained the cortical fusion centers to a higher degree of efficiency. These measures are peculiarly useful in individuals who have passed through a debilitating illness, such as typhoid fever, la grippe, measles or diphtheria; also in young and growing subjects, and their action is always enhanced by life in the open air, general muscular exercise and nutritious diet. Occasional cases will be met with whose symptoms are decidedly aggravated by prism training. This is frequently a clinical indication for the use of prisms permanently in the position of rest in the patient's glasses. 5. Prism Correction. — When the symptoms of exophoria are not relieved by the preceding measures and are of such a severity that relief can be obtained only by relaxation (or easing) of con- vergence, the wearing of prisms in the position of rest is to be con- sidered (Fig. 54). The use of prisms, bases in, to be incorporated in the patient's distance correction has been deprecated by many EXOPHORIA. 137 authorities who contend that exophoria for iniinity increases under the constant wear of such prisms; furthermore, that they do not cure the deviation, but only relieve the symptoms. That this is true within certain limits must be admitted; and yet when correction of the ametropia has failed to relieve, and attempts at training the convergence have been poorly borne the trial of prisms bases in in an extra or hook front experimentally seems justifiable. In properly selected cases it will be found that when convergence has been made somewhat easier for the patient by the use of rest prisms, the convergence may then be trained to a very considerable point and the exophoria for infinity thus kept from increasing. This was our experience in seventeen out of forty-two cases in which prisms bases in were ordered for constant use. If the exophoria is the result of a temporary loss of convergence from overuse of the eyes or exhaustion of the nervous system the prisms not only give comfort, but they may gradually be reduced in strength and finally discarded. While the prisms are worn the visual axes diverge and the globes assume that position in the orbit most restful for them. The effort of convergence is partially in abeyance and the strain of opposing the power of divergence is relaxed. The eyeballs are diverged and single vision is maintained by the prisms. For these reasons it is good practice to allow a goodly proportion of the exophoria to remain uncorrected by prescribing prisms that permit constant but limited use of con- vergence. Thus, in exophoria of 8 degrees for infinity, prisms of I to 2 degrees before each eye may be tried. It is well to feel one's way with prisms, the purpose in view being not to supplant convergence, but simply to ease it up. Whether the prisms should Fig. 54. — Effect of converging prisms in exophoria. 138 FUNCTIONAL ANOMALIES. or should not be worn constantly depends upon the symptoms accompanying the use of the eyes for distance. Defects of 4 degrees and less for 20 feet rarely require their use. Higher defects will usually demand their constant use. There is a limit, however, to the benefit to be derived from prismatic correction according to sex, age, occupation, etc., but in general terms the highest degree of prism that can be comfortably worn may be placed at 5 degrees before each eye. 6. Prism Correction for the Reading Distance. — In certain cases of exophoria it is at times sufficient to employ prisms in connec- tion with the reading or occupation glasses only. This is espe- cially true in presbyopic exophorics. The influence of age in unmasking or perhaps even developing exophoria is unmistak- able. Reference to the accompanying table TABLE E. Decade. . / , Decade. . .' , times found. times found. Under lo 6 41 to 5c 124 1 1 to 20 34 5 1 to 60 59 211030 go 611070 14 31 to 40 106 Over 70 6 setting forth an analysis of the incidence of exophoria in the various decades of life will show that the decade from forty to fifty presents the greatest number of cases of exophoria. Less than I /lo of all the cases occurred prior to the 20th year of life and over one-half of all the cases in the period between thirty and fifty years of age. It is not at all uncommon to find presbyopes who reveal but i to 2 degrees of exophoria for infinity with 8 to 12 degrees for the reading distance. Prism training often pro- duces the happiest results in such patients, but when it fails one need not hesitate to incorporate a i to 2 degree prism base in in each lens (preferably i degree) and the effect is generally most gratifying. Decentration of the lenses will accomplish the same result, but more will be said of this in another place. When all the procedures mentioned fail to afford relief we are obliged to consider operation. EXOPHORLA.. 139 7. Operation. — The surgeon has the choice between tenotomy of the externi on the one hand and advancement (with or without resection) of the interni, or of the capsule, on the other hand. If exophoria depends upon lessened convergence power, there would seem to be no alternative between these two procedures; that the choice must fall upon measures that will strengthen con- vergence rather than weaken divergence. In our own practice tenotomy of the externi for exophoria is not often resorted to. Advancement is performed in nearly every instance. We believe this is correct practice founded upon sound physiologic principles, yet we are obliged to admit in all fairness that our results have not always been as satisfactory as we or our patients could wish. Advancement (capsular or capsulomuscular) is far more difficult and tedious to perform than tenotomy, more painful and incapaci- tating to the patient and it may not increase the power of con- vergence. When accurately done we believe it is superior to and gives more lasting results than tenotomy. On the other hand, tenotomy can be done under local anesthesia; it is extremely simple and easy to perform, it can be made most accurate, it inflicts but little pain, and a very short period of incapacity and when divergence is greatly in excess occasionally affords brilliant results. In patients under thirty years of age it would generally be best to resort to advancements; after that time, when the divergent forces are more in evidence, tenotomy may be considered when divergence can be plainly shown to be greatly in excess of normal. In deciding as to operative treatment, the etiologic relation between exophoria and hyperphoria must be constantly borne in mind. (See chapter on \'ertical Imbalance and Lateral Imbalance) . Whether one or both eyes shall be operated upon is to be decided on the merits of each case. The effect in degrees gained by a single operation depends largely on the preserved power of ad- duction. As a rule, it does not exceed 5 to 6 degrees and when more than this amount of correction is demanded, as is the case in most subjects for operation, each internus should be advanced. It is true that more effect in the divergence can be obtained by full tenotomy of the externi and at first sight this operation would I40 FUNCTIONAL ANOMALIES. appear to be indicated, but full tenotomy of one or both externi should never be done because of the serious objection of dimin- ished external rotation. Moreover, as has been said, there is not so much promise of permanency of result and increase in adduction with tenotomy as with advancement. So that if the surgeon is sufficiently sure of his technique, he will probably obtain the best results by operating on both interni, dividing the amount of correction between the two eyes (as nearly as may be), at the same sitting. Postponement of the second operation is not contra-indicated, yet the preference should be given to the double operation since by this plan the dread and anxiety of the patient are reduced more than one-half and the eyes are in a condition to respond equally to the innervational impulse. If these facts are explained to the patient it is improbable that he will raise objections to the plan proposed, but will submit philosophically to the reasoning of the surgeon. (For description of tenotomy and advancement see chapter on Operations.) HYPERPHORIA Hyperphoria is that condition in which there is a tendency of one visual line in a direction above that of the other. Hyper- phoria (latent vertical squint) differs from hypertropia (manifest vertical squint) only in that single vision is not possible in the lat- ter condition, and the eye that is more ametropic, or is at the greater muscular disadvantage, gives up the struggle and actually deviates upward or downward. If we accept the above definition, it will be found that hyper- phoria is by no means rare, nor is its presence inconsistent, in some cases, with perfect health and comfort in using the eyes, in which event there can be no excuse for treatment of the tendency to deviation. An analysis of the findings at the first visit in 700 consecutive refraction cases occurring in our practice showed that 20 per cent, of all of them revealed hyperphoria of one-half degree or more; and a recent study of 3600 refraction cases in our private practice in- dicates 7 per cent, in whom prolonged study of the case revealed i degree or more of hyperphoria. Carpenter found it in 35 per cent, of his private cases at the first consultation, Posey in 13 per cent., Bannister (working among the U. S. Navy recruits) in 7 per cent., and Howe and Williams in 16 per cent. This would indicate that about one in ten of all patients who are the subjects of muscular or accommodative asthenopia will during the preliminary exam- ination display some degree of vertical imbalance, either alone or associated with esophoria or exophoria. It should ever be borne in mind, however, that hyperphoria (like esophoria or exophoria) occurs in a fair percentage of individuals in whom careful re- fraction alone without any special optical treatment of the muscle status seems to give perfect relief. Some people carry a vertical error of i to 2 degrees all through a life of high tension and large usefulness without any particular discomfort, while in 141 142 FUNCTIONAL ANOMALIES. Others one-half to three-quarters of a degree is sufficient to make life a burden. Nature is marvelously elastic in her adjustments. So that the mere finding that a patient has hyperphoria is of itself nothing until the vertical deviation is viewed in its relation to his or her heredity, environment, temperament, occupation, physical condition and last, but most important, the refractive status of the eyes. Hyperphoria of 3 degrees in a soldier may easily prove a negligible quantity; while hyperphoria of one to one and a half degrees in a student, accountant, stenographer, private secretary, etc., may alter their whole career. One must be on the lookout always for spurious hyperphoria. The follow- ing case is in point : A. W., female, aged sixteen. Comes on account of difficulty in all near work. General health fair. Vision R. E. 5/7; L. E. 5/9. Accommodation normal. Muscle status esophoria 4 de- grees, left hyperphoria 2 degrees. Under atropia the refraction status was R. +0.50 sph= + 1.25 cyl. 75 degrees L. +0.62 sph= +1.00 cyl. 135 degrees after two weeks use of the cylinders only, the hyperphoria dis- appeared nor was there any in evidence i year later when the case was studied again. Such cases are not rare. This class of cases (ametropic), along with those secondary to gout, rheumatism, central nervous lesions and other general diseases, comprise what are known as temporary hyperphorias in contradistinction to true or permanent hyperphorias which occur independently of constitutional conditions, and persist after long use of the closest correcting lenses. Symptoms. — The symptoms of hyperphoria are ocular and re- flex. The ocular symptoms are: 1. Chronic hyperemia of the lids, often giving rise to a condition aptly likened by one writer to the "hot eye" of gout. 2. Epiphora, generally unilateral and seemingly without nasal or ocular cause. 3. Defective Vision. — It is not unusual to find vision of but HYPERPHORIA. 1 43 2 JT, to I J2 in an hyperphoric eye even after accurate correction of a low-grade ametropia; indeed, it may be impossible to give each eye better vision than 5/7, a fact easy of explanation, how- ever, if it is borne in mind that an actual vertical imbalance of I degree will result in a separation of images at 20 inches of 6 i /2 mm. Such a patient, if a worker at the occupation distance, will most surely be troubled from time to time, 4. Confusion of images, which is the result of the transient diplopia. It may be urged that many students carry a hyper- phoria of I degree or more through a busy career extending over many years without experiencing any annoying symptoms whatever. Such persons either possess a physical and nervous system that would weather any storm, or they have, consciously or unconsciously, learned, by carrying the head toward one or the other shoulder, to neutralize their hyperphoria wholly or in part. This habit constitutes the fifth important symptom of true hy- perphoria, namely: 5. Carriage of the Head. — The head is usually tilted toward the shoulder opposite to the hyperphoric eye, a statement that may sound strange, but when it is remembered that in right hyperphoria the image is really seen lower by the right eye, it naturally follows that the head must be tilted toward the left shoulder if the images are to be brought to a level and binocular vision thus rendered an unconscious act. Graefe referred to the turning of the face to one side in " insutificiency of the interni" to aid the weak adductors, but he said nothing of the peculiar carriage of the head in hyper- phoria, which is equally common, 6. A peculiar facial expression will often be noticed, especially when an hyperphoric is in animated conversation; several furrows will ridge themselves above one eyebrow, and even the eyebrow itself may be raised above the level of its fellow from 4 to 10 mm., giving a quizzical expression to the face. There should also be mentioned, in this connection, the wide open eye, or stare, seen in many hyperphorics. Occasionally an apparent ptosis of many years' duration is dispelled by prismatic or operative correction of hyperphoria. 144 FUNCTIONAL ANOMALIES. Not less important, as immediate symptoms of vertical deviation tendencies, are the painful eyes, photophobia and drowsiness induced by any long-continued near work, notwithstanding that the patient is wearing proper lenses. The reflex symptoms of hyperphoria include more or less con- stant headaches, amounting sometimes to a migraine, nausea, vomiting, dizziness, and vertigo. In some instances the latter is so marked as to cause momentary unconsciousness and a symptom- complex that has more than once led to a diagnosis of epilepsy or even cerebral tumor. We believe it is the latter class of cases that are vaunted by many as instances of essential epilepsy par- tially or even entirely curable by eye-treatment alone. The headaches of hyperphorics are almost invariably aggra- vated by near work; also by moving in a crowd or watching rapidly- moving objects (panorama headache of Bennett). Other hyperphorics will escape the headaches, but present, instead, frequently recurring nausea, vomiting and vertigo, the latter especially brought on by any continued looking up or down. Etiology. — Intrinsic hyperphoria is commonly due to over- action on the part of one muscle (hyperkinesis) or underaction on the part of another (hypokinesis). It may also result from ano- malies in the formation and relative position of the orbits or from peculiarities in the attachment, development, insertion or action of one or more muscles. Age is now by general consent admitted as one of the factors in the unveiling if not in the production of hyperphoria. In a series of cases reported by one of us in 1900, one-third were under thirty years of age and two-thirds over that age. (Compare with the same facts in exophoria). We have found intrinsic hyperphoria in a child of twelve, but this is unusual. There is no satisfactory explanation for the increase or perhaps unmasking of a latent hyperphoria. The ' parallel process of uncovering of latent hypermetropia by advancing years naturally suggests itself and may have much to do with this seeming actual increase in hyperphoria. Congenital paresis of one of the ele- vators or depressors — usually the superior recti, is a not infrequent cause of hyperphoria (or hypo-phorisL) as will be alluded to later on. HYPERPHORIA. 145 Diagnosis. — The assertion that hyperphoria exists in a given case ought not to be based on any one test, but demands corrob- oration by every test at our command. No problem in ophthal- mology calls for greater accuracy and adjustment of instruments and close observation. When we say hyperphoria we use a clinically convenient term. We have not told whether one visual axis is abnormally high or the other abnormally low nor have we Fig. 55.^Reimold's optometer. implicated any particular one of the elevators or depressors. So that after we have established the diagnosis of hyperphoria (or simply a deviation of one visual axis above or below the other) we should endeavor to discover if possible whether one axis has a tendency to become abnormally high or the other abnormally low. In conducting many of the tests, Risley's, Reimold's or some similar combination of the optometer and phorometer (Fig. 55) gives satisfactory results. 146 FUNCTIONAL ANOMALIES. Maddox Rod Test. — When the patient's face has been brought close up against the back surface of the optometer, and the latter been found to be absolutely level by means of the plummet or spirit level attached for the purpose, the compound Maddox rod is slipped into one of the cells, say the right one, and so turned that the streak of light is exactly horizontal. If the streak passes above the flame, there is shown either right A^'/Jophoria (downward tendency of right eye), or left hypei"^hor\di (upward tendency of left eye). If the streak be found below the flame there is right M'^erphoria (upward tendency of the right eye) or left M'/>ophoria (downward tendency of the left eye). The same facts hold good when the Maddox rod is placed before the left eye, so that the test can be applied by placing the rod before either eye. The prism that carries the streak into the flame is the measure in degrees of the hyperphoria. Some prefer to use the phorometer, but the Maddox rod has an added advantage in that if the hyperphoria appears to be of a different amount according as the Maddox rod is placed before one or the other eye, we thus learn that there must be a slight paresis of one of the elevators or depressors; that when the paretic eye fixes, the separation of the light and the streak will be greater (answering to the secondary deviation) than when the sound eye fixes. On the other hand, in some individuals the impulse to bin- ocular vision is so overpowering a thing that they will frequently fuse the light and the streak, thus covering up their muscular error; but if the rod is quickly reversed several times in the trial frame from the vertical to the horizontal position one is much likelier to break up the strong fusion impulse in such a case and get at the true deviation. Diplopia Tests. — If the phorometer be used, the prism or prisms with which diplopia is effected are already in position, and if one image be higher than the other, all that remains to be done is to rotate the prisms by means of the small lever until the images are level, when the resultant right or left hyperphoria will be indicated by the pointer on the arc graduated in degrees on the front of the phorometer, and can be readily read off. HYPERPHORIA. I47 Parallax Test. — Seal the patient 20 feet or farther from some small object that is situated directly in front of and on a level with the eyes. The object (a small luminous point of light in the middle of a large black area, for instance) must be so placed that it will not be projected upon any surface back of it. Note carefully that the patient's head is not tilted to one side, then carrying some sort of cover to and fro several times from one eye to the other, the patient is requested to watch closely whether the object as seen by one eye appears any higher than the other. If so, vertical imbalance is present and its degree is to be determined by the prism that will make the object appear on the same level with each eye. It will sometimes be necessary to carry the cover from one eye to the other fifteen to twenty times before any difference in level in the apparent position of the object becomes noticeable, but by this means the lower degrees of hyperphoria are frequently unmasked. The parallax test, when thoroughly understood, is susceptible of great delicacy of application and by it 1 1 2 degree of hyperphoria is easily detected. Duane, whom we must thank for the test, claims that he thus estimates even i /4 degree of hyperphoria. If the patient be ametropic, he must wear his correction during all the tests. Thus far we have determined only that one ocular axis has a tendency to deviate above, or the other below the axis of the fellow^ eye. We have not located the defect nor decided whether it be due to overaction of the muscles of one eye, or underaction of the corresponding muscles of the other eye. Resort must now be had to prisms, to learn the prism power of upward and downward rotation. This will be found to fluctuate from 2 to 3 degrees, but the fact of prime importance is that whatever the power of prism rotation, supraduction and infraduc- tion should be equal. If the eyes can overcome a 3 degree prism, base down, they should likewise overcome a 3 degree prism, base up. A difference of i degree or more between the supraduction and infraduction of the same side indicates the probable existence of hyperphoria; moreover, a supraduction exceeding 3 degrees 148 FUNCTIONAL ANOMALIES. (except in moderate and high myopia) is always suspicious and presumptive of hyperphoria. If there be suspicion of hyperphoria and the supraduction and infraduction as found by prisms prove equal, it becomes necessary to map out the field of monocular fixation, especially the upward and downward limits. This is done by having the patient follow with the eye (but not with the head) a very small test-object, such as a black dot on a white card, which is carried as far up and as far down the arc of the perimeter as the eye will follow it without wavering or receiving a blurred image of the object. The arc through which the eye has rotated may be measured by the peri- meter, the head resting on the chin-support and the fellow eye excluded as in ordinary perimetry. This examination should show at least 35 degrees to ^8 degrees of upward, and from 50 to 55 degrees of downward rotation. For the precise measurement of these rotations, Stevens employs his tropometer (described above), and if upward rotation falls short of, or exceeds, 32 degrees, or if downward rotation exceeds or falls short of 55 degrees, the corresponding elevators or depressors are to be viewed as causative in the hyperphoria. If upward rotation is excessive, the hyperphoria is likely due to overaction on the part of the elevators of the hyperphoric eye. If downward rotation be excessive, the hypophoria is likewise due to excessive action (hy- perkinesis) of the depressors of the hypophoric eye. If upward or downward rotation be insufficient (hypokinesis), the deviation is probably due to weakness, or even paresis of one or more of the vertical muscles, in which case diplopia can be readily elicited when the eyes (but not the head) are turned 20 degrees or more from the primary position, the diplopia increasing as the test- object is carried in the direction of the weak muscles. Much information may sometimes be gained by search of the extreme upper periphery of the binocular fixation fields with a one candle electric light in a darkened room, a red or cobalt glass placed before one eye, to learn whether there is paresis of any of the elevators and similarly in the extreme lower field for paresis of any of the depressors. Hyperphoria and hypophoria HYPERPHORIA. I49 may be thus at times differentiated. For instance: V. M. M., female, married, twenty-three, referred by her physician on account of panorama headache, also train and trolley nausea and vertigo, so marked that she could not ride more than eight to ten blocks in the trolley cars. Use of her eyes for reading and sewing was limited to fifteen to twenty minutes, and this in spite of the fact that she was wearing a good correction. She was a tall, thin, poorly nourished girl, hyperesthetic and on the verge of neurasthenia. Both eyes were normal anteriorly and with her correction, which was: R. +50+1.00 cyl. 100 degrees L. +75 + 0.90 cyl. 80 degrees vision was full and sharp 5/4 in each eye. The eye grounds showed the irritation and low grade congestion so often found with such muscular anomalies. Her muscle status was exophoria of 2 degrees for infinity and 5 degrees for the occupation distance. There was right hyperphoria of 8 degrees for infinity (when the eyes were in the primary position) and 9 degrees at the occupation distance. Search for diplopia in the extreme upper periphery of the binocular fixation field revealed vertical diplopia with the left image higher in the middle and left upper field, most marked in the left upper field where the separation of the images was about 4 inches. Paresis of the left superior rectus was thus plainly shown. On questioning her I learned that for years she had occasionally seen double when she looked at anything far up to the left, but thought nothing of it. So that the apparent diagnosis of right hyperphoria in the case immediately gave way to the proper one of paretic left hypophoria. It may be stated, in passing, that a 4 degree prism base up was incorporated in her left glass and after two years use of it she can ride 25 miles in a trolley car without the slightest ocular disturbance, she has lost all her headaches and hyperesthesia, and can use her eyes for one and one-half to two hours at near work comfortably. Finally, when the tests for hyperphoria at 20 or more feet are concluded, search should be made for vertical imbalance at 15 to 150 FUNCTIONAL ANOMALIES. 20 inches. In this test Graefe's dot and line may be used or the dot only. Better yet is the small one candle electric light (suggested for the similar test in exophoria) to be held at 13 to 15 inches. Any vertical imbalance will then be recognized the moment the Maddox rod is placed before either eye and the amount readily measured. The patient should, of course, wear the proper correction (accurately centered) during this test and if presbyopic should wear that correction. It will frequently be found that hyperphoria for 15 inches is a trifle more than for distance. The Relation Between Hyperphoria and Lateral Deviation Tendencies. — It has been claimed that many cases of esophoria and exophoria are directly dependent upon and caused by a tendency to upward deviation of one of the visual axes, and no doubt there is much truth in this claim. It is easy to conceive that when vertical tension is out of equilibrium the lateral muscles in their efforts to fuse images will tend to turn the eyes now in and now out, or will acquire a habit of forcing the lateral tendency in one or the other direction. This dependence has been illustrated by comparing the lateral muscles, in their efforts to fix, with the lifting of a log with a pair of tongs, the clamps of which are not in a horizontal line. Many cases have been reported where not only deviation tendencies, but actual lateral turnings have been cured by restoration of vertical equilibrium, and in the con- sideration of causes which lead to exophoria or esophoria, vertical tensions should be given a prominent place. Theoretically, all cases of uncorrected hyperopia ought to have upward and inward tendencies on account of the resultant action of all the external muscles supplied by the 3rd nerve, and the reverse will hold in exophoria, namely: a tendency down and out. This interde- pendence can be well shown when the grade of the defect is high enough to allow of diplopia with the cobalt glass test. It will be found by this test that there are few cases of lateral turnings that are not complicated with vertical turnings, and it will also be found that hyperphoria frequently changes from one eye to the other, according to the eve used in fixation. If the right eve should HYPERPHORIA. 151 fix and the left, armed with the cobalt glass, sees the false image to the left and below, we have hyperesophoria (really hypereso/ro/>fa while the cobalt glass is before the eye), and if the glass is trans- ferred to the other eye, that eye now sees the false image and we have R. hyperesophoria. In other words, the cobalt glass deter- mines the fixing, and hence, also, the squinting eye. The reason for the association of hyperphoria with esophoria in hyperopia has already been explained, and an analogous explanation fits the association of hyperphoria with exophoria. If we admit that the tendency outward is a passive anomaly and due to a loss of converg/snce, this deficiency of innervation affects not only lateral but also vertical tensions, and where we should have in esophoria hyperphoria, we should expect to find in exophoria hypophoria. Therefore, in considering the treatment of exophoria or esopho- ria, the condition of the vertical tensions must be thoroughly investigated and their causative relations determined where possible. The question often is raised, does the lateral imbalance depend upon the hyperphoria, or is the reverse true ? The answer to this question depends upon the relative rotational powers of the vertical and lateral muscles. If the abductors and adductors show normal rotations (as determined by means of prisms and the tropometer) the elevators or depressors are likely at fault. If these latter exhibit normal and proportionate dynamic conditions, the lateral muscles are probably causative; for instance, Mr. L., aged thirty-one, a minister of the gospel and a close student, exhibits with the Maddox rod at 20 feet, exophoria of i degree and R. hy- perphoria of I degree. At 20 inches the Maddox rod showed exophoria 12 degrees. Were now the lateral or vertical muscles at fault ? Estimation of the prism power of rotation with rotary prisms showed : Abd. = 6 degrees; add. = 18 degrees; R. Supra ==3 degrees; R. Infra =1 degree. The lateral muscles were there- fore proportionate in their tensions and the difference of 2 degrees in the right supra- and infraduction was sufficient to fix the vertical muscles as the offending ones; in this particular case the fault consisted in either overaction of the elevators of the right eye or the depressors of the left eye — or underaction of the depres- 152 FUNCTIONAL ANOMALIES. sors of the right eye or elevators of the left eye. This last point of overaction or underaction is to be determined by the tropometer. Treatment. — The treatment of hyperphoria resolves itself into four phases. 1. Exclusion of any general disease or affection of the central nervous system, incipient tabes and general paresis in particular. For instance: M. A., aged thirty-four, broker, referred by his family physician on account of eye symptoms, showed 4 degrees of left hyperphoria. No diplopia could be shown in any part of the binocular fixation field. There was no other abnormality about the eyes save incipient Argyll-Robertson pupils, which led to the suggestion that he consult a neurologist. One year later without the use of any correcting glasses (as he was practically emmetropic) the hyperphoria had disappeared entirely, but the Argyll-Robertson phenomenon was completely developed, and his accommodation was normal. Obviously it would have been bad practice to resort to either prisms or operation in such a case. 2. Thorough-going refraction just as in esophoria and exophoria, the correction being done under cycloplegia up to forty-five years of age. The persistent use of such corrections will suffice in many cases if not to partially or entirely dispel the hyperphoria, at least to render the patient so comfortable that treatment of the vertical imbalance as such need not be considered. We have already recited such a case history. It must be admitted, however, that correction of the refraction does not of itself so often prove the only necessary factor as it does in esophoria and exophoria. In our experience, esophorics profit most by a good correction alone, exophorics not so often, and hyperphorics least often. 3. If, after faithful use of a good correction and careful atten- tion to life habits, the hyperphoria persists and is annoying, it is well to try the effect of a prism or prisms that correct about 1/3, of the hyperphoria. A convenient method is to have the prisms slipped into what is known as an extra-front, to be hooked over the regular glasses (Fig. 56). The prism effect may be divided between the two eyes {base doimi before one, base up before the other), or the whole prism to be used HYPERPHORIA. 1 53 may be placed base down before the hyperphoria eye, preferably the former for reasons to be stated later. By this means prompt and at times surprising relief is sometimes obtained, as, for instance, in the following case: F. E., aged twenty, a goldsmith, works all day at a distance of from 8 to lo inches soldering small gold trinkets. Given eighteen months ago by a colleague (who used a cycloplegic) R. E. + .50 D+.50 Cyl 90 degrees L. E. + 0.75 ^^'^• With this correction he was much more comfortable at his work for two or three months, but his eyes and head began to trouble again, when his oculist, after much pains, ordered a i /2 degree prism, Fig. 56. — Hook or extra front. base down, to be incorporated in the left glass, indicating that he found left hyperphoria. (This point is emphasized because of the subsequent developments in the case). Again he pursued his work with renewed comfort for about three months, when the old train of eye and head symptoms once more took up its march. At this time he came under our observation, and on September 14, 1897, he was carefully refracted under thorough cycloplegia and the findings of the previous worker were confirmed in all but the muscular details. September 16, 1897. Maddox rod shows esophoria i /2 degree. No hyperphoria. Abduction =7 degrees. Adduction =15 degrees. Left supra- and infraduction = 3 degrees. September 30, 1897. Maddox rod used over patient's correc- tion shows exophoria i degree. Right hyperphoria i /2 degree. {Left hyperphoria had been found by his former adviser). With the parallax test R. hyperphoria i 1/2 degrees. Exophoria 2 degrees. October 14, 1897. Left hyperphoria i degree full, with parallax 154 FUNCTIONAL ANOMALIES. test. Maddox rod shows vertical balance. Control tests made four times during the succeeding month showed R. hyper- phoria I degree full with the parallax test, and each time R. supraduction equalled 41/2 degrees, while R. infraduction equalled 21/2 degrees. This accord in results in four consecutive examinations justified having the i /2 degree prism, base down, taken out of the correction of his left eye and having him try a 3 /4 degree prism, base down, before the right eye in a slip front to be hooked on over his glasses while at work. One month later he stated that he had never been so comfortable. He was then directed to have the 3/4 degree prism, base down, incorporated into his right glass, because he was so much annoyed by the reflections from the prism in the extra front. Four months later the patient stated that he was working at his soldering bench (at a distance of 8 inches) for 10 hours a day, without discomfort of eyes or head. This case illustrates how the most careful worker may be led into error by a spastic hyperphoria which we believe this young man to have shown in the earlier part of his trouble. Later, long-continued observation of his case and prism estimation of the upward and downward rotation showed not only right hyper- phoria, but the difference between the right supraduction (4 i /2 degrees) and infraduction (2 i J2 degrees) pointed to the overact- ing elevators of the right eye. as the cause of the deviation. Theo- retically, tenotomy of the right superior rectus or of the corre- sponding inferior oblique was indicated, but prisms in the position of rest (favoring the underacting or weaker depressors of the right eye) gave the patient such prompt and lasting relief that operative measures were not to be thought of. Naturally there are those who contend that the prism is but a crutch that must needs be added to from time to time to the great disadvantage of the patient's ocular muscles, but as there is almost no other alternative but operation, prisms must be considered and must be offered to the patient as a possible means of relief. Also there are those who claim that if in a given case 2 degrees of hyperphoria are definitely shown, that a 2 degree prism should be HYPERPHORIA. 1 55 incorporated in the patient's lenses to establish vertical balance once and for all. From the academic standpoint this would seem* to be perfectly reasonable, but abundant experience has shown that the average patient glides much more easily into the com- fortable use of vertical prisms if one-third to one-half of the devia- tion for distance is employed, having the patient to understand that as time goes on more prism strength may be demanded by the eyes. Latent hyperphoria is ofttimes uncovered by the latter process and there is every reason to believe that once a patient's full hyperphoria has been learned by this method there is little likeli- hood that any more deviation will reveal itself no matter how long the case is studied. We have a long series of cases in support of this belief. Yet warmly as we wish to endorse the practice of temporary trial of prisms in the hook front, there are many individuals whose symptoms are only aggravated by this measure, in which case exercise of the vertical muscles may be tried -by means of prisms placed base up or down, as the case requires. Savage believes this method to be of value in deviation ten- dencies under i 1/2 degrees, and says: "The prisms used should range from 1/4 to 2 degrees; most cases will not require stronger than a i degree prism. The apex of the prism should be placed in the direction of action of the muscles to be developed, the patient exercising from two to ten minutes, two to five times daily. The object looked at must be 20 feet distant, and it should be seen through the prism 5 seconds, and then without the prism 5 seconds, and so on throughout the sitting." While our own experience with this method in hyperphoria has been limited, our results have not been such as to lead us to expect much relief from this kind of training. If, then, a patient presents persistent hyperphoria and will tolerate neither prisms in position of rest nor exercise of the weaker muscles, are we to turn immediately to operation as a last resort ? Not so. Many factors must be determined before operative treatment is applicable. For instance, it is not to be thought of when the hyperphoria is recent, progressive, or variable; in case of 156 FUNCTIONAL ANOMALIES. central nervous disease, in rheumatic, gouty or diabetic subjects, or in those who have not enjoyed binocular vision for years (strictly speaking, these are instances of hyperlropia). Moreover, when hyperphoria complicates esophoria or exophoria, it is not infrequent for the vertical anomalies to right themselves, or at any rate for the symptoms attributed to them to disappear when the lateral muscles have been well trained with prism gymnastics. Particularly is this true when exophoria coexists. 4. Operation. — Hence we find operative treatment of the hyper- phorias narrowed down to the permanent, constant or static variety, where the deviation tendency is constant in amount and character notwithstanding at least six months of the proper cor- rection, where all tests agree in showing marked over or under- action of one set of elevators or depressors, when prisms have not been well borne, and exercises are of no avail. In the former set of cases (overaction) tenotomy is highly satisfactory and often brilliant in results, if the case has been selected in accordance with the above suggestions. The dis- sipation of reflex symptoms following upon tenotomy for hyper- phoria is sometimes little short of wonderful, and has doubtless led many witnesses of such cures into operative treatment of hyper- phorias that are distinctly outside of the operative class, and given the extreme illogical conservatives in ophthalmology occa- sion to deride the judicial and unjudicial alike as "muscle- snippers." Hyperphoria, constant in degree and kind, definitely due to underaction on the part of the vertical muscles, may be met by advancement or muscle shortening of the underacting muscle or muscles, and in properly selected cases the same results may, as a rule, be expected. It should be borne in mind, however, that ad- vancement of a vertical muscle is not so easily performed as on a lateral one and this may influence the surgeon to resort to tenotomy of the opposing muscle. Operation, whether tenotomy or advancement, should always aim to slightly under-correct the deviation, the remainder being often amenable to prism exercise of the weak muscle immediately DECENTERING LENSES. 1 57 and from twenty-four to forty-eight hours after the operation; in this way the effect of an operation that is insufficient may be considerably increased; any slight remaining deviation can be readily met by the necessary prism in the position of rest. Surgeons of large operative experience with muscular ano- malies prefer to aim at a slight over-correction of the imbalance, because, as they assert, reattachment of the operated muscle is almost sure to be attended with some loss of the original effect. The practice is a safe one, however, only in the hands of those who have perfected themselves in the technique of operations on the ocular muscles. DECENTERING LENSES. Some oculists prefer to decenter spherocylindrical lenses rather than to write for the lens and the prism separately. Especially in Great Britain is this in vogue. If this practice is to be followed it is well to bear in mind the general rule that for every centi- meter (or ID mm.) of decentering there will result as many prism degrees as there are diopters in correcting lens. Thus: + 4.00 sphere 3 4 degree prism base out may also be written 4-4.00 sphere decentered i cm. outward, (or 10 mm.). or -|- 4.00 sphere 3 2 degree prism base out may also be written + 4.00 sphere decentered 5 mm. outward. While the ophthalmologist may occasionally have recourse to this method of securing a prismatic effect we do not recommend it as a routine measure. Opticians in this country are in the habit of receiving prescriptions as follows; -f- 2.00 sphere -|- 3 ^-S^ cy'- ^^i^ 45 degrees 3 ^ degree prism base in. and they then decenter the lens to produce the proper effect. The table prepared by Dr. Edward Jackson here shown indicates the amount or decentering of a lens of known focal length to produce a given prismatic effect. 158 FUNCTIONAL ANOMALIES. O « I a Jd c o h •c p, °o C u u o s s N\Ot^00 O^ir-jO^irivnt~~O^rOP) 00 I^ rO « M M M M c e2 s •a 5d u Tj-TtTj-rororororoN m M ii M M c o t o c u Q s cjOt^oO-^Ovr^OvNt^roONvO-^M mvO^^-^ Tj- (S w w c o o i ^ s 5 c Q s a t^00vO'J^>-iO»t^iO'tP)H On t^oo 0) Or^sO u-jTtTfrororoPi P< M M w N O m c o ! =2 S •d o c u Q s s (VJMTl-Mf^I^ lOMOO^O-^P) OOOr^vOlO'* 00V}-ost^ir)' 00Ov^O'*fOrOP)!NMI-IW>-ll-ll-IHHHWM M c ! O o h s •c a, o i-i c 8 u O t-~HrOO\VOrO(S ONOOOt^I^vO^OOiOi'l"^ •■"troNWi-iHMM ■ s o i2 a o '■B d w M.PO'^w^vO t^oO CNO w N ro'^i'". ^O r^OO 0>0 TESTING PRISMATIC LENSES. '59 On Testing Prismatic Lenses. The prescriber should be prepared to test the correctness of prismatic lenses when they are returned to him for inspection. A common usage is to select some object in the room with a long straight side to it such as the door jamb. With the sphero- cylindrical clement of the lens properly neutralized the optical center of the whole combination is held before the observer's right eye and in line with the door jamb, when that portion of the Fig. 57. — Effect of a prism in breaking the edge of a door jamb or any straight line. edge of the jamb seen through the lens will appear displaced to one side. (Fig. 57). The prism that will restore the displaced portion of the door jamb so that it appears continuous will be the measure of the prism that is incorporated in the lens. This same principle has been utilized by Zeigler in designing his card for measuring the prism strength of such lenses. After the spherocylindrical portion of the lens has been properly neutral- ized as in the preceding experiment, it is held at one or two meters from the card (depending on which distance the card is i6o FUNCTIONAL ANOMALIES. adapted for) and the prism strength immediately read off accord- ing to the amount of displacement produced. It is convenient, accurate and serviceable (Fig. 58). One other method remains, the use of the douziememeter.^ The instrument is applied to first the nasal and then the tem- poral edge of the lens, both of which should measure the same 16 U 12 10 8 6 4 2 15 13 11 9 7 5 3 Fig. 58. — Ziegler's prism measure card. in case there is no prism element in the glass (Fig. 59). The same is true of the upper and lower edges of the lens. If the douziemeter registers say 10 douziemes for the nasal edge of a lens, and 6 douziemes for the temporal edge, the nasal edge being 4 douziemes thicker represents a i degree prism base in. A lens that is 2 douziemes thicker at the nasal than at the temporal edge would represent a 1/2 degree prism base in and a lens 8 * The name is derived from tiie French douzieme — or one-twelfth — having refer- ence to the old system of twelve lines to the inch. The scale of the douziemeter is marked in twelfths of an inch, or lines. TESTING PRISMATIC LENSES. l6l douziemes thicker at the nasal than at the temporal edge would represent a 2 degree prism base in. The same method of measurement holds in measuring the upper and lower edges to detect any vertical prism that may be present in a lens. Fig. 59. — The douziemeter. HETEROTROPIA, ESOTROPIA.^ Esotropia manifests itself externally by an inward deviation of one cornea, or the inclination of the visual axes toward each other, so that they cross at some point inside of infinity; or more correctly speaking, the visual axis of one eye is directed toward that of the other." Etiology. — The factors that individually or in combination produce: esotropia are : (a) Refractive errors (generally H and Ah conditions). (b) A congenitally weak fusion-faculty. (c) Congenital paresis of one or both external recti (to be dis- tinguished from true congenital abducens palsy). (d) Obstetric injuries to the eyes. Refractive Errors. — The usual refractive status in most subjects of esotropia is that of compound hypermetropic astigmatism. The error need not necessarily be high. Many esotropic chil- dren do not manifest more than 2 diopters of error. In the cases that are solely due to the refractive error the correction of the abnormal refractive status with suitable glasses generally causes the strabismus to rapidly disappear. This variety conforms absolutely to Bonder's theory as to the dependence of the deviation on the ab- normal convergence stimulus set up by the refractive error, and may properly be called accommodative esotropia. Not all cases of esotropia, however, are explainable on this basis. Ninety-six per cent, of all children are born hypermetropic and the question may justifiably be put, " Why do not all hypermetropic children show esotropia?" Some other factor must, therefore, be opera- tive and the most probable one is a Congenitally Weak Fusion Faculty. ^ Synonyms. — Internal or convergent strabismus; internal squint. 2 The student is urged to read the chapters on "The Evolution of Binocular Vision" and "The Relation between Accommodation and Convergence" before entering upon the study of esotropia. 165 l66 FUNCTIONAL ANOMALIES. There seems to be much basis for the supposition that certain children exhibit a very weak fusion faculty. Whether this is due to hereditary influence or to imperfect devel- opment of the entire visual apparatus during foetal life is still a mooted question. Nevertheless, the fact remains that a goodly percentage of esotropic children are the subjects of this weakness, in consequence of which the child's eyes do not acquire normal conditions and sooner or later begin to exhibit abnormal devia- tion (generally in the direction of convergence). It will be readily seen, therefore, that in this variety of cases it matters little whether the refractive condition is hypermetropic, emmetropic, or myopic, the deviation develops quite the same; as for instance in the following case: H. G., aged three, brought because of an esotropia that had begun to appear about a year previously. The little patient was a fine, lusty, healthy boy, whose personal and family history were good and whose eyes seemed to be normal in every respect save for the deviation, which equalled 40 degrees. Under thorough atropinization the eye -grounds were found normal, and the retino- scope showed only one-half a diopter of hypermetropia without any astigmatism. In the presence of so insignificant a refractive error some other factor had to be sought for and it was found that his fusion faculty was practically absent. Obviously the treatment had to be carried out without the help of any correcting glasses. Or esotropia may be found in a child with myopia, as follows : W. S., aged four, a strong, healthy child began to show occa- sional deviation of either eye near the end of his second year. There was no illness, no trauma; in fact, no contributing factor of any kind that could be made out. He had three sisters, all of whom presented normal eyes. His deviation amounted to 30 degrees in spite of the fact that the temporal rotation of each eye seemed normal. Under thorough cycloplegia the eye-grounds were found normal and the retinoscope established his refractive status as R. — i.oo sph. — 75 cyl.axis 45 degrees L. — 0.75 sph. — 50 cyl.axis 180 degrees. ESOTROPIA. ' 167 With his correcting glasses 10 degrees of the deviation disappeared, leaving 20 degrees in evidence and it so remained at the end of a year. Since that time some education of the fusion faculty has been accomplished and today (after five years) the deviation equals 10 to 12 degrees. He now has a fair chance to reach manhood with an approximately straight pair of eyes and with- out having been subjected to operation. Necessarily such cases are rare. The usual condition is that of a somewhat subnormal fusion faculty that is embarrassed in its evolution by an unequal compound hypermetropic astig- matism. Indeed, it is our feeling that this is the usual complex in the vast majority of cases presenting themselves either in private or clinical practice. Congenital Paresis of One or Both External Recti. — As stated in the classification, this is to be distinguished from true congenital abducens palsy. It is not frequently encountered, but one should nevertheless be on his guard. For instance : Miss H. C, aged twenty-six, comes for advice as to her eso- tropia, which had shown itself mainly from her fourth year onward. At her sixth year she was refracted and for twenty years she had worn glasses that so lessened the esotropia as to entirely satisfy her as to her appearance. She showed 15 to 20 degrees of esotropia, varying from time to time. Her refractive status was typically H and Ah, for which she was wearing a good cor- rection. She preferred to fix wdth her right eye, although the vision was normal in both eyes. With the tropometer it was found that her temporal rotation in either eye was but 20 degrees (as against the normal 50). Homonymous diplopia was found in the extreme temporal periphery of both motor fields, although it was not noted until the light was 30 to 35 degrees from the median line. It would have been an easy matter to overlook the some- what defective temporal rotations in these eyes. Muscular advancement of both external recti in this case entu-ely corrected the defect. Obstetric Injuries to the Eyes. — Within recent years Wolff and von Sicherer have studied the eye-grounds of newborn children 1 68 FUNCTIONAL ANOMALIES. and have found numerous instances of retinal hemorrhages not only in children who were instrumentally delivered, but also in those who were born without the use of instruments. These facts may have much bearing on the genesis of esotropia. If a child should be born with an extensive retinal hemorrhage in- volving the macular region and this hemorrhage were imper- fectly absorbed it is not difficult to conceive that there might be sufficient hindrance to the normal evolution of binocular vision to induce suppression of the images from that eye such as occurs in children with a defective fusion faculty, in which event the Fig. 6o. — Crossing of visual axes. eye so affected might eventually deviate from parallelism. If the child had a congenitally strong fusion faculty the eyes would be held parallel, but the child would grow up with a congenital ambly- opia. It is probable that this is the explanation of that class of cases that come to report from time to time, of amblyopic eyes seem- ingly without any ophthalmoscopic change and yet revealing a well marked central scotoma. It must be borne in mind always that the image of the object engaging the attention of the patient falls upon the fovea of the fixing eye, and upon some portion of the retina to the nasal side of the fovea of the squinting or deviating eye. Hence, the visual axes are not, strictly speaking, inclined toward each other; but the axis of the fixing eye is directed straight at the object, while that of the deviating eye intersects that of the fixing eye at a point nearer the face than the object; in other words, both eyes are not abnormally converged at the same moment (see Fig. 60). ESOTROPIA. 169 The burden of the convergence is borne by one eye only, trans- ferable under some conditions to the other, but never mani- fested simultaneously in both. This statement is true only of the properly so-called functional esotropias, and excludes paralysis of the external muscles and association paralysis. Esotropia is mmiocular (or constant), and binocular (or alter- nating). In the former, one and always the same eye, under all circumstances is used for fixation, while the former eye deviates. In the latter, either eye is used indifferently for fixing, and the squint is instantaneously transferred to the eye not so used. Monocular Esotropia. Monocular esotropia is characterized by (i) lowered vision or even amblyopia of the squinting eye; and (2) invariable fixation of the other eye. Diagnosis. — The methods that take into consideration the apparent deviations of the visual axes are at times misleading. For example, the angle alpha made by the intersection of the optic with the visual axis may be abnormally ^^L^^ small, giving the appearance of in- ■BWBL ternal strabismus, while the muscles 43 ^ J may be in equilibrium. Too, the interpupillary distance, the shape of the orbit, the size of the commissure and other anatomic peculiarities should always be taken into consid- eration. The three facts that should be de- termined in every case of esotropia are the vision, the degree of deviation, and the refractive status. Vision. — In children under three years of age, estimate of the vision is most unsatisfactory and generally impossible. Between the third and the seventh year, some form of object test card will be necessary. Fig. 61. The one illustrated we have found of great service. Naturally much tact is required in handling these little people, but judg- ment and patience will be amply repaid when the cooperation of the child is secured; this once accomplished all the rest is easy. In esotropic children under six years of age, the vision in the 170 Fig. 61. — Reber's object or kin dergarten test card. MONOCULAR ESOTROPIA. 17I deviating eye will seldom be found less than 5/30. After the seventh year and on up to puberty it frequently falls to 5/60 and at times to 2/60 or 3/60. Amblyopia. — No term in all ophthalmic literature has been more loosely used than this term amblyopia. While it admittedly means "indififerent vision," few writers seem to have stated just what degree of loss of vision shall justify our use of the term amblyopia. Inasmuch as vision of at least 1/4 (5/20 or 20/80) is essential to permit comfortable use of an eye for reading, it would seem justifiable to fix that as the arbitrary mark. Vision of less than 5/20 or 20/80 could be definitely set down as ambly- opia and more than that as not amblyopic. It is understood that the ophthalmoscope shows no opacities in the media, and that the details of the eye-ground conform in every particular to the normal standard, although the field of vision, as above stated, is sometimes defective, especially in its central portion. That no minute anatomic changes of the optic nerve occur in the fovea or in the foveal fibers seems clear from the report of several cases in which an amblyopic squinting eye was restored to useful vision in the course of a few weeks by its enforced use. Again, the error of refraction of the amblyopic eye not infrequently differs very little from that of the seeing eye, certainly not enough to account for that grade of defect which will exclude it from all participation in vision. It is probable that in consequence of a functional (but not anatomic) defect in the basal ganglia or the cortical centers for vision, acting in conjunction with a degree of hypermetropia high enough to disrupt the association of con- vergence and accommodation, one eye has been excluded from vision and its function held in abeyance. Whatever the ex- planation may be, it is true that amblyopia is invariably associated with monocular squint, that it limits the squint to one eye, and stands in the way of a scientific correction of the muscular error, since binocular vision is practically unattainable. In some cases restoration to parallelism of the visual axes can, in fact, be effected, only for a brief period however, since the blurred image seen by the amblyopic eye interferes with the clear 172 FUNCTIONAL ANOMALIES. one seen by the good eye, and in the interest of good vision the in- distinct image comes to be disregarded and an internal or external deviation is developed. Improvement has been reported as the result of exclusion of the good eye, enforcing education and training by constant use of the other; it has also been claimed as a result of operation, but in our experience the means often successfully employed to correct squint in childhood without operation, such as atropin, bandaging of the good eye, etc., have proved indifferent in curing amblyopia, and the hope that vision may be restored to a practical and useful extent by these means has not been entirely fulfilled. Amblyopia does not signify blindness (for which the obsolete word is amaurosis), and when not qualified by an adjective, such as toxic, renal, etc., indicates simply that the patient's vision is defective from no known causes. The use of the word should be limited to those eyes whose vision is lower than 20/80. Perseverance scientifically applied will often be re- warded by a decided improvement of vision by correcting lenses.^ Measurement of the Deviation. The means employed for the measurement of the deviation are: a. inspection, b. the cover test, c. linear measure, d. the perimeter or arc measurement, e. the tape measurement or tangent measure- ment, f. the diplopia test, g. the tropometer or rotational test. a. Inspection. — Inspection will show a want of coordination of the visual axes by the fact that the sclera of the temporal side of the deviating eye is exposed in greater extent than that on the nasal side; furthermore, that the cornea is deflected toward the nose. b. Cover Test. — The patient fixes the gaze on some object 20 or more feet distant. The cover or screen is then placed over the fixing eye compelling the previously deviating eye to fix, when it will be seen to move from 2 to 5 mm. to reach the proper position ' Should the reader desire to pursue the theories of amblyopia farther than they are here discussed, he is referred to the papers of Hansen Grut, Schweigger, Schmeich- ler, Priestley Smith, Parinaud, Javal, Worth and others. MONOCULAR ESOTROPIA. 1 73 for fixation. The degree of deviation can be estimated with fair accuracy by interposing prisms with their bases out, increasing in strength until all movement of cither eye (as the screen is carried to and fro in front of the eyes) is abolished. The prism strength required to stop the movement of either eye is the measurement of the deviation. c. Linear Measure. — Years ago von Grsefe devised a small curved ivory scale marked in millimeters to be laid against the lower lid and the deviation then read oflf in millimeters (Fig. 62), but, as Landolt insists, it is not exactly scientific to speak of an angular Fig. 62. — Graefe's strabismometer. deviation in Hnear terms. This may be obviated by utilizing the images formed by the corneas when a strong light is thrown on them. With the light directly over the patient's head, a re- tinoscopic mirror will produce quite a bright corneal image if thrown upon the eyes from one meter's distance. Hirschberg estimated that this reflection image, if seen at the corneal limbus represented a deviation of about 45 degrees; if on the sclera it is 60 to 80 degrees; if midway between the limbus and the margin of an average sized pupil it is about 15 to 20 degrees, and if at the outer edge of the pupil about 10 degrees. With practice a fairly accurate estimate may be made. d. The Perimeter or Arc Measurement. — The patient is seated at the perimeter just as for ordinary perimetry only that both eyes are kept open. The non-squinting eye is then fixed upon some object at infinity directly in line with the center of the perimeter arc while the observer moves a small electric light along the arc of the perimeter. The image formed by this light on the cornea of the deviating eye is studied and the light moved backward and 174 FUNCTIONAL ANOMALIES. forward along the arm of the perimeter (which should be in the horizontal meridian) until the tiny corneal image rests directly in the center of the pupil of the deviating eye, when the observer notes at what degree on the perimeter arc the light is resting. This is the true measure of the deviation in degrees. (See Fig. 63). The perimeter method is easily applied in grown children and adults, but is of little use in children under six years of age. Fig. 63. — Arc measurement of the deviation in esotropia. The arc of the perimeter is in the horizontal meri(iian. e. Priestley Smith's Tape Measure Method (tangent measure- ment). — In a darkened room the observer takes a position one meter from the seated patient, over and back of whose head is a light. The observer is armed with a retinoscopic mirror and a tape measure marked in centimeters. The patient gazes at an object at infinity. The light is thrown by the mirror on the deviat- ing eye when the corneal image will be seen near the limbus of that eye. With the tape measure held at zero against the handle of the retinoscopic mirror, the observer moves his disengaged hand horizontally away from the direction of the deviating eye, directing the patient to follow his moving hand (through which the tape measure is allowed to slide) until the deviating eye is MONOCULAR ESOTROPIA. I75 brought into such a straight ahead position that the corneal image rests just in the center of the pupil of that eye. Then the obser- ver's moving hand pinches the tape measure wherever it may be at this instant. The number of centimeters the moving hand has covered on the tape measure records the number of degrees of deviation present. This method is quick, accurate, convenient and quite as applicable in a three year old child as in an adult, f. The Diplopia Test. — By determining the relation of the image of the squinting eye to that of the fixing eye, the diagnosis of the actual position of the squinting eye and the degree of vari- ance of its visual axis from parallelism can often be made. In amblyopics, the surgeon experiences the greatest difficulty in forcing the patient's recognition of the image of the amblyopic eye because, as has already been stated, he never complains of diplopia, nor is he ever conscious of the false image of any object. Therefore, examination by means of double images would seem to be impracticable, but in our experience persistent efforts have frequently accomplished the end sought. At first, the patient absolutely refuses to acknowledge the false image, but with the aid of strong prisms, base out, before the squinting eye (bringing the false image nearer to the true) and by means of colored glasses (particularly those that render the true light dull and indistinct) perseverance will finally be rewarded with the acknowledgment that the object has its shadow. Having once secured this rec- ognition, the subsequent steps present no difficulty. The prisms, bases out (and bases down if necessary), before the squint- ing eye which will fuse the images will be the prismatic measure of the deviation. By pursuing this course another important factor in the diagnosis, viz., the difference of elevation of the true and false light, is readily and accurately determined.^ The false image will be on the side of the squinting eye (homonymous) and often below that of the true eye. The lateral deviation equals 20 degrees to 40 degrees or more, and the vertical difference is usually overcome by a prism of 3 to 4 degrees. This determina- * Cases that prove exceptions to this rule are those of false projection (the so- called second fovea), and those of mental incapacity. 176 FUNCTIONAL ANOMALIES. tion of hypertropia is necessary to the treatment, even though the result of the operation can only be cosmetic. Clinically, we have found that vertical squint is not transferred with the lateral in cases of high amblyopia, the eyes retaining the same relative position even when the sound eye is covered. g. The Tropometer. — While this is a supplementary test the information furnished by this instrument is of value in indicating the exact power of temporal rotation of esotropic eyes. Its findings gener- ally show subnormal power of temporal remparaiio-, 7 • rotation m such cases. The motor fields here shown are from a typical case of monocular esotropia (Fig. 64). Another supplementary test is the Fig. 64.— Tropometric fields deviometer of Worth (modified by in a case of monocular esotro- Black), but it ServeS no purpoSC not pia (right eye deviating eye). ^ ' ^ ^ ^ The average normal rotations fulfilled by the foregoing testS and are upward •?6, downward ^2, • , i.-i- cc. i. temporalward48,nasalward5o: Simply multiplies office apparatus. Treatment. — The management of monocular esotropia is nonoperative in the developmental and operative in the confirmed stages. The nonoperative treatment is applied with the hope of ac- complishing two purposes, namely: the subsidence of the squint and the cure of the amblyopia. Early in the history of the squint the peripheral cause, hyperopia, can be set aside by paralyzing the accommodation, thereby silencing the abnormal stimulus to convergence always consequent upon the unconscious but un- ceasing overaction of the ciliary muscle. It is not uncommon to see an esotropia disappear in small children after two to three months paralysis of the accommodation and use of a proper cor- rection. The drug usually employed for this purpose, and the one best borne by children without serious results after prolonged application, is atropin, which it must be said is not without its disadvantages. The pupils partake in the paralysis and become widely dilated, giving rise to photophobia; the follicular glands of the conjunctiva take on a hypertrophic inflammation, and the MONOCULAR ESOTROPIA. I77 squint, for a time at least, seems to be increased because, although the impulse to accommodation is not interrupted, accommodation itself (response to the impulse) is impossible. On the other hand, the associated impulse to convergence is greater because of the patient's efforts to correct his defective vision by calling urgently on his ciliary muscles. However, this effect of atropin is transient and may with safety be disregarded. It may be applied either to both eyes or only to the fixing eye. In the latter case induce- ment is given the patient to use the squinting eye, provided that its vision is better than that of the fixing eye when atropinized. For the same reason periodic wearing of a bandage or screen over the sound eye is advocated to promote the retinal functions of the deviating eye. It is our opinion that in monocular squint with its attendant amblyopia, this preliminary treatment while not often effectual in curing the deformity or in restoring bin- ocular vision, is certainly useful in preventing an increase in the ametropia and a decrease in the vision of the amblyopic eye. The therapy of esotropia further includes the optical correction of the refraction error, even in very young subjects.^ This should be invariably determined by the ophthalmometer and retinoscope and in children under six years of age it is the part of wisdom to bind off one eye while retinoscoping the other. No satisfactory treatment of esotropia in children can ever be instituted without the use of the retinoscope under thorough cycloplegia. A full correction, or as nearly full as possible, should be worn constantly. The beneficial effect of glasses may be increased by the joint use of atropin. And yet, however essen- tial these means may be in the early treatment of monocular eso- tropia, they are seldom final, either singly or jointly. As long as the vision of the fixing eye is more acute than that of the squint- ing eye, the patient will prefer to use the better organ, and neither the squint nor the amblyopia, will be cured, although much prog- ress in this direction will often be secured by employment of the stereoscope, as advocated by Landolt or the amblyoscope as used * Gould has recently {Phila. Med. Jour., May 18, 1898) reported cases in which glasses were successfully worn for squint as early as the twenty-ninth month of life. 12 178 FUNCTIONAL ANOMALIES. by Worth (see Fig. 65) for education of the fusion faculty. The latest model of the Worth amblyoscope is arranged with a double rheostat so that the intensity of illumination in either tube can be perfectly controlled by simply pushing a steel collar to and fro. In this way the intensity of retinal stimulation may be beautifully equalized. No other device at present offers this advantage. Three sittings a week for four weeks should be required of the patient. If at the end of this time no improvement is noted surgical interference must be considered. At this point several questions are suggested, viz.: At what age is operation to be recommended? To what muscles should the treatment be directed ? Should it include one or both eyes ? Fig. 65. — Worth's amblyoscope with rheostat. Authorities state that six years is the earliest age at which operation ought to be performed, and that nine to ten is the most advantageous. The advocates of early operation urge that a restoration to parallelism of the visual axes will prevent the devel- opment of amblyopia, which they claim ensues from non-use. The objections to early operation are: the immaturity of the globes, the natural increase in the power of the muscles of growing children, the impracticability of accurately estimating the degree of the squint, and hence the effect desired or secured by operation; also the fact that when tenotomy of the internal recti is performed crudely, too extensively, or at too early an age, divergence often ensues between the twentieth and thirtieth year. In esotropia, MONOCULAR ESOTROPIA. I 79 as in esophoria, the surgeon has the choice of tenotomy of the interni, or advancement of the externi, or a combination of both. Inasmuch as a scientific restoration of binocular vision cannot often be obtained in monocular squint, and as all procedures are carried out with the object of removing the deformity, it has been argued that attention should be directed mainly to the squinting eye. But tenotomy of the internus of this eye only will be pro- ductive of little good, and it will nearly always be necessary to tenotomize the internus of the other eye also. While in many instances the visual axes may be brought to parallelism by these two operations, it will often be accomplished only by such thorough division and separation of the interni from the neighboring tissues, that the effect is practically that of paralysis. In a few years the evil consequences of such measures crop out either in divergence of the amblyopic eye, or serious impairment of the inward rotation of both globes. The proceeding that appears to offer the greatest advantage, both immediate and permanent, is advancement of the externus of each eye, combined with a moderate tenotomy of the interni of the squinting eye. Subse- quently, if necessary, tenotomy of the internus of the fixing eye may be performed. If vertical deviation co-exist, as it nearly always does, it is good practice to divide the superior rectus of the squinting eye first, since it has been shown in many cases that when hypertropia has been eliminated esotropia dimin- ishes, and sometimes even disappears. Alternating Esotropia. Etiology. — Alternating esotropia differs somewhat from the monocular form in its clinical aspects and its treatment. For instance, disease of the foveal fibers of the retina and optic nerve of one eye (the result of congenital causes, of accidents during de- livery, possibly of non-use of the eyes) by some authorities given much prominence in the development of the monocular, play very little part in the alternating form; in the latter variety, therefore, amblyopia (in its strict sense) is not to be expected. Moreover, in alternating esotropia the deviation is perfectly and readily transferred from one to the other eye. Finally, the results of treatment, both in permanently correcting the deviation and in re-establishing binocular vision, are infinitely more favor- able in this variety. As to etiology, it may be said that occa- sionally an inherited deficiency or coordination in the cortical centers of fusion is undoubtedly a factor contributing to the loss of binocular fixation, although the usual exciting cause is a hypero- pia of from 2. GO to 4.00 D. The former is plainly shown in the following case: E. F. M., a seven-year-old girl is brought with a history of esotropia appearing during the second year of life. There was nothing in the history that would account for the deformity. The child would fix indifferently with either eye. The vision equalled 5/5 in each eye, the deviation measure 35 degrees, with both eye-grounds normal in every respect. Tem- poral rotation in each eye was somewhat defective. Under thorough cycloplegia the refractive status was found to be -|- 0.50 sphere in each eye. Plainly the refractive error was not an etiologic factor. Investigation showed that the child's fusion ' Synonyms. — Concomitant internal squint or strabismus, alternating internal squint or strabismus, and insufficiency of the externi. (It is to be hoped that the expressions "concomitant" and "strabismus" as applied to esotropia, will soon be discarded. 180 ALTERNATING ESOTROPIA. l8l faculty was practically nil. Fusion training was tried for eight weeks, but without avail and operation became the only resort. Advancement of each externus gave a most satisfactory result. Exceptionally, the degree of hyperopia is much higher than 4.00 D., but esotropia is uncommon in very high hyperopia, unless the latter is attended with congenital disease of both fovese (Reber). As in esophoria and monocular esotropia, the overaction of the ciliary muscle necessary to acute vision stimulates the nucleoli of the 3rd nerve, and through them the muscles governed by the nerve, with a resultant inward and up- ward deviation of either eye indifferently; therefore, the squint is transferable. (Many of these cases conform absolutely to the requirements of Bonder's theory; that is, they are accommodative esotropias). Diagnosis. — The methods employed in the recognition of monocular are equally applicable to binocular esotropia, and their detailed description may, therefore, be omitted. As has been said above, fixation is quite indifferent, and the slight- est circumstance may suffice to so disturb it that the squint is taken up by the eye which, up to that moment, had been fixing. It cannot be too strongly emphasised that the upward squint is also transferred, as can be readily demonstrated by testing with glasses of different colors. For instance, with a red glass before the right eye and a blue glass before the left eye, recognition of double images will be almost immediate. If the right be the fixing eye, the blue light (L. eye) will be to the left side of and below the red light. However, if the patient's attention is now directed to the blue light, making it the fixing eye, the red light (R. eye) will be to the right of and below the blue one, clearly showing that each eye deviated not only in, but also up, when the other was fixing. The lateral deviation varies from 20 degrees to 30 degrees and sometimes even to 50 degrees, while the vertical deviation is usually corrected by a prism of from 3 to 4 degrees. In conducting this test, the surgeon will sometimes have difficulty in bringing the patient to recognize the two images, but if diplopia can be induced no method of diagnosis is more accurate. In children of suitable l82 FUNCTIONAL ANOMALIES. age for operation the false light will occasionally be suppressed at first, but after some little effort it will be recognized. It will thus be seen that a description of esotropia naturally in- cludes a description of hyperesotropia, and that esotropia as a pure lateral deviation rarely exists as a functional anomaly. The upward deviation has been noticed by few and overlooked by many writers, for the reason that the inward turn gives rise to a deformity so great that it masks the comparatively insignificant upward turning. Treatment. — As has been said in the treatment of monocular esotropia it is not uncommon to perfectly and permanently cure this deformity in small children even when alternating, by paralyz- ing the accommodation for some months early in the history of the sc[uint. It is scarcely necessary to add that the patient should wear, from the earliest possible moment, an accurate correction of his hyperopia or hyperopic astigmatism. The act of binocular vision is favored by the normal bilateral use of the accommo- dation which the glasses re-establish and by the increased visual acuity which they confer. These should never be omitted, even in those in whom the deviation seems to be fixed. Failing in these means, resort must be had to Operation. — It may be well to repeat that squint is not pri- marily a defective muscular condition, and even less is it an affec- tion that can be attributed to any one muscle. It is a matter of convergence power as related to divergence power, or still more accurately it is to be referred to the muscular response of excessive or deficient nerve stimulation. Therefore, it would seem, reasoning a priori, that the remedy is not to be found in opera- tion on either the interni or the externi, but in regulating or co- ordinating the stimulus to convergence and divergence so that these functions may respond relatively equally and hold the visual lines in horizontal equilibrium. This is perfectly true and is carried out in practice, removing — by means of cycloplegics, convex lenses, muscular and fusion exercises and the efforts to improve vision — the causes of esotropia. But these measures often fail and operative measures only remain. In our judgment ALTERNATING ESOTROPIA. 183 we have, not the choice between tenotomy or advancement when the convergence exceeds divergence by 20 degrees or more, which is always the case in functional esotropia. To cut the interni at their insertion so that an effect of 20 degrees or more is obtained Fig. .66. — Holmes' stereoscope. means separation from the sclera not only of the tendon, but also of all the subsidiary fibers to the sides of and under the tendon. Such an extensive operation entails surely a decided loss of inward rotation, a permanent weakening or loss of the function of the Wy-': / T I^^^^^^H L Fig. 67. — Bar reading. muscle,"a retrogression of the caruncle and a prominence of the sclera on the nasal side, and possibly proptosis. Parallelism of the visual axes and the correction of the deformity are the immediate apparently satisfactory results. Later, however, the i84 FUNCTIONAL ANOMALIES. eyes are likely to diverge, in which event coordination for all distances is lost. We, therefore, recommend double advancement. By this operation the previous excess of convergence is neutralized by the acquisition of greater divergence so that by the use of the eyes under proper conditions (hyperopic correction) equilibrium of the lateral muscles is secured and maintained. Inward rotation is not curtailed and no fear need be entertained of a subsequent divergence. At the same time the grasp and control of the whole cone of muscles on the globe is materially increased. By the Fig. 68. — Remy's diploscope. operation the images of the two eyes are brought closer together and the fusion power is stimulated to fuse the images. The opera- tion on both muscles should be performed at the same sitting. It may be necessary in cases of the highest grades of esotropia (internus contraction, internus spasm) to later tenotomize one or both interni in addition to the operation of advancement, but this step should be taken only after the lapse of several months, when it will be learned positively that no further increase of divergence may be looked for, as a result of the advancement. For some days, or even some weeks, the operator may be disappointed that ALTERNATING ESOTROPIA. 185 the results are not all that he had hoped for — it is well known that the final degree of divergence is not reached until some weeks after the advancement. This interval should be utilized to aid the development or the increase of the fusion power by exercises of various kinds. Indeed, stereoscopic exercises with the Holmes stereoscope are often of service both before and after operation. Bar reading after the operation (see Fig. 67) is much to be rec- FiG. 69. — Bishop Harman's diaphragm test. See also Fig. 26. ommended. The diploscope of Remy (Fig. 68) or Harman's diaphragm apparatus (Fig. 69) are both convenient not only to learn whether binocular vision has been secured by the opera- tion, but also as a means of training the fusion sense. These same exercises are of value in monocular esotropia both before and after operation. EXOTROPIA Exotropia may be 1. Organic, as a result of destruction of the nucleus or trunk of the 3rd nerve either from traumatism or disease; also as a result of direct traumatism to one of the internal recti. 2. Partly organic and partly functional, as in partial loss of vision in one eye from anisometropia or antimetropia, or from in- jury to the eye; in excessive myopia from elongated eyeballs, in those exotropias the result of too free tenotomies for esotropia in childhood, and in high-grade orbital asymmetry. 3. Purely functional, due to the influence on a congenitally w^eak fusion force (desire for binocular vision) either of some re- fraction anomaly (usually myopia) or of the natural divergence of the orbital axes in adult life. Classes i and 2 may be binocular, although the deviation is usually confined to one eye. Class 3, the truly functional exotropias, are almost always binocular, and maybe defined as a partial loss of the power of con- vergence, although the vision of both eyes is alike or nearly alike. The organic exotropias (Class i) have been disposed of in a pre- vious chapter; also such of Class 2 as are mainly organic in type. Only those of the second class, depending upon the elongated eyeballs of excessive myopia, or upon asymmetrical orbits, will be mentioned here, and but briefly, the main question under consideration being true functional exotropia. As has been shown in the previous chapter, esotropia is an acti\e phenomenon growing directly out of overaction of the muscles under the domination of the 3rd nerve. Exotropia, on the other hand, while due to an anomalous condi- tion of the same group of muscles, is a passive phenomenon, and may in general terms be regarded as a relaxation of all the muscles 186 "~ EXOTROPIA. 187 governed by the 3rd nerve, giving rise to divergence of the visual axes. ^ It commonly affects both eyes in the earlier stages, in which case it is known as bilateral, binocular or alternating exotropia. In its final phases it is usually confined to one eye, when it is known as monolateral or monocular exotropia. Etiology. — While the etiology of the affection sometimes seems obscure, the fact seems to stand out that its origin is more or less closely bound up with the presence or development of myopia, which, because of the increased length of the eyeballs and by lessening the demands on accommodation (and hence action on the part of the ciliary branch of the 3rd nerve) lessens in like degree the action of the remaining muscles supplied by the 3rd nerve, and the eyes tend in the direction given them by the normally innervated external rectus and superior oblique muscles — namely, out and down. Thus a deviation of the visual axes not only out, but also helow the horizontal line is likely to be encountered in this, the myopic variety of exotropia. Should the anomaly be but a functional one up to the time of puberty or soon thereafter, the deviation tendency is likely to then become a true deviation because of the natural divergence of the orbital axes, which, as has been shown by Weiss, is the feature in the growth of the adolescent and adult orbit. To this latter fact, and to occasional overaction on the part of the superior oblique and external rectus muscles, must be ascribed the exotropia found in the presence of emmetropia and hypermetropia. It will then be readily seen why exotropia is rarely met with in children (save in high congenital myopes) and why it commonly reveals itself during adolescence or early in adult life. Too, the slow departure of the accommodation in the youthful myope, and in other cases the very gradual increase in divergence of the orbital axes, give to the approach of exotropia an insidious form, ' The condition is also known as external squint, divergent squint, strabismus divergens, concomitant or alternating squint or strabismus, and insufficiency of the interni. It is to be hoped that these synonyms will soon give way to the nomenclature here adopted. 105 FUNCTIONAL ANOMALIES. while esotropia, on the other hand, is relatively rapid of develop- ment. Furthermore, esotropia in the child often becomes esophoria in the youth and may pass through the various degrees of esophoria into muscle-balance when maturity is reached; whereas exotropia in the young or adolescent can only become accentuated as the years wear on. The natural tendency of myopic eyes toward divergence is caused in part by the elongated globes, which must add to the weakness of the adducting muscles in all near work, and in part by the absence of the impulse to accommodation to aid convergence. Very often there is marked irregularity or inequality in vision, and in some cases one eye is so nearly blind that it wanders outward simply in obedience to the tendency impressed upon it by the outward direction of the axis of the orbit. In any case there must co-exist a lack of power of the adductors to render the deformity possible, while refractive conditions play a role which has been sufficiently explained. Symptoms. — The only noteworthy symptoms of exotropia are the deviation, the occasional amblyopia, and the defective vision consequent upon the myopia which usually completes the picture. The deviation itself produces no distress and is often borne for years without any special inconvenience to the patient. Rarely is diplopia present, and then mainly when exophoria is passing over into exotropia. Even under such circumstances the patient is only occasionally conscious of diplopia, and while some pa- tients may be educated into seeing double images, in most in- stances it is difficult to excite them. Amblyopia, in the sense of the amblyopia of esotropia, is only rarely a symptom of outward deviation, and if it does occur it is a question as to whether it is of the same origin as the esotropic variety. It has been argued that it grows out of suppression of the image of the deviating eye, habitually resorted to by the patient to avoid the confusion of diplopia, and that if suppression of the images falling upon the retina of the unused eye can be so readily learned as it is by microscopists, ophthalmoscopists, astronomers and others, it seems reasonable to assume that it is re- EXOTROPIA. 189 sorted to unconsciously, but none the less surely, by exotropics (as also by the victims of longstanding ocular palsies or pareses) to avert the confusion of diplopia. We have no means of learning whether the esotropic infant or child has ever seen well with its deviating eye before that eye deviated, nor whether the com- plexity of functions that issue in binocular vision have ever been thoroughly acquired and brought into harmonious automatic relations. Exotropia, on the other hand, seldom reveals itself before puberty — long before which time binocular vision has be- come one of the cardinal functions of the central nervous system. Let it be remembered that the performance of binocular vision calls for harmonious synchronous action on the part of areas in the motor region of the cortex, also on the part of a large portion of the occipital cortex, and lastly on the part of the 2nd, 3rd, 4th, and 6th (namely four out of twelve cranial) nerves. With this proposition in mind, it is not difficult to conceive that many esotropic children have never thoroughly acquired this complex function, and that in such children a moderate degree of hyper- metropia suffices to so disturb the act that the brain finally abandons the struggle. Hence we have spoken of a congenitally weak fusion-force. Similarly in exotropia (at least of the myopic variety), when the impulse to accommodation is no longer excited, another disturbing factor has been obtruded on the act of single vision, and the outward deviation of the eye or eyes is the signal of the surrender of the higher centers. However, in exotropia we are dealing with eyes that have enjoyed a high degree of visual acuity, and deviation certainly means diplopia with its sequels unless one eye learns to disregard its images. Necessarily this has naught to do with the amblyopia of those outward deviations which are the result of over-free tenotomies for esotropia in childhood, and which are to be regarded more as pareses of the operated interni than as true exotropias. It is proper to state that in exotropia there may be ocular symp- toms, but these commonly result from the refractive error present, and generally disappear after its correction. Diagnosis. — The diagnosis of exotropia rests upon much the IQO FUNCTIONAL ANOMALIES. same methods as those for esotropia — ^namely, inspection, the cover- test, with and without prisms, the study of the double images (when they can be induced) with and without prisms, and the tape measure method. Simple inspection will in most cases not only determine the presence of the anomaly, but may also show which is the fixing eye and what the probable degree of deviation. Resort, however, is generally to be had to the cover-test as follows : The patient is seated facing a candle-flame or some similar small bright object 20 or more feet distant. A small piece of card- board is then carried from one eye to the other and if each eye fixes as its fellow is covered, the squint is of the alternating variety. When both eyes are uncovered it will be found that the patient consciously or unconsciously uses either the right or left eye by preference for fixation. We therefore speak of it as the fixing eye. The fellow organ then assumes a varying degree of divergence. Should the deviation be of the monocular or monolateral variety, it will be found, on applying the cover-test, that the deviating or amblyopic eye makes little, if any, movement when the fixing eye is covered. Alternating exotropia may be measured with fair accuracy by using prisms in connection with the cover-test. Having the patient fix on the candle-flame or other object 20 feet distant, a 10 degree prism, base in, is brought before either eye, preferably the fixing one. Applying the cover-test, it will be found that the excursion of each eye as the cover is shifted from side to side is much diminished, and by increasing gradually the prism strength, base in, a degree will finally be reached at which both eyes are apparently steady as the cover moves back and forth. Not infrequently it will be found that a vertical devia- tion co-exists, when it will be necessary to learn the prism needed to arrest the vertical as well as the lateral movement. The prism or prisms required to suppress all movement of the eyes under cover, will be the prism measurement of the deviation; and if in carrying out the test, very high degree prisms are needed, the effect can be divided between the eyes. Those not familiar with the test, will do well to guard against over-correcting with prisms, as this will induce esotropic movement under the cover and thus lead the EXOTROPL\. 191 surgeon into serious error. The test is purely objective and of great service.^ When double images can be excited, we have another valuable test at hand. By coloring the image of the fixing eye v^dth a cobalt glass, the relative position of the images is easily studied, and the degree of the prism that will bring the images into a horizontal or vertical line (or both) readily learned. However, this measure is applicable only to those patients in whom double images can be induced, and who can cooperate mentally with the surgeon in the study of the case; whereas, the cover-test, combined with prisms, renders the surgeon absolutely independent of the patient, and is of signal service in all cases of alternating exo- tropia irrespective of age or mental condition. The tape measure method is applied in the same manner for measuring exotropia and with the facility as in esotropia. Moreover, as most exo- tropics are adults the perimeter may be easily employed for the arc measurement of the deviation. Treatment. — The management of exotropia is optical and operative. At first it would seem that treatment might also be therapeutic; that if atropin serves to interrupt the pathologic process in the early stages of esotropia, pilocarpin or eserin ought, logically, to be of service in the same period in exotropia. The- oretically, this reasoning is correct, but unfortunately it is not borne out by clinical facts. In esotropia, we are dealing with a force that needs curbing, and atropin is the ideal agent. In ex- otropia, we have to do with functions (accommodation and con- vergence) that are waning, or with conditions that are the result of anatomic changes (divergence of the orbital axes, and elonga- tion of the globes). The fact is that myotics by stimulating ac- commodation alone would rather lessen the associated stimulus to convergence, and thus add to the divergence of the eyes. Moreover, it would seem that the instillation of a very weak mydriatic might, by inducing extra stimuli to the ciliary muscle, incite the adductors to action, and hence be of service in the early * The same mistake may be just as easily made in estimating the prism degree of esotropia or right or left hypertropia. 192 FUNCTIONAL ANOMALIES. Stages of exotropia, although there is no record of such treatment directed to early exotropia. The optical treatment of exotropia may be affected by correct- ing lenses alone or in combination with prisms. The greatest care should be observed to learn the exact static refraction in every case, when the following rules are in force :^ For non-presbyopes. All myopes under 6 D. to be given a full correction of their optical defect, that the accommodation may be forced into action. It will often be of advantage to assist the accommodation at first with one drop of a one grain to the ounce solution of pilocarpin muriate in each eye three times a day. Myopes^ of over 6 D. to be given the fullest possible correction consistent with any degree of comfort in work at the near point. Pilocarpin is also of service in enabling these patients to become accustomed to the new conditions imposed. Hypermetropes of whatever degree to be given the weakest spherical correction consistent with comfort in working at the near point. Presbyopes to be given the strongest minus spherical (if myopes), or the weakest plus spherical (if hyperopes) that will enable the patient to conduct work at 13 inches, with pilocarpin (or eserin) again as a synergist. The object of all the foregoing measures is to induce action of the ciliary muscle in the hope of arousing an associated stimulus to the adductors, and thus lessening the divergence.^ If eight to twelve weeks' constant wear of the correcting lenses does not dissipate the exotropia, training of the convergence after the method advised in the chapter on exophoria will be in '■ Refraction under complete cycloplegia. - In a twenty-year-old young woman who came under our care, wearing— lo.oo for distance and — 6.00 for near work, the patient was relieved entirelyof her asthen- opia and incipient exotropia by two months use of — 13.00 D. S. — i.oo degree Cyl. 180 in each eye (her full correction), the employment of pilocarpin as above, and training of the convergence with prisms. ^ It should be mentioned that this adaptation of the correcting lenses to the exo- tropia applies to their spherical components only. Any cylindrical element neces- sary should be prescribed in its full static strength. EXOTROPIA. 193 order, bul this is feasible only in the lowest j^rades of exotropia where binocular vision is still possible. Anything over 15 degrees falls out of this class. As a last optical resort, streoscopic train- ing of the adductors may be tried after the method of Landolt, and some few patients will respond to this method of educating the fusion impulse after a.11 other methods have failed. Finally, if after optical correction, the deviation be less than 15 degrees, and does not respond to convergence training, or if it is over 15 degrees, operation is the final resource. Inasmuch as we are dealing with a passive phenomenon, shortening of the relaxed muscles is indicated, rather than tenotomy of their antagonists, hence advancement is preferred to tenotomy. In monolateral exotropia, the deviating eye should always be approached first. If vertical deviation co-exist, it should be remedied before proceed- ing to advancement of the internus of the squinting eye, and if these two steps leave a residual deviation, tenotomy of the ex- ternus of the squinting eye may be performed. Any deviation then remaining must be met by advancement of the internus of the sound eye. Rarely will it be necessary to go on to tenotomy of the externus of this eye. In binocular exotropia, the muscles to be attached are taken up in the following order: Any vertical imbalance must be first corrected; efforts to restore the lateral balance are then made by advancement of the internus of the eye which does not fix; or, if fixation be indifferent, by advancement of the internus of that eye which presents the poorer corrected vision. If this prove in- sufficient, advancement of the internus of the fellow-eye becomes necessary, and if external deviation persists despite all these procedures, tenotomy of either or even both externi is in order. These latter measures, however, will be required only in the most aggravated exotropias. In those few cases of pure divergence excess with fairly well preserved convergence faculty (the so- called neuropathic divergence), which usually are associated with hypermetropic states of refraction, tenotomy of both externi may be done with much confidence. As a rule, exotropes who have once possessed the faculty of bin- 194 FUNCTIONAL ANOMALIES. ocular vision are much more easily restored to its privileges than young esotropes who, in all probability, have never enjoyed good binocular vision. Hence, the prognosis of the operative treatment of exotropia is favorable, although the length of time necessary to bring the visual axes into coordination extends in some cases over several months. In those exotropias which are the result of too free tenotomies for esotropia in childhood, the divergence is usually monocular and is very wide, frequently reaching 55 or 60 degrees. In such cases it becomes necessary to do a wide resection and advancement of the internus with its overlying conjunctiva and surrounding capsule combined with tenotomy of the externus of the same eye. It is well to secure 5 to 10 degrees of over-effect in such cases, as a portion of the effect gained by operation is usually lost within two to three months after the operation. HYPERTROPIA Hypertropia, or true vertical deviation of one visual axis above the other, is not often encountered alone, but is usually associated with either esotropia or exotropia Admitting the relative infre- quency of pure uncomplicated hypertropia, one cannot but be struck with the meagerness of references to this anomaly in the most recent as well as in the older text-books on ophthalmology; nor does recent ophthalmic literature throw much light on the sub- ject. And the foregoing fact is even more striking when it is remembered that the same causes which underlie the functional or latent vertical imbalances (hyperphorias) lead directly up to and are as distinctly causative of, the actual vertical deviations or hypertropias. Etiology. — The ciliary overaction which in hypermetropic eyes often gives rise to a temporary esophoria or hyperphoria, may, under certain conditions, carry the anomaly from the latent or heterophoric class over into the actual or heterotropic phase; in other words, long perverted physiology finally issues in pathology. Just so long as the patient's fusion power asserts itself, just that long will the patient preserve binocular vision and in all likelihood present a train of ocular or reflex symptoms as the result of the extra output of nerve-force necessary tb maintain fusion. During this stage deviation tendencies only can be elicited — in other words, we are dealing with heterophoria; and many patients will carry a defect of this kind throughout life. But it frequently happens in childhood or adolescence that the supply of nerve-force necessary to fusion is not equal to the demand, and the muscular system of one or the other eye gives up the unequal struggle and latent tendencies become manifest, or heterophoria (functional turning) advances now to heterotropia, or actual turning. This variety results in the vast majority of cases either from uncorrected errors of refraction or 19s ig6 FUNCTIONAL ANOMALIES. from the change in the dimensions and direction of the orbital axes common to the time of puberty. Hence, hypertropia is similar in origin to esotropia and in many respects to exotropia, with cither one of which it is therefore nearly always associated, and upward is frequently associated with inward deviation as seen in Fig. 69. In hypertropia either the right or the left visual line may be habitually higher than the other (right and left constant hyper- tropia respectively) ; or each visual line may be alternately higher than the other — alternating hypertropia. Vertical squint is further classified as strabismus sursumvergens when the lower eye is the one that habitually fixes and strabismus deorsumvergens when the upper is the fixing eye. The preceding statements made in particular reference to the etiology of regular hypertropia (a deviation of one visual axis above the other) seem to us none the less appHcable to a certain remarkable class of cases, mentioned by Stevens,^ in which both visual axes deviate either above or below the horizontal plane when the head and eyes are in the primary position. Deviation of both axes upward is termed anatropia. That is, in anatropia, the right eye deviates up behind the screen or cover when the left is fixing, the left eye moving up also (instead of down as in hypertropia) the instant the cover is carried to that eye and the right eye is permitted to fix. Kata- tropia is present when with the same cover-test the excursion is down in both eyes. It is our behef that anatropia is an overaction phenomenon and that in all probability it is closely related to esotropia, a similar phenomenon. The excessive impulse which in hyper- metropia is sent to the ciHary muscle, affects in like manner the remaining muscles supplied by the third nerve, in consequence of which the eyes tend in the direction resulting from the combined action of those muscles, namely, up and in. If in esotropia the cover-test be used with the patient fixing on some point 20 or more feet distant, it w^ill be found that both eyes deviate not only inward, but also upward, as the cover is shifted from one to the ^Annals d'Oculistique, April, 1895. HYPERTROPIA. 197 Other eye (Fig. yoj. On the other hand, the ul)sence of impulse to the ciliary muscle of myopes (who commonly use little if any accom- modation) carries with it a very much diminished impulse to the other muscles governed by the 3rd nerve, and their resultant inaction permits the eyes to be deviated in the direction resulting from the combined action of the remaining ocular muscles (the external rectus and superior oblique), namely, down and out. The cover-test in such a case, provided binocular vision can be Fin. 70. — Upward and inward deviaiion of right eye. Such upward inward deviation of the right eye is sometimes seen with congenital paresis or palsy of the left superior rectus with spasm of the inferior oblique of the right eye (the associated muscle) especially if the eyes were carried toward the left. maintained, will show that both eyes deviate both outward and downward under the cover or screen as it is carried from one to the other eye. The organic hypertropias (generally paralytic), are seen prin- cipally in grave cerebrospinal disorders and have been considered at some length in the chapter devoted to palsies. These forms of hypertropia must not be permitted to obscure our ideas about true right and left hypertropia and strabismus sursumvergens and deorsumvergens, whose origin is closely bound up with anomalies of refraction and with the shape and development of the orbits. The following case is in point. M. B., a twelve-year-old girl, came with a history of a peculiar appearance about her right eye since her third year. No history that is worth while obtained. Inspection shows rather marked facial asymmetry. The right orbit measured 3 mm. less in the vertical and transverse diameters than the left, also the right eye was 3 mm. deeper in the orbit 198 FUNCTIONAL ANOMALIES. than the left. There was marked upward deviation of the right eye that measured 16 degrees constantly. At times esotropia was present, at other times it was not. It varied from 15 degrees to 20 degrees. With the tropometer the rotations of both eyes were as follows: R. E. Up 46 degrees. Down 57 degrees. In 45 degrees. Out 40 degrees. L. E. Up 38 degrees. Down 48 degrees. In 60 degrees. Out 35 degrees. She had never worn glasses. Her refractive status was R. + 6.00 sph.+ i.oo cyl. 90 degrees = 5/60 L.+ .50 sph.+ .37 cyl. 105 degrees -5/5 which was ordered for her when her esotropia disappeared entirely, the vertical element remaining. After 6 months use of the glasses, the vertical deviation remained at 15 degrees, when tenotomy of the right superior rectus was done with most gratifying results. Of course she continues to wear her glasses. S5rmptoms. — The symptoms of the earliest stages of hyper- tropia are largely those of hyperphoria. However, when the weak depressors or elevators have abandoned their fruitless task, the eye to which they belong will deviate in the direction of action of the stronger muscles, binocular vision will be lost and along with it will most likely disappear much of the patient's ocular and reflex discomfort. The resulting deviation which is the main objective symptom, is easy of recognition in most cases, especi- ally with the cover-test at 20 feet. The cardinal subjective symp- tom is the amblyopia of the hypertropic eye. In recent or low- grade vertical deviations, especially if they are alternating, even corrected vision will be compromised to some extent in both eyes, although more decidedly so in the affected eye. In old cases the fixing eye will nearly always present a close approach to normal vision (corrected if necessary) while the vision of the other eye is often lowered to a remarkable degree. The mooted question as to whether the amblyopia produces the deviation or the deviation the amblyopia is discussed under the chapters on Esotropia and Exotropia. Aside from the deviation and the amblyopia, there is no symptom worthy of note unless HYPERTROPIA. 199 it be the peculiar ''wall-eyed" appearance of such patients, especially if the hypertropia be alternating, giving to the patient the well-known hyperphoric or hypertropic "stare." Partial ptosis not ascribable to other cause is regarded by some authorities as symptomatic of hypertropia. Diagnosis. — The presence of this anomaly is easily detected, and in most cases its character and the eye to which it belongs can be determined almost at a glance. In the alternating variety resort must frequently be had to the cover-test to learn which eye fixes by preference. This test will be productive of the best results if carried out in a half-darkened room, using a small gas- flame or some other luminous point as the fixation object. By interposing a weak prism before the higher eye with the apex of the prism placed in the direction in which the eye deviates, and in- creasing it in strength until the eyes no longer move visibly when the cover is carried from one to the other eye, the deviation may be measured with a reasonable degree of accuracy. This method is applicable also to those cases in which the patient cannot be made conscious of diplopia, and it enjoys the additional advantage of being an objective method, thus rendering ^^ the surgeon entirely independent of the patient's testimony. In cases that are, or can be made, conscious of diplopia, the use of the cobalt glass before the sound eye is of great value, and all that will be necessary is to find a prism that brings the two images to a hori- zontal level. The Maddox rod is employed by some surgeons in the diagnosis of hypertropia, but its use is largely restricted to the estimation of deviation tendencies rather than to actual deviations. In all cases of hypertropia, search should be made in the extreme upper periphery of the binocular fixation field for diplopia which if found generally implies paresis of one or the other superior rectus. Thus J. C, sixteen, male, diphtheria six years ago following which the left eye "took on a peculiar appearance." / ; I. 1 1 1 200 FUNCTIONAL ANOMALIES. Clinically right hypertropia of 20 degrees seemed the proper diagnosis but search for diplopia revealed it most marked in the left upper field with the left image higher (Fig. 71J. The tropo- metric rotations were R. E. up 35 degrees, down 50 degrees, nasal 55 degrees, temporal 50 degrees. L. E., up 15 degrees, down 60 degrees, nasal 50 degrees, temporal 45 degrees. Paresis of the left superior rectus was thus plainly shown with a diagnosis of paretic left hypotrop'ra.. Advancement of the left superior rectus and tenotomy of the left inferior rectus at the same sitting gave him approximate vertical balance, (left hyperphoria of 2 degrees). Treatment. — The treatment of the varieties of hypertropia under consideration is orthoptic and operative. .By orthoptic treatment is meant the persistent use of a full cycloplegic correction of any ametropia that may be present. The effect of such lenses will frequently be much enhanced by continuing the effect of the atropin or other cycloplegic for from eight to twelve weeks, in the hope of thus re-establishing proper relations be- tween accommodation and convergence. In young subjects (under ten or twelve years) these measures will frequently lessen the devia- tion and sometimes dissipate it altogether. Tig -2— TvDical ^^tener, however, and in subjects over twelve left hypertropia. years of age in particular, a considerable devia- tion remains, which must be met by some oper- ative procedure (Fig. 72). The laws governing operative interference in heterophoria are here in force. Overaction hypertropias, mainly those found with esotropia (including anatropia) demand tenotomy of the overacting muscle or muscles of the higher eye to be combined in some cases with tenotomy of the associated muscle or muscles of the sound eye. Underaction hypertropias (usually hyperexotropias or exceptionally katatrop- ias) will be best met by advancement or muscle-shortening of the faulty muscle or muscles of the lower eye, and, where this is in- sufficient, by a similar procedure on the muscle at fault in the HYPERTROPIA. 201 fellow eye. It is to be remembered thai division of the superior rectus acts by association on the levator palpebrae superioris, and is followed, not only by depression of the cornea, but also by lifting of the upper lid, in consequence of which a considerable amount of sclera will be exposed above the cornea. However, this fact may be utilized in cases of partial ptosis, both to aid the elevator of the lid as well as the depressor of the cornea. It is further to be borne in mind that operations on hypertropes over twelve years of age are frequently cosmetic operations pure and simple; and, notwithstanding Stevens' claim that restoration of binocular vision should be the ultimate aim in these cases, such termination of them is rare and must be viewed only as a most fortunate circumstance. Finally, operative treatment is contra-indicated in hypertropia of variable degree; or of recent origin and progressive; in paretic cases of central nervous origin; and in rheumatic or gouty in- dividuals well on toward liftv vears of asre. PART IV. OPERATIONS ANESTHESIA, In heterophoria, the success of the operation depending on a partial or accurately measured tenotomy, local anesthesia is essential. Indeed, a precise operation cannot be performed unless the patient is conscious and can advise during the procedure of the effect obtained by the various steps. In heterotropia (or true strabismus) general anesthesia will be frequently necessary. Operations for convergent strabismus are oftenest done on children under twelve years of age and there are few children who are stoical enough to bear the procedure under local anesthesia whether the operation be tenotomy or advance- ment. This is always a disadvantage in that the normal co- ordinations are set aside by the general anesthetic and the eyes drift outward and upward into the position normally assumed during sleep. Under these circumstances one can form no judg- ment as to the amount of surgical correction necessary, and will have to be guided entirely by previous experiences as to how much to tenotomize, how much tissue to remove, or how far to advance a tendon in a given case. In adults many operations (even advancement) may be done under local anesthesia, especially if conjunctival and subcon- junctival anesthesia are combined. Ordinary conjunctival anesthesia is obtained by instilling one or two drops of whatever anesthetic may be used every three minutes for five applications. This will suffice in all tenotomies done without the strabismus hook and in some done with the hook. In the latter method, however, the patient often complains of much discomfort when the muscle is lifted on the hook. In- deed it is the most trying period in the operation. We have found that the use of an anesthetic subconjunctivally after con- 205 2o6 OPERATIONS. junctival anesthesia .has been produced contributes greatly to the patient's comfort. The following solution is used: 4 per cent. sol. cocaine muriate, i fluiddram. Normal saline solution, i fluiddram. Solution adrenalin, i : 2000, i fluiddram. of which 5 to 8 minims are injected with a hypodermic needle under the conjunctiva over the muscle or muscles to be attacked. During the ten minutes wait for this solution to act, gentle con- tinuous pressure is made on the eye wth a gauze pad to so diffuse the introduced liquid that it will affect the widest possible area and also to disturb as little as possible the natural topography of the parts. The operation may then be approached with fullest confidence and with a comparatively bloodless field because of the adrenalin preparation. In many adults, if they have any pluck at all, advancements may be done almost painlessly by this method. The advantage of having the patient conscious with the normal innervation to the eye-muscles during such an operation cannot be overestimated. Without subconjunctival anesthesia, relatively few advancements can be performed even on the most phlegmatic adults. Naturally other anesthetics such as holocain hydrochloride, novocain, alypin, stovaine, or beta eucain may be employed, but some adrenalin preparation should be used with them whether the anesthesia be conjunctival or subconjunctival. We have used beta eucain with much satis- faction. It cannot be too much emphasized however, that in children under twelve to thirteen general anesthesia will almost invariably be required. ANTISEPSIS. ASEPSIS AND INSTRUMENTS. The operator's hands and nails should be scrubbed with warm water and soap until all mechanical impediments to the ac- tion of the chemical agent to be used immediately afterward are completely removed. The hands are then dipped in a solu- tion of bichlorid, biniodid, or cyanid, of mercury, i to 3000. The skin of the patient's face in the neighborhood of the eye is scrubbed TENOTOMY. 207 with warm water and soap, then douched with normal salt solu- tion, and washed finally with i:6ooo mercurial solution. In this manipulation, particular attention must be paid to thorough cleansing of the eyebrows and lashes. The conjunctival sac and the conjunctival surfaces of the lids are flushed with physiologic salt or saturated boric-acid soluton, and fresh cocain solution is applied. The instruments are first placed in boiling water and then in alcohol, where they are allowed to remain until used. This simple method of treating the instruments is sufficiently germicidal for all operations where the field is not unusually septic. TENOTOMY. The object of tenotomy is two-fold: By altering the tendinous attachment of a muscle to change its mechanical relations to the globe and to the other muscles, and by thus lessening the power of the muscle to so influence the distal response to innervation, that equilibrium and coordination shall be inaugurated or re- established; second, to develop or restore symmetric and corre- sponding nerve-excitation. We are concerned, first, with the muscle or muscles at fault, and, second, with the degree of devia- tion — i. e., whether there shall be partial or complete muscle- division, and whether it shall apply to one or both eyes. In heterophoria, unless there is good ground for believing that one muscle is abnormal either in structure or insertion, the operation should in all cases be divided between the two muscles, relieving an equal amount of tension in each. In heterotropia (esotropia for instance) the evils resulting from extensive tenotomy in one eye for high grade deviation are limited movement nasalward, diplopia in the periphery of the field, cicatrization of the con- junctiva and capsule at the site of the wound, retraction of the caruncle and protrusion of the eyeball. In monolateral strabismus with high grade amblyopia it is our practice to do a moderate tenotomy of the internus and extensive advancement of the externus of the deviating eye. Later, if necessary, advancement may be done on the externus of the sound eye. The same 208 OPERATIONS. principles obtain in exotropia, save that the muscles to be attacked are of course reversed. In esotropia or exotropia without well marked amblyopia, advancement of both externi or interni (as the case may be) is the operative procedure of election. Fig. 73. — Instruments used in tenotomy, a, scissors; b and c, tenotomy hooks; d, speculum; e, conjunctival forceps. After insertion of the speculum or separation of the lids by an as- sistant (lid elevator held in one hand and the lower lid depressed by a linger of the other hand) the conjunctiva and the capsule lying immediately over the insertion of the tendon into the sclera are firmly grasped by the single tooth conjunctival forceps. TENOTOMY. 209 Considerable pressure with the forceps at right angles to the ball is necessary to ensure the embrace of the capsule with the mucous membrane. The advantage of securing both can be appreciated in the next step, the incision. If both structures can be divided and the tendon exposed at its insertion by one snip of the scissors, this part of the operation is considerably simplified. Two slight difficulties present themselves in case the conjunctiva alone has been divided; the smooth surface of the capsule uncovered by mucous membrane and made tense by out- ward rotation of the cornea, is slip- pery and hard to grasp; and again, unless one is cautious he is apt to include the tendon in the grasp of the forceps and to divide it uninten- tionally. The incision should not exceed the width of the tendon; if the desired result is not obtained it may be widened at the close of the opera- tion; if it be too narrow, the neces- sary manipulations are hindered (Fig. 74). A few operators prefer to make the direction of the incision horizontal, parallel and close to the lower border of the tendon, but the common practice, and the better one, is to make it vertical in order that it may have the greater influence in the regulation of the final result. Having exposed the tendon at its attachment, a small hook is passed under its entire width from above or below, the distal end of the hook com- ing into view at the upper or lower extremity of the incision, using the scissors to snip away any capsular folds that the hook is likely to push before it. The tendon may now be divided to any extent desired (see Fig. 74) . The method recommended for the correction of heterophoria is to incise first the middle fibers and then if necessary divide toward the marginal, according to the degree of effect previously determined, gauging the progress toward equilibrium by frequent interruptions of the operations for exam- 14 Fig. 74. — Showing size of verti cal conjunctival incision also tendon about to be divided. 2IO OPERATIONS. ination by the tests above described. In heterotropia, the divi- sion of the operation into these stages is less important since the tendon is to be detached in almost its entire width. If section of the tendon alone vi^ill not restore equilibrium, the conjunctival wound can be enlarged and the fibers radiating from the upper and lower margins of the tendon and from the capsule of Tenon can also be severed, but care must be exercised that the evil effects of too extensive division of the capsular attachments already alluded to shall be avoided. The value in prism degrees, of section of the tendon varies in different cases from 2 to 10 degrees or more. In graduated tenotomy — i. e., division of a few fibers in the center of the tendon, or of both margins the effect is decidedly limited (see Fig. 53); when the whole tendon is severed, without addi- tional incisions of the conjunctiva or capsule, the effect would average about 8 degrees. In proportion to the tissues divided and the extent of the wound the effect may vary from slight weakening of the muscle to a practical paralysis. Union of the tendon to the sclera may take place so far back that the muscle loses all power of rotating the cornea, or, indeed, it may always remain detached. Perhaps our figures as to the effect secured may seem small, but they are the result of an experience numbering several hundred tenotomies and they are, we believe, as correct as general averages usually are. Tenotomy or advancement of the superior or inferior recti may be performed after the same principles as the same opera- tions on the lateral muscles. The operator should bear in mind the relative less power of the vertical than the horizontal and consequently confine his operations within narrower limits. Since the defect requiring operation is proportionately less (almost one-third), the' effect of complete tenotomy or extensive advancement or resection, is almost prohibitive of subsequent binocular fixation in all portions of the field. Operations on the oblique muscles are rarely indicated. The effect of such operations may be more accurately obtained by opera- tions on a lateral combined with an operation on a vertical muscle. The after-treatment is simple. Cold applications for a few TENOTOMY. 211 hours and frequent instillations of saturated boric-acid solution are all that are necessary in the majority of cases. A bandage is seldom used; on the contrary, it may be positively harmful in that, in the exclusion of binocular fixation, the important factor to success, namely, the unconscious effort at fusion, is prohibited. If immediately, or a c^iy or two after operation, the defect is found to have been over-corrected, a suture to either close the conjunctival wound or a deeper one that shall include the cap- sule and the severed muscle may be inserted. It is the practice of some operators to introduce the suture before cutting the muscle, so that an over-defect may be instantly neutralized; but this is, we believe, an unnecessary precaution for a skilful operator. Accidents. — It occasionally happens, through an anomalous distribution of the large vessels, that one of them is torn or cut, producing immoderate hemorrhage. This is especially true of the vertical muscles. In this unfortunate event the operation should be suspended and a pressure bandage applied. A second accident is the unexpected perforation of the sclera by the scissors while cutting the tendon, which must be ascribed to using too sharp-pointed scissors or to cutting with the ends of probe- pointed ones at right angles to the tendon (instead of on a line with the muscle), with undue force. The operation must be at once discontinued, the conjunctiva sutured over the perforation, and a pressure bandage applied. Healing. — After the usual operation, the tendon re-attaches to the sclera in from three to four days. If the wound should become infected, tenonitis, orbital phlegmon, ulceration of the sclera or cornea, or panophthalmitis may ensue. Tenotomy has been known to be the exciting cause, also, of detachment of the retina, essential phthisis, and hemorrhage fatal to the sight and to the integrity of the ball. Disappointment as to Result. — A perfectly performed tenotomy will sometimes fail to favorably affect the deviation for which it was undertaken, in which event it is not unlikely that the failure can be ascribed to some anomalous arrangement of the check liga- ments which accompany the recti muscles. (See Figs. 4, 5, and 6.) ADVANCEMENT OR RESECTION. As has been said in the chapter on Tenotomy, local anesthesia (by combined conjunctival and subconjunctival anesthesia) should be employed whenever feasible in all advancement or resection operations. In children under fourteen, general anesthesia is imperative and nothing but experience will guide Fig. 75. — Instruments used in advancement or resection operations, a, scissors; h and c, strabismus hooks; d, speculum; e, conjunctival forceps; /, needle holder; g. Prince's clamp or advancement forceps. the operator under these circumstances in the amount of tissue to be excised or the distance a tendon is to be advanced. Numerous operations for increasing the efficiency of any one muscle have been advocated. Their number points to the inadequacy of any single procedure. The object may be accom- ADVANCEMENT OR RESECTION. 213 plished either by advancement of a muscle or tendon, or by resection — or cutting out of a piece of a tendon or muscle. Natu- rally each of these methods has its supporters. It seems to us wise to omit the description of the great majority and to confine ourselves to those which have proved most efficient in our hands. Fig. 75 shows the necessary instruments. The principal objection to be urged against most advancement operations is, that the sutures by which the advanced tendon is attached to the conjunctiva frequently tear out, allowing the tendon to recede to a point farther back on the ball than that to which it was formerly attached, and the original deviation is thus aggravated. The advantage of resection or shortening a muscle is that there is no danger of increasing the deformity since the tendon, at its attachment to the sclera, is not disturbed and the shortening process is confined to the muscle and tendon. When small effects are desired our preference is for an opera- tion that is a modification of the tendon folding of LaGleyze. Excepting instances of marked deformity, in which the purpose of operation is mainly cosmetic, this measure aft'ords satisfactory results in many cases. Its efTect can be accurately gauged; it is absolutely without danger of increasing the original deformity; it is attended with but moderate traumatism, and the healing is, as a rule, uneventful and rapid. First Step. — After anesthetization the conjunctiva is grasped with the forceps over the inferior corner of the tendon-insertion and divided vertically 4 to 5 mm., and (starting at the same point) horizontally along the lower border of the muscle as far back as is necessary to given a roomy field for operation. The subconjunctival tissue and the capsule of Tenon are similarly treated, the structures thus far divided forming a flap, which is turned upward (Fig. 76). Fig. 76. — Exposure of the muscle. 214 OPERATIONS. The Second Step. — The muscle is now brought plainly into view by the strabismus hook and freed from all adhesions, when a black silk thread, armed at each end with a fine curved needle, is introduced into the substance of the muscle from 6 to 8 mm. back of its insertion, one needle passing through the upper border of the muscle from its conjunctival to its scleral surface, the other through the lower border in like manner, and the thread drawn taut over those fibers included between the two points of entrance of the needles. Third Step. — The needle belonging to the upper portion of the muscle suture is now passed under the tendon at the upper border Fig. 77. — Introduction of sutures. Fig. 78. — Tying of sutures, pro- ducing knuckle in muscle. of its insertion and brought out near the center of the con- junctival surface of the attachment; the second needle, belonging to the lower portion of the muscle suture, is introduced in exactly the same manner under the lower border of the tendon-insertion and brought out on the conjunctival surface just below the first needle (Fig. 77). An assistant now grasps the muscle back of the point where the needles were first introduced and brings the muscle forward, when the suture is drawn tight and tied, by this measure advancing the whole muscle nearly as far as the tendinous attach- ment and producing a fold or hump in the muscle (Fig. 78). The summit of this muscular fold or hump is then cut away, leaving the upper and lower borders intact and the two raw ADVANCEMENT OR RESECTION. 215 surfaces in juxtaposition (Fig. 79). The suture is cut off so that its ends may protrude a short distance through the conjunctival wound, which is now brought together by two sutures (Fig. 80) or more sutures in each side. Pain in the healing may be largely prevented by the constant application of ice-water compresses and frequent instillations of a solution of boric acid and cocain. The conjunctival threads may be removed in a few days, and the thread in the muscle should be allowed to remain as long as it causes no irritation. Any difficulty that might be experienced in the removal of this deep thread can be forestalled by leaving long ends to it, so that it may be readily brought away by the forceps. if Fig. 79. — Knuckle cut oflf leaving ends approximated. Fig. 80. — Finished eiTect after tj'ing of conjunctival sutures. Capsular Advancement. — Another method of correcting the smaller deviations is to advance the capsule of Tenon, as recom- mended by de Wecker.^ It consists essentially in incising the conjunctiva freely in the vertical meridian about 4 to 6 mm. from the cornea; then, grasping the capsule over the insertion of the muscle at fault, sutures are made to take firm hold on the capsule and the free ends are carried under the conjunctiva, one above and the other below, as far as the middle of the cornea. These sutures are then tied with careful attention to the traction they produce on the advanced capsule, so that the tension will be equal above and below. This operation, known as capsular advancement, ^ De Wecker and Masselon, Man. (TOphthal., Vol. II, p. 778. 2l6 OPERATIONS. is indicated only in the smallest degrees of heterophoria, and is of no value in well-established squint. For larger and cosmetic effects in the grosser deviations some such operation as Wootten's or Worth's is our preference. Worth proceeds by incising the conjunctiva and capsule verti- cally (Fig. 8i, i), and then bringing the muscle plainly into view on the strabismus hook (Fig. 8i, 2), when it is freed from all attach- ment for a distance of almost 8 to 10 mm. from its insertion. At this point Prince's advancement forceps are introduced (Fig. 81, 3) and made to clamp between its blades the conjunctiva, capsule and muscle, the upper blade of the forceps resting on the external surface of the conjunctiva, the lower one on the sclera. (It will thus be seen that in this operation a resection is done of all the tissues including the conjunctiva, capsule and muscle). The sutures are now introduced. Beginning within and near the upper border of the muscle, a needle is carried from without inward 3 to 4 mm., back of the blade of the forceps through all the structures (Fig. 81, 4). On emerging on the scleral side the needle is immediately reversed in the needle holder and carried back parallel to the way it was brought forward, but just above the upper border of the muscle, coming out through the capsule and conjunctiva (but not including the muscle (Fig. 81, 5). The suture is then tied down on the ex- ternal surface of the conjunctiva and thus secures in its grasp a few fibers of the muscle. A separate suture armed again with one needle is introduced similarly at the lower border of the muscle, being carried in and out in the identical manner and then tied (Fig. 81, 6). The tendon is now severed from its main attachment and all line fibrous subsidiary attach- ments dissected away. Turning back the muscle and its accom- panying structures on the Prince's forceps, the needle belonging to the upper suture is again passed through all the structures, being introduced i mm. directly back of the knot previously made and the suture is carried forward and anchored firmly at the original site of insertion of the tendon, care being taken to get a good bite in the episcleral tissues with the needle before the suture is drawn ADVANCEMENT OR RESECTION. 217 Fig. 81.— Diagrammatic representation of Worth's operation. 2l8 OPERATIONS. through. The same step is now taken with the lower suture (The object of bunching up the muscular fibers in each suture as first tied is to afford the traction suture inserted behind it something definite to pull on without the danger of pulling out through the muscular fibers, a post-operative ac- cident that occurs none too infrequently). The next step is to excise the portion of the tissues held in the grasp of the Prince's forceps by cutting with the scissors between the forceps and the knots adjoining the traction sutures when quite a portion of the sclera is exposed (Fig. 8i, 7). The final step of the opera- tion is to tie firmly together the two ends of the suture aa' and then similarly tie down firmly the two ends of the suture hb', which should result in good approximation of the cut end of the muscle to the original site of insertion of the tendon (Fig. 81,8). If there is any gaping at the center of the approximated structures it is good practice to introduce a third suture to facilitate smooth healing and afford additional support to the previously introduced traction sutures. It is difficult to say in arbitrary terms just how much tissue is to be excised, but under ordinary circumstances removal of a 3 mm. wide strip produces a satis- factory result. When it is decided to do tenotomy and resec- tion at the same time on one eye, it is best to perform the tenotomy just before the final tying is done with the advancing sutures in the resection operation. This enables the surgeon to get the fullest effect out of the resection operation. One marked advantage of the operation just described is that all the knots are tied in the external surface of the conjunctiva, so that when they are to be released and removed no difficulty whatever is experienced. When advancement or resection operations are done on one eye only {under local anesthesia), the patient may sometimes be allowed to go home immediately afterward if the operation has been done under local anesthesia. He should be cautioned to remain per- fectly quiet at home for two days with the eye or eyes bandaged. Any advancement operations done under general anesthesia whether upon one or both eyes require that the patient should ADVANCEMENT OR RESECTION. 219 remain in bed for forty-eight hours with one or both eyes bandaged (as the case may be) throughout that time. If at the end of forty- eight hours the position of the eye is satisfactory to the surgeon the bandage should be reapplied for twenty-four hours longer — but if the effect seems too great the bandage may be removed in the hope that the antogonistic muscle may help to stretch the tissues during healing. Wootton's operation is somewhat similar to the one just de- scribed, differing mainly in the method of introducing the sutures which will be seen at a glance in referring to Fig. 82. There is the possibility, however, that the sutures may pull forward and out through the fibers of the muscle in this operation as in the modi- fication of the LaGleyze operation above described. Valude, Sydney Stephenson, Verhoeff, Briggs, Reese, Vard Hulen and many others have offered advance- ment or resection operations that differ from the above operations in one or another detail, but we have found the one fully described of the greatest service and to it we pin our faith. After-Treatment. — After the operation is completed 20 per cent, argyrol solution should be instilled and both eyes bandaged, with the object of preventing infection in- ducing rapid healing, and, by re- moving any stimulus to movements of the eye, prevent tearing out of the threads. The inclusion of the unoperated eye in the bandage is important even though only one eye has been operated upon, for by this means only will the eyes be kept still. Twenty- four or forty-eight hours later the bandage may be removed, the face washed with bichloride solution, the crusts on the lashes dissolved and the conjunctival sac washed out with boric acid solution. Instillation of a few drops of argyrol (20 per cent. Fig. 82. 2 20 OPERATIONS. solution) is recommended before the bandage is reapplied. In monocular operation the bandage may be omitted after forty- eight hours; in binocular it should be continued for twenty- four hours longer. The postoperative reaction usually subsides in from one to two weeks, although the eyes may remain congested for several weeks. Speaking generally, the sutures may be removed (under cocaine anesthesia) at the end of a fortnight INDEX. Abducens palsy, diagram of, 52 Abduction, 100, 103, 109 Action of prism on beam of light, 80 Accommodation, 82 Adduction, 100 103, 104, 108 Advancement, 212 * after treatment, 218, 219 bandaging after, 218 capsular, De Wecker's, 215 instruments for, 212 modification of La Gleyze's opera- tion, 213 operations, objection to, 213 postoperative reaction, 220 Wootton's operation, 219 Worth's operation, 216 Anesthesia, 205 subconjunctival, 206 Anesthetic solutions, isotonic, 206 Anesthetics used in muscular operations, 206 Amblyoscope, Worth's, 34 AmpHtude of convergence, 106 Anaphoria, 113 Anatropia, 113, 196 Antagonistic muscles, 30 Antisepsis, 206 Arc rotations, 109 Asepsis, 206 Average arc rotations, 21 Axiom concerning prisms, 81 Bar reading, 38 Binocular vision, 23 evolution of, 34 Johnson's scheme, 35 tests for, 37 Capsule of Tenon, 8 Cataphoria, 113 Catatropia, 113 Check, ligaments, 10 Clinoscope, Steven's, 112 2 Conjugate innervations, 30 Conjunctival anesthesia, 205 Convergence, amplitude of, 106 concerning, 85 near point, 107 Corresponding or identical points, 23 Cortical centers of the muscles, 17, 18, 19 Cyclophoria, 80 Decentering lenses, 157 Jackson's table for, 158 Diaphragm test, Harman's, 39 Diplopia, 48 Diploscope, Remy's, 38 Double prism, Maddox, 91 Douziemeter, 161 Duction power, measure of, 103 Ductions or prism rotations, 100 Esophoria, 79, 114 advancement in, 122 convergence repression in, 117 etiology, 115 operation in, 121 partial tenotomy in, 125 prism exercise in, 118 rest prisms in, 119 sedatives in, 118 symptoms of, 114 tenotomy in, 122 treatment of, 117 various methods of tenotomy in, 125 Esotropia, 165 alternating, 180 advancement in, 183 diagnosis of, 180 etiology of, 180 operation in, 182 tenotomy in, 183 treatment of, 182 amblyopia in, 171 bar reading in, 183 cover test in, 172 diploscope in, 185 Harman's diaphragm test in, 185 due to congenital paresis of external recti, 167 etiolog}' of, 165 » full corrections in, 177 fusion faculty in, 165, 166 monocular, 170 advancement in, 179 diagnosis, 170 221 222 INDEX. Esotropia, measurement of deviation,i72 monocular tenotomy in, 179 treatment of, 176 perimeter estimate of deviation, 173 Priestley Smith's method of measur- ing, 174 refraction errors and, 165 relation to obstetrical injuries, 167 to vertical deviation, 179 stereoscope in, 183 tape method measurement, 174 tropometer in, 176 Worth's amblyoscope in, 178 Exophoria, 79, 126 advancement in, 140 amplitude of convergence in, 131 and cycloplegics, 132 classification, 126 convergence training in, 134 diagnosis of, 128 etiology of, 127 nerve tonics in, 132 operation in, 139 prisms in, 136 prism exercises in, 134 for reading distance, 138 supplementary tests, 131 symptoms in, 127 tenotomy in, 139 treatment, 132 Exotropia, 186 advancement in, 193 classification of, 186 diagnosis of, 189 etiolog}' of, 187 operation in, 193 tenotomy in, 193 treatment of, 191 symptoms of, 188 Fascia, orbital, 3 Field of fixation, binocular, in monocular, in Gould's prism battery, 100 Hering's test box, 37 Heterophoria, 75, 79 Cobalt's glass test, 92 convex spherical test, 93 diagnosis of, 88 diplopia or displacement tests, 88 distorting tests, 94 etiology of, 78 Graefe's diplopia test, 89 Maddox's rod test, 94 position of streak in Maddox's rod test, 95 tests for the reading distance, 97 Heterophoria, the cover test, 96 the parallax test, 96 Heterotropia, 164 Hyperexophoria, 79 Hyper kinesis, 80 Hyperphoria, 79, 141 diagnosis of, 145 due to central disease, 156 etiology of, 144 operation in, 156 optometer in, 145 paretic, 149 relation to lateral deviations, 150 rest prisms in, 153, 154 treatment of, 152 tropometer in, 153 spurious, 142 statistics of, 141 symptoms of, 142 Hypertropia, 195 advancement in, 200 diagnosis of, 199 etiology of, 195 operation in, 200 organic, 197 symptoms of, 198 tenotomy in, 200 tropometer in, 200 and esotropia, 196 Hypoesophoria, 79 Hypoexophoria, 79 Hypokinesis, 80 Hypophoria, 79 Infraduction, 100, 103 Innervation of the muscles, 17 Insertions of muscles, 7 Instruments, preparation of, 207 Jackson's table for decentering, 158 Law of corresponding points, 24 of direction, 22 of projection, 21 Lenses, decentering of, 157 prismatic testing of, 159 Levator palpebrre, 7 Maddox's prism test for reading dis- tance, 98 rod, simple, 94 compound, 94 test for reading distance, 98 Muscles, 3, 4 Muscular balance, 76 imbalance, diagnosis of, 88 distorting tests, 94 Musculo-dynamics, 98, 108 INDEX. 223 Nerve supply of musclei, 12 Nomenclature of muscular anomalies, 79 Nuclear centers, 18 Nystagmus, 70 Object test card, Reber's, 170 Oblique inferior, 7 superior, 6 Ocular palsies, 43 diagnosis, 45 etiology, 43 oculomotor, 52 primary deviation, 47 symptomatology, 46 Operations, 201 Ophthalmo-dynamometer, Landolt's, 106 Ophthalmoplegia, externa chronica, 45 interna recurring, 55 Orthophoria, 79 Palsies, conjugate, 64 ocular, diagnosis, 49 diagram of images in, 57, 59 diplopia in, 48 electricity in, 69 false projection, 47 Maddox's rod in, 52 operation in, 70 primar)' deviation, 47 prognosis in, 66 secondary deviation, 47 strychnin in, 69 symptomatology', 46 treatment, 67 vertigo in, 48 vicarious rotations, 48 Palsy, abducens, diagram of, 52 conjugate vertical, 65 convergence, 64 external rectus, 6r inferior oblique, 58 rectus, 58 internal rectus, 55 recurrent oculomotor, 53 superior oblique, 58 rectus, 56 Phorometer, hand, Well's, 102 Steven's, 89 Physiologic diplopia, 24 Position of rest, 76 Predominant action of muscles, 20 Primar}' posirion, 20 Prisms, concerning, 80 Prism, convergence, 100 deorsumvergence, 100 divergence, 100 Measure card, Ziegler's, 160 Prism, rotations or ductions, 100 sursumvergence, 100 Prismatic lenses, testing of, 159 Ptosis, 44 acquired, 45 Range of convergence, 106 Ratio between abduction and adduc- tion, 109 Reber's object test card, 170 Rectus externus, 5 inferior, 6 internus, 5 superior, 5 Relation between accommodation and convergence, 82 Resection operations, 212 Risley's rotary prism, 10 1 Rotarj' prism, Risley's, loi Rotation of the muscles, 20 Scheme illustrating accommodation and convergence at different dis- tances, 84 associated muscles, 28, 29 of the dominant action of the muscles, 26 of the third nerve nucleus, 13 Spasm of the ocular muscles, 70 Spiral of insertions, 7 Stereoscope, Brewster's, 32 Holmes, 33 Javal, 33 Wheatstone's, 32 Supraduction, 100, 103 Synergistic muscles, 26 Tenotomy, 207 accidents of, 2 1 r after treatment, 210 effect gained by, 210 healing after, 2 1 1 inferior rectus, 210 instruments for, 208 partial, 210 superior rectus, 210 technic of, 207 Theorv- of innervation, 19 of the stereoscope, 31 Torsion, Maddox's rod in, 52 Tropometer, average arc rotations, no scale for, in Steven's, 109, no Vascular supply of the nerve nuclei, 13 of the muscles, 15 Venous supply of the muscles, 16 Ziegler's prism measure card, 160 14 DAY USE RETURN TO DESK FROM WHICH BORROWEl on the date to which renewed. 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