THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES fr< Y^^^ / ^, 2), AFTER FOLLIN. RECENT ADVANCES OPHTHALMIC SCIENCE. THE BOYLSTON PEIZE ESSAY FOR 1865. HENRY W. WILLIAMS, M. D., OPHTHALMIC SURGEON TO THE CITY HOSPITAL, BOSTON ; UNIVERSITY LECTDRER ON OPHTHALMIC SDRGERY IN HARVARD DNIVERSITY ; MEMBER OF THE AMERICAN OPHTHALMOLOGICAL SOCIETY j ETC., ETC., ETC. "Nimia oculi longitudo facit myopiatn." — Boerhaave. ^irijjti ^ BOSTON: TICK NOR ANT> FIELDS. 1866. Enterert according to Act of Congress, in the year 1866, I>y IIKXHY W. WILLIAMS, in the Clerk's Office of the District Court of the District of Massacliusetts. University Press : Welch, Bicelow, & Co., Camrridge. The Boylston Medical Committee, appointed by the President and Fellows of Harvard University, consists of the following physicians : — Edw. Reynolds, M. D., John Jeffries, M. D., S. D. TOWNSEND, M. D., J. B. S. Jackson, M. D., J. Mason Warren, M. D., D. H. Storer, M. D., Chas. G. Putnam, M. D., Morrill Wyman, M. D., Henry J. Bigelow, M. D. At the Annual Meeting, held June 1, 1865, the Premium was awarded to Henry W. Williams. M. D., for the best Dissertation on Recent Afh iHinces in Ophthalmic Science, bearing the motto : " Nimia oculi longitudo facit myopiam." By an order adopted in 1826, the Secretary was directed to publish annually the following votes : — 1st. That the Board do not consider themselves as approving the doc- trines contained in any of the dissertations to which premiums may be adjudged. . 2d. That in case of publication of a successful Dissertation, the author be considered as bound to print the above vote in connection therewitli. J. MASON WARREN, Secretary. • PREFACE. This essay, to which was awarded the Boylston Prize, offered by Harvard University for the best dissertation on " Recent Advances in Ophthalmic iSci- ence^^^ is not devoid of the faults incident to such a treatise, which, from the nature of the question proposed, embraces a variety of subjects, but ought not to exceed moderate hmits. It is hoped, however, that it may in a measure sup- ply the demand, wdiich becomes every day more ur- gent, for a work which, without being too elaborate, may assist the student and the general practitioner in acquiring a knowledge of the principles of the Oplithal- moscope and of its practical application, — and which may also elucidate, so far as is possible in a brief resume, other important points in regard to wdiich im- mense progress has been made within a few years, leading to a more correct understanding of the optical powers and functions of the eye, and of the results of aberrations from the normal standard. VI PREFACE. I have endeavored, without introducing the nice- ties of abstruse mathematical calcuhitions, to give a concise and clear exposition of the manv new facts and principles, of which the recent demonstration, by Professors Donders, Graefe, Helmholz, and others, has conferred a fresh lustre upon Ophthalmology, and' entitled it to a high place among the depart- ments of medical science. I am indebted to the accurate scientific knowledge and artistic skill of my friend, Dr. John Green, for drawings of the plates which so greatly enhance the value of the work ; and I think it Avill be admitted that these illustrations, — especially those explaining the Ophthalmoscope, and those which relate to the functions of the eye in refraction and accommoda- tion, — afford to. the no\ice in these studies a more perfect demonstration of the principles involved, and of their application, than can be found in any work which has hitherto appeared. 15 AuLiNGTox Strket, Bostox, 1st January, 18GG. TABLE or CONTENTS. THE OPHTHALMOSCOPE. Invention of Helmholz, 5. — Direct Method of Examination, 7, 15. — Con- cave Mirror, 8. — Indirect Exatnination, 9, 16. — Principle of Construc- tion, 9. — Use of Object-Glass in indirect Jlethod, 9. — Use of Eyeglass behind the Mirror, 12, 17. — Mode of using, 14. — Binocular, 19. — Ap- pearances to be observed with, 22. — Advantages of, 25. LATERAL ILLUMINATION. Mode of employing, 26. — Advantages of, 26. OPTOMETERS. Principle and Construction of, 27. TEST LETTERS. As a Standard to determine Acuteness and Range of Vision, 28. LIMITATION OF THE FIELD OF A'ISION. Modes of determining, 30. ACCOMMODATION OF THE EYE TO DISTANCES. Apparatus for demonstrating, .32. NEW THERAPEUTIC AGENTS. Calabar Bean, 33. ANESTHETICS. Their Use in Operations on the Eye, .35. — In Cataract Operations, 36. TENSION OF THE EYEBALL. Mode of detecting and estimating, 38. PARACENTESIS OF THE CORNEA. As a Relief for internal Inflammation, 40. Vlll TABLE OF CONTENTS. IREDECTOMY. Mode of performing, 42. — Slight Risk attending it, 44. IRIDDESIS. Cases for wliich it is adapted, 44. — Mode of doing, 45. CORELYSia Method of separating Adhesions of the Iris, 46. DISEASES OF THE EYE ORIGINATING IN MORBID CONDITIONS OF THE SYSTEM. Exophthahnos, 48. — Hemeralopia, 49. — Briglit's Disease, 51. — Cataract in Diabetes, 52. — Sequelae of Diphtheria, 52. — Inherited Syphilis, 53. — Infantile Sj'philitic Iritis, 54. — Syphilitic Keratitis, 55. — Deformities of Teeth in Syphilitic Keratitis, 57. — Syphilitic Disease of the Retina in Adults, 58. SYMPATHETIC INFLAMMATION OF THE EYE. Cases where it is liable to occur, 60. — Often seen after a considerable Interval, where one Eye has been injured, 60. — Early Symptoms, 61. — Treatment, 61. ENUCLEATION OF THE EYEBALL. Mode of performing, 63. — Speedy Recovery, 63. GLAUCOMA. Predisposing Causes, 64. — Usually affects both E3'es, 65. — Early Symp- toms, 65. — Chronic Form, 65. — Acute Form, 66. — Ophthalmoscopic Appearances, 67. — Hardness of Globe, 67. -^ Pathological Changes in advanced Stage, 68. — Theory of, 69. — Treatment by Iridectomy, 70. — Prognosis, 70. — Recovery not impossible when even Perception of Light has been lost, 70. — Danger of delaying Operation, 70. — Relief of Pain and Improvement of Vision resulting from Iridectomy, 72. APOPLEXY OF THE RETINA. Symptoms and ophthalmoscopic Appearances, 73. HYPER^ESTHESIA OF THE RETINA. Symptoms, 74. SEPARATION OF THE RETINA. By Effusion of Serous Fluid, 75. — Appearances as seen with the naked Eye, 75. — As seen on lateral Illumination, 76. — Ophthalmoscopic Ap- pearances, 76. — As a Cousequeuce of posterior Staphyloma, 76. TABLE OF CONTENTS. ix CHOROIDITIS. Ophthalmoscopic Appearances. 77. — Implication of the vitreous Humor, 78. — Infiltration of Retina, 78. — Ketinitis Pigmentosa, 78. — Treat- meat, 79. — Iridectomj', 79. , POSTERIOR STAPHYLOMA. Occurs around Entrance of optic Nerve, 79. — A frequent Concomitant with Myopia, SO. — Ophthalmoscopic Appearances, 80. — Alterations in Macul.a Lutea, 81. — Separation of the Ketina, 81. — Increased by improper Use of Eyes, 81. — Importance of Examination with Ophthal- moscope in Cases of Myopia, 82. — Progressive Tendency during Pe- riod of Youth, 82. OPACITIES IX THE VITREOUS HUMOR. Result from Disease of contiguous Parts, 83. CATARACT. Early Diagnosis by Cleans of Ophthalmoscope and by Lateral Illumina- tion, 83. OPERATIONS FOR CATARACT. Extraction preferable to Operations for Displacement, 84. — Extraction during Anaesthesia, 84. — Out-scooping, 85. — Iridectomy preliminary to Extraction, 87. — Iridectomy simultaneously with Extraction, 88. — Linear Extraction, 88. — Extraction by Suction, 89. — Suture of the Cornea after Extraction, 90. — Advantages of immediate Union of Edges of Wound, 91. IRIDECTOMY FOR THE RELIEF OF OCCLUSION OF THE PUPIL. Its Necessity in many Instances, 92. — Relief of intra-ocular Pressure, 93. — Danger of Delay, 93. IRIDDESIS. As a Substitute in certain Cases for Iridectomy, 94. — In congenital Cat- aract, 94. — In conical Cornea, 95. STAPHYLOMA OF THE CORNEA. Excision of the Staphyloma preferable to Enucleation of the Eyeball, 98. — New Operation for, 98. DIPHTHERITIC INFLAMMATION OF THE CONJUNCTIVA. Symptoms, 100. X TABLE OF CONTENTS. THE FUNCTION OF ACCOMMODATION. Powers of a normal Eye, 102. — Range of, 103. — Seat of, in crystalline Lens, 104. — Mechanism of, 104. — Demonstration of, 106. — Auxiliary Changes in Iris, 108, — Coincident Action of Kecti Muscles, 109. — Dif- ference between Accommodative and Refractive Power, 110. — Suspen- sion of during Paralysis, or under the Influence of Atropia, 110. — Ac- commodation in the Myopic Eye, 111. — In the Hypermetropic Eye, 112. — Mode of determining Range of, 114. — Instrument for measur- ing, 117. ANOMALIES OF ACCOMMODATION. Affecting the adaptive Power, 118. PRESBYOPIA. Depends on increased Hardness of the crystalline Lens, 119. — May occur in mj'opic or hypermetropic as well as in normal Eyes, 120. — Age at which it occurs in a normal Eye, 121. — Relief by convex Glasses, 121. — Degree of, 122. — Sometimes a premonitory Symptom of Glauco- ma, 123. INSUFFICIENCY OF THE INTERNAL RECTL A Cause of Fatigue of the Ej-es, 124. PARALYSIS OF THE CILIARY MUSCLE. A frequent Consequence of exhausting Diseases, 126. — Attended by Loss of Power of Accommodation, 126. — May be artificially induced by Use of Atropia, 127. — Counteracted by Calabar Bean, 127. SPASM OF THE CILIARY MUSCLE. A Cause of indistinct Vision, 128. ANOMALIES OF REFRACTION. Causes of, 129. — Relative Form of the Myopic, Emmetropic, and Hyper- metropic Eye, 130. MYOPIA. Results from abnormal Form of Eyeball, 131. — Differences in Length of antero-posterior Diameter, 131. — Often Hereditary, 132. — Progressive Tendency, 132. — Age when it tends to become developed, 132. — Elon^ gation and Distension of the Tunics of the Eyeball, 133. — Correction by concave Glasses, 136. — Measurement of, 136. — Selection of Glasses, 140. — A Cause of Divergent Strabismus, 140. TABLE OF CONTENTS. xi IIYPERMETROPIA. Caused by a too short antero-posterior Diameter of Globe, 141. — Correc- tion by convex Glasses, 142. — Abnormal Form of Eye to be observed on Inspection, 143. — Has tio progressive Tendency, 143. — Manifest and Latent Hypermetropia, 143. — Determination of the Amount of Absolute Hypermetropia, 144. — Correction by convex Glasses, 145. — Measurement of, 145. — Range of Accommodation in, 146. — Often He- reditary, 146. — Not an abnormal Condition in advanced Age, 147. — A Cause of Convergent Strabismus, 147. ASTHENOPIA. Often depends on Hj'permetropia, 148. — Sometimes on Insufficiency of Internal Recti, 148. — Another Variety relieved by Rest and Tonics, 149. ASTIGMATISM. Caused by a Want of Symmetry of the Cornea in different Jleridians, 149. — Vision not equally good for horizontal and vertical Lines, 150. — Determination by looking through a small Slit, 151. — Relieved by cy- ■ lindrical Glasses, 151. STRABISMrS. Intimately related to the Functions of the Eye, 153. — Vision less perfect in the most affected Eye, 153. CONVERGENT STRABISMUS. Generally coexistent with Hypermetropia, 154. — Results from Efforts to increase Accommodation, 154. — Secondary Squint, 156. — Measure- ment of, 157. — Operation on both Eyes sometimes necessary, 157. — Mode of operating, 158. — Use of Glasses to correct Hypermetropia, 158. — Importance of operating early in Life, 159. DIVERGENT STRABISMUS. Depends on Myopia, in most Cases, 159. — Difficulty of rotating the Eye, 160. — One Eye alone employed for near Vision, 160. — Loss of binocu- lar Vision, 161. — Forced Inversion after Operation, 162. — Glasses after Operation, 162. RECENT ADVANCES IN OPHTHALMIC SCIENCE. Never, perhaps, in the same period of time, have so many and so brilliant advances been made, in any department of medicine, as have been attained within half a generation in the knowledge and treatment of diseases of the eye. And it is not alone as applied to the diagnosis and therapeutics of this organ that these acquisitions have their importance ; but the vast additions to our knowl- edge of morbid phenomena, as they can be watched and demonstrated in the eye, have been doubly valu- able from the information they afford us in regard to pathological processes in other parts of the system hidden from our explorations. Congestion, effusion of serum or of plastic lymph, hemorrhage, fatty de- generation, the effects of pressure on various tissues, together with the divers processes of absorption and repair, can be seen in so distinct a maimer as already to throw much light on general pathology, and to aff()rd good promise of future discovery. Many of these improvements have directly resulted ^ EKCENT ADVANCES IN OPHTHALMIC SCIENCE. from tlie invention of certain instruments, by which we are enabled to explore the interior of the eye with almost as much ease as we can its external surface, and determine its condition with nearly equal cer- tainty. An account of the recent advances in oph- thalmic surgery would therefore be scarcely complete without a description of the means which have facili- tated them. THE OPHTHALMOSCOPE. Notwithstanding some isolated observations of reflection from the back part of the eye, it was till lately generally believed that rays of light reaching the posterior portion of a healthy eye were absorbed by the pigment layer of the choroid, and that none were returned to convey an image of its interior to another eye. This error was due to the fact, that in the ordi- nary inspection of the eye its fundus is but feebly illu- minated, owing to the necessary interposition of the observer's head between it and any available source of light. Fig. 1. Illumination of the retina by a candle-flame. Figure 1 represents an eye having a portion of its fundus illu- minated by rays from the flame of a candle. If now, as is shown in the figure, the eye is accommodated for distinct vision at the' distance of the candle, a minute but clearly defined inverted image of the flame will be formed at the posterior pole, in the region of tlie macula lutea, while the general surface of the ret- 4 RECENT ADVANCES IN OPHTHALMIC SCIENCE. ina is left in comparative darkness. In order to obtain a view of this illuminated region it is necessary that some rays of light from it shall enter the eye of the observer ; but these emergent rays can leave the observed eye onl}' in the inverse direction to that in which the illuminating rays enter it, that is, in the exact direction of the candle. It is evident, however, that if the ob- server's head be interposed between the candle and the observed eye it will cut off the illuminating rays from all that part of the retina which is in the line of vision, while, on the other hand, if he attempt to obtain a view from a point beyond the candle the emergent rays will be intercepted and his eye dazzled by the flame. N. B. In the plates illustrating the principles of the oph- thalmoscope, what is termed a diagrammatic eye has been drawn, representing the total refraction of the cornea, aqueous, crystalline, and vitreous, as if effected by a single refracting medium of uniform density. The demonstration is thus simpli- fied, and the confusion avoided which would result from an attempt to show the separate action of the crystalline lens in figures so limited in size. The ophthalmoscope enables us to obviate this dif- ficulty. This beautiful invention of Helmholz consists in placing before the eye of the observer a mirror, by which rays from a luminous object can be thrown into the observed eye, in the direction they would have if they came from the eye of the observer. Being refracted by the transparent media, they fall upon and illuminate a certain portion of the retina. This illu- minated part of the retina becomes now a source of luminous rays, which emerge from the eye in the THE OPHTHALMOSCOPE. 5 same direction in which the illuminating rays entered it, that is, in the direction of the mirror. In order that these rays may reach the eye of an observer, either the mirror is made wholly or in part of a trans- parent material, or it is pierced with a small aperture at or near its centre. The mirror of Helmholz consisted in superposed plates of thin glass, usually three in number, placed obliquely before the eye. On the rece-ption of the emergent rays from the observed eye, a part of these were again reflected towards the luminous object, their original source ; but another portion passed through the mirror and entered the eye of the ob- server placed behind it. Fig. 2. Original Ophthalmoscope of Helmholz, consisting of a plane mirror made up of several plates of transparent glass. Figure 2 repn placed so as to receive the rays b RECENT ADVANCES IN OPHTHALMIC SCIENCE. of light reflected by the plane mirror D E from a single point ♦ of any luminous body, such as the flame of a candle. The mir- ror being made of a transparent material, such as plate-glass, a portion of the illuminating rays from * will pass through it, in the direction of the dotted lines, and be lost, while another por- tion will be reflected into the observed eye, and wiU light up the point N at its fundus. The emergent rays from N will, in like manner, be in part reflected back to *, but a part will pass directly through the mirror in the direction of A, and thus may be received by the eye of an observer. Silvered or metallic mirrors, having greater illumi- nating power, have been generally substituted for the plates of glass as employed by Helmholz ; in this case the observer looks through a small perforation made for the purpose in the centre of the mirror. Fig. 3. Ophthalmoscope, consisting of plane mirror of metal or silvered glass with central perforation. Figure 3 is the same as Figure 2, with the exception that the mirror D E is made of metal or silvered glass, with a small aperture through its centre. By this arrangement a portion of tlie illuminating pencil falling upon the surface of the mirror is reflected into the observed e}e, and is brought to a focus at N, THE OPHTHALMOSCOPE. 7 while the portion of the emergent pencil which falls upon the hole in the mirror passes through in the direction of A. As the rajs thus received from the fundus of an eye under examination are ordinarily shghtly conver- gent, they may be rendered parallel, and thus better disposed for the formation of a distinct image on the retina of the observer, (whose eye, if normal, is adapted either for parallel or for divergent rays,) by placing a concave lens behind the mirror. Examination in this manner constitutes what is termed the direct method, and gives an erect and greatly enlarged image of the fundus of the eye ex- plored ; different portions of the retina being suc- cessively brought into view by slightly changing the position of the mirror and of the eye of the ob- server. The emergent rays may also be rendered parallel, in many cases, without a concave lens, by simply re- quiring the patient to look at an object at a distance, by which action his eye accommodates itself for par- allel incident rays, and the emergent rays undergoing the same refractive conditions become parallel. At the same time, the rays which enter the eye from the mirror, coming from an object nearer than the distance for which the eye is accommodated, and being there- fore divergent, are not brought to a focus upon the retina, but behind it, and therefore form upon the retina a circle of dispersion, by which a somewhat larger portion of its surface becomes illuminated. 8 RECENT ADV ANTES IN OPHTHALMIC SCIENCE. The use of a concave instead of a plane mirror af- fords a better illumination, as the rays being conver- gent when they enter the eye, are brought to a focus at a short distance behind the lens, and crossing each other there, diverge to form a circle of dispersion of such size as to light up a considerable surface of the retina. Fig. 4. Ophthalmoscope, with concave metallic or silvered glass mirror, showing greater extent of illumination ; also showing the use of a concave eye-glass. Figure 4 illustrates the use of a concave mirror, D E, in- stead of the plane ones shown in Figures 2 and 3. By com- paring this figure with the two former, it will be seen that a very much larger pencil of light from the luminous point * is made to enter the pupil of the observed eye, thus insuring a very bril- liant illumination of its fundus. It will be observed, also, that tlie illuminating rays converge to a focus in front of the retina, from which point they again diverge so as to light up a considerable surface instead of the single point N. The small concave eye-glass L is placed behind the hole in the mirror in order to render the rays from the observed eye parallel or slightly divergent, thus fitting them to form a dis- tinct image on the retina of the observer. The same form of THE OPHTHALMOSCOPE. 9 eye-glass is required with the mirrors shown in the two for- mer figures. If the patient or the observer happens to be strongly hypermetropic the eye-glass may often be dispensed with. The substitution of reflected light for the luminous object itself, and its return, after illumination of the observed eye, through the mirror to the eye of the observer, forms the first principle of construction of all the common forms of the ophthalmoscope. The numerous modifications of the instrument have resulted from efforts to increase the extent and degree of illumination, to enlarge the field of surface visible at one and the same time, and, lastly, to avoid the ne- cessity of frequent changes of lenses to correct refrac- tive anomalies in the eyes both of the patient and of the observer. From the desire to fulfil these indications has arisen the " indirect " method of examination, where an in- verted image of the fundus of the eye is perceived by the observer. In this mode of exploration, a bi-convex or plano- convex glass, of from two to four inches focal distance, is held near the observed eye. By this means two results are obtained; — the rays from the mirror are rendered yet more convergent, and after refraction by the crystalline they form a large circle of dispersion, illuminating a considerable portion of the fundus ; and, secondly, the rays emerging from the illuminated ret- ina are brought to a focus in repassing through the 1* 10 RECENT ADVANCES IN OPHTHALMIC SCIENCE. convex lens, forming a brilliant and clearly defined inverted imao-e. Fig. 5. Ophthalmoscope, combining the concave miiTor and a convex objective lens, showing the greatly increased field of Illumination. The illuminating rays only are represented. Figure 5 shows the combined effect of the concave mirror 1) E and the objective lens L in rendering the ilhmiinating rays strongly convergent, and consequently lighting up a very large portion of the Hindus of the observed eye. By the employment of this lens all nice distinctions as to the myopia, hypermetropia, or accommodation of the observed eye, Avhich must -without its use be taken into account in searchino- for the retinal imao-e, may be comparatively disregarded ; and we know that this image must now be found within a sliort distance of the principal focus of the objective lens. Figure 6 shows the action of the objective lens L in form- ing at a', a, a" an inverted image of the portion of illuminated retina N', N, N". The dotted lines to the right of a', a, a" which pass through the hole in the mirror are continuations of the rays which by their convergence have formed the image THE OPHTHALMOSCOPE. 11 Fig. 6. Ophthalmoscope with concave mirror and convex objective lens, showing the formation of an inverted image. The illuminating rays are omitted. a', a, a''. The whole image a', a, a", corresponding to the whole surface N', N, N", is therefore visible at a single glance to the eye of an observer placed directly behind the mirror, whereas without the objective lens only a very small portion of the reti- nal surface can be seen at a time, and the examination of any extensive region can only be made, as it were, piecemeal, by moving the mirror and thus bringing different parts successively into view. It is only requisite to bring the eye of the observer a little nearer to the observed eye if the latter is my- opic, and the contrary in a case of hypermetropia. Fig. 7. Diagram illustrating the position of the inverted image at or near the prin- cipal focus of the objective lens. Figure 7 is intended to illustrate the various positions of 12 RECENT AD V ANTES IN OPHTHALjnC SCIENCE. the inverted image formed by the objective lens L, under differ- ent refractive conditions of the observed eye. The three condi- tions of myopia or forced accommodation, emmetropia, and hy- permetropia are represented in the three directions of the emer- gent rays ; viz. myopia by the rays which converge to A', em- metropia by the parallel rays A, A, and h}'permetropia by the divergent rays A", A". In the case of the emmetropic eye ac- commotlated for an infinite distance, the rays A, A, which emerge parallel from the observed eye, are brought to a focus and form an inverted image of the retina at the principal focus, F, of the objective lens L. If the observed eye is myopic or accommodated for near objects, say at the distance A', the emer- gent rays, which are already somewhat convergent, will be brought to a focus at a point a little nearer to the lens L than its principal focus, say at F'. If, on the other hand, the ob- served eye is hypermetropic, the emergent rays, although some- what divergent, are by no means sufficiently so to neutralize the convergent action of the powerful lens L ; they are therefore brought to a focus, not at or within the principal focus of the lens L, but beyond it, say at F'. In the case of an excessively hypermetropic eye, or after the removal of the crystalline, it may be sometimes advantageous to employ an objective lens of greater power than usual, say one of less than two inches focal length ; but for the vast majority of eyes, a lens of from two to four inches focal length is sufficient. This image may be magnified, or tlie eye of the observer, if presbyopic or hypermetropic, aided by placing a second convex glass of less power, say of ten inches focal distance, behind the mirror , M^hich must, perhaps, in this case be placed nearer the aerial image, so as to bring this latter within the range of the second glass. THE OPHTHALMOSCOPE. 13 Fig. 8. Use of convex eye-glass in the examination of the inverted retinal image. Figure 8 shows the use of a convex eye-glass in viewing the retina by means of its inverted image. If the objective lens L is chosen of moderate power, and especially if the observed eye is strongly hypermetropic, the image a will be formed so far from the lens L as to necessitate the removal of the observer, and consequently of the mirror, to an inconvenient distance. This difficulty is entirely obviated by the employment of a con- vex eye-glass placed behind the hole in the mirror D E, which gives the additional advantage of a more highly magnified image. The image may be magnified to almost any desired degree by the employment of a weak object-glass and strong eye-glass. For this method of examining the eye by the in- verted image, concave silvered or metalHc mirrors are employed, in order to secure a sufficiently exten- sive and brilliant illumination ; but for certain exami- nations in the erect image, or where the pupil has not been dilated by atropia, or, especially, where great sensitiveness of the retina is present, the plane mirror of Helmholz, composed of thin plates of glass, is often to be preferred, owing to the less intensity of the light reflected by it. 14 RECENT ADVANCES IN OPHTHALMIC SCIENCE. The direct metliod, with the upright image, is par- ticularly well adapted for the exploration of the parts of the eye lying anterior to the retina. Opacities or other changes in the vitreous or the crystalline lens can thus be detected, and their rela- tive positions determined, with great readiness and certainty. MODE OF USING THE OPHTHALMOSCOPE. • In a very large proportion of ophthalmoscopic ex- aminations, especially where it is only desired to ob- serve the optic disc and its surrounding parts, — as, for instance, in cases of myopia, where we wish to deter- mine the presence or absence of posterior staphyloma, — it is unnecessary to dilate the pupil ; but as the eye can be more readily as well as more thoroughly ex- plored after the pupil has been enlarged by the use of atropia, it is sometimes desirable or important to employ it. A weak solution, say of one grain to the ounce of water, will generally be sufficiently effective for this object, and its influence soon passes off, with- out subjecting the patient to the annoyance caused by the long-continued mydriasis and the loss of accom- modation which is occasioned by the use of a strong solution. The patient should be seated in a darkened room, rear a table. On this an argand or petroleum lamp or gas-light is placed, a little behind the plane of his THE OPHTHALMOSCOPE. 15 forehead, and nearly on a level with it. The eye will thus receive only the rays reflected from the mirror. The surgeon seats himself opposite, with his eye at about the level of that of tlie patient, or a little above it. If examining by the "direct" method, the light from the mirror is now to be directed to the field of the pupil, and the surgeon, looking through the aper- ture in the mirror, })erceives the bright reflection from the fundus of the eye. If the vessels of the retina are not distinctly seen, the instrument and the eye of the observer are brought a little nearer to or removed a little farther from the eye looked at, until the point of clear perception is ascertained. If this does not succeed, the observed eye may be at fault ; if myopic, or persistently accommodated for near objects, a con- cave lens must be placed behind the mirror, and imme- diately in front of the eye of the observer ; if hyperme- tropic in any marked degree, it may be necessary to use a convex glass in the same position. In examin- ing a normal eye, a concave glass of moderate power (say twelve inches) is often very useful in correcting unconscious efforts at accommodation on the part of the patient, and perhaps also of the surgeon. In ex- amining simply presbyopic eyes this may usually be dispensed with. To bring into view the optic disc, or entrance of the optic nerve, the patient is directed, if the right eye is to be examined, to look at some object over the 16 RECENT ADVAN'CES IN OrHTHALMIC SCIENCE. right shoulder of the observer ; if the left eye, he may be told to look toward the observer's left ear ; each eye, in short, being turned slightly iuAvards and up- wards whilst being looked at. The optic disc affords a good starting-point, from which the exploration may be extended in all directions, the patient being re- quired to turn his eyes slowly to the right, left, up- wards, or downwards, so as to bring successively into view various portions of the retina. The macula lutea is brought into view when the patient looks directly at the mirror. If the pupil has previously been en- larged by atropia, nearly the Avhole of the retinal surface can thus be inspected. If the "indirect" method be employed, the convex lens is held near the observed eye with the thumb and finger of one hand, whilst the other holds the ophthalmoscope. The lens should be held somewhat .obliquely, so that the reflection of the mirror from its two surfaces may not interfere with the observer ; and a plano-convex lens has an advantage over the bi- convex, as mvino; less of this disturbinn; element. As observed eyes differ in their refractive power, the lens must be held slightly nearer to or farther from the eve, in order to gain at the focus of the lens a dis- tinct image of the retina. A moment's trial suffices to establish the proper position. The observer at the same time keeps the ophthal- moscope and his eye at such distance from the focal point of the lens (at or near which the image is to be THE OPHTHALMOSCOPE. 17 formed) as is adapted for his clear perception of small objects. The aerial image being thus brought to a determi- nate point, a short distance from the observed eye, and rendered clear, it may be enlarged, if desired, by placing behind the ophthalmoscope a convex lens of say ten inches focus. The instrument is to be held at about the focal distance of this secondary lens from the inverted image formed at or near the principal focus of tiie objective lens, as already described. In examining the refractive media of the eye, accu- rate ideas respecting the situation and form of opaci- ties or effusions in those, media may be best obtained by the aid of the mirror alone. If these are in the anterior chamber or the crystal- line lens, their nearness to the surface allows of their being detected ; and if in the vitreous, the cornea and crystalline together act as an auxiliary magnifying lens to render them more obvious. In viewing ob- jects situated in front of the retina, we may see them, if very brilliant, by reflected light ; but in the majority of cases, being themselves of a dull color, they a])i)ear, by reason of their opacity, as dark spots or lines, ob- scuring in part the more brilliant fundus of the eye. Figure 9 illustratos the use of the ophthahnoscope in the in- vestigation of opacities or floating bodies in fi-ont of the retina. Let A B represent a floating body in the vitreous; being in front of the posterior focus of the eye, the rays from it emerge divergent from the eye, although less so than before traversing B 18 RECENT ADVANCES IN OPHTHALMIC SCIENCE. Fig. 9. Use of the ophthalmoscope in the investigation of opacities or floating specks in the lens or vitreous. the crystalline and cornea. The rays from the point A, there- fore, after emerging from the eye, assume the direction A" A", as if they had really come from the more distant point A', and the rays from B assume the direction B" B", as if coming from the point B'. Tlie effect is, that the eye of an observer placed in front of the observed eye will see at A' B' an enlarged erect image of A B. It would be useless to attempt, here, an account of the numberless patterns of ophthalmoscopes which have been invented and found more or less of favor. The most convenient for ordinary purposes are small concave mirrors having a focus at about the ordinary distance at which small print can be read. That of Liebreich may be mentioned as a good example. This is fastened to a short handle, and has at one of its edges a hinged support in which a small convex or concave glass may be fixed, which can at will be turned away from or placed behind the mirror. In the case containing it is also a convex lens or two, to THE OPHTHALMOSCOPE. 19 be used in examinations with the inverted image, and several small glasses of different foci. FIXED OPHTHALMOSCOPES. Besides the more portable ophthalmoscopes, large instruments have been constructed on the same prin- ciples, which afford a ready means for exhibiting the phenomena to be observed within the eye to those who have not acquired facility in these explorations. They are provided with supports for the patient's head, and a point upon which, after it has been suit- ably adjusted, he can fix his attention, thus keeping the eye in any wished-for position, and allowing the portion of its fundus which it is desired to exhibit to be seen by a large number of observers in succession. BINOCULAR OPHTHALMOSCOPES. In order to obtain the advantage of vision with both eyes, a most ingenioias instrument has been de- vised, which, by a combination of rhombohedral and prismatic glasses bcliind the mirror, allows an image to be formed on corresponding parts of the retina in each of the observer's eyes. The advantages of this instrument are, that, as in the stereoscope, objects may be seen in apparent relief, and any inequalities in the retinal surface, whether excavation of the optic disc, posterior staphyloma, or encx'oaching growth of en- 20 RECENT ADVANCES IN OPHTHALMIC SCIENCE. cephaloid or other tumors towards the centre of the globe, may be more readily discerned, and their de- gree estimated. The instrument forms one of the most beautiful and ingenious applications of the principles of optics to the furtherance of scientific research ; but it has the dis- advantage of being somewhat less quickly adapted to the eye under observation than the small ophthalmo- scope of Liebreich. Figure 10 represents the optical principle of the Binocular or Stereoscopic ophthalmoscope. N is the fundus of the observed eye, and N' and N" of the left and right eye of the observer. The objective lens L forms at F an inverted image of the illu- minated retina N. Instead, however, of viewing the image F directly through the hole in the mirror D E, the two rhombo- hedra H G K I and H G' K' I' are interposed in such a position as to receive the rays as soon as they have passed through the hole, and to transmit them, by total reflection, half to the right hand toward G' K', and the other half to the left in the direction of G K. Here they undergo a second total re- flection, and are then refracted slightly outward by the small prisms P and P', to be received by the two eyes of the observ- er and brought to a focus upon his two retinse, N' and N". It will be seen now, by inspecting the figure, that the rays from tlie left side of the point N, shown dotted in the diagi'am, after helping to form the image F, cross to the right side so as to fall upon the right-hand rhombohedron H G' K' I', and finally come to a focus and form an image upon the retina N" of the right eye of the observer. The rays from the right side of N, on the other hand, are in like manner received by the left-hand rhombohedron II G K I, to be conveyed to the observer's left eve at N'. The result is, that if there is anv irregularitv of THE OPHTHALMOSCOPE. Fig. 10. The Binocular Ophthalmoscope. 21 22 RECENT ADVANCES IN OPHTHALMIC SCIENCE. surface at N, as, for instance, an excavated optic disc, the right and left hand bundles of rays form somewhat different images in the two eyes of the observer, and from the combination of the two impressions stereoscopic vision results. The Binocular Ophthal- moscope is also of use, by enabling the observer to use both eyes at once, even where there is no irregularity sufficiently marked to produce the impression of solidity or excavation, — binocular having always an advantage over monocidar vision. AUTO-OPHTHALMOSCOPES. An instrument has also been devised by means of which an observer can with one eye examine the retina of his other eye ; and, yet further, an instrii- ment by which the retina of an eye can inspect it- self, — an image of its papilla being thrown upon its macula lutea. normal appearances to be observed with the ophthal:\ioscope. In a healthy eye, the optic disc, or papilla, as it is often termed, — the spot of entrance of the optic nerve, — is considerably lighter in color than the sur- face of the retina, and forms a whitish disc, some- times having an almost silvery reflection. From this the arteries emerge, generally in two superior and inferior branches, which subdivide as they run toward the peri[)hery of the retina ; and to it return the veins, distinguishable from the arteries by their darker THE OPHTHALMOSCOPE. 23 color and less direct course. In a certain number of eyes in which the fundus is really normal the optic disc appears to have an oval contour instead of its usual circular form. This illusion is often due to a disturbed refraction in the cornea, in consequence of variations of curvature in its different meridians. This oval appearance of the papilla depending on astigmatism of the cornea, and not on any actual de- formity of the papilla itself, is not to be confounded with a pathological change in its outline often seen in extreme myopia, which will be hereafter described under the head of posterior staphyloma. But an ap- parently oval image will also be seen if the objective lens is held very obliquely. Differences of color are often observed in the optic disc ; slightly bluish spots and appearances of excava- tion being seen, especially at its central portion, in eyes which are functionally perfect. These are due to differences in the aspect of the lamina cribrosa and the nerve fibres passing through it. Another varia- tion from the normal type is found in the existence of a more or less complete dark crescentic line of pig- ment at the margin of the disc. But this is not to be deemed abnormal, it being compatible with excellent vision. The general surface of the retina appears pinkish or reddish, according to the amount of pigment in the choroid beneath. The retina itself can, in most cases, scarcely be distinguished, but may be some- 24 RECENT ADVANCES IN OPHTHAOnC SCIENCE. times made out as a thin grayish layer overspreading the choroid. In albinos, Or persons of very light com- plexion, the quantity of pigment matter in the cho- roid is so small that the choroidal circulation may be distinctly seen, the vessels being paler and more tortu- ous than those of the retina, and evidently underlying the latter. In those of dark complexion these vessels of the choroid are masked by the abundant pigment. Where the amount of pigment is very small, the por- tion of the eyeball bounded posteriorly by the choroid and anteriorly by the iris fulfils only imperfectly its office of a dark chamber ; and too great amount of light passing through the sclerotica and iris into this chamber causes confusion of the retinal images and photophobia. The macula lutea, the central spot of visual percep- tion, is situated about the distance of three lines from the papilla, towards its outer side, and is brought into view when the eye looks directly forward. It often cannot be readily distinguished on ophthalmoscopic examination, since no vessels converge towards it, as they do towards the papilla; but not unfrequently there is an evidently increased amount of pigment granules around it, marking its situation and leading to its discovery on close inspection. This part of the eye should always be carefully examined where there is reason to suspect retinal disease, as it is a frequent seat of pathological alterations, which are easily per- ceived if looked for. THE OPHTHALMOSCOPE. 2o In some instances, not abnormal, the entire surface of the fundus, except the papilla, seems of an almost brownish color, divided into patches by choroidal ves- sels anastomosing in all directions. Overlying this network are seen the retinal vessels in their usual course. Xhis brief sketch of the appearances revealed by the ophthalmoscope in healthy eyes, seemed to have its place as an accompaniment to an explanation of the instrument itself. But, to avoid repetition, descrip- tions of pathological conditions will be reserved, to be connected with some account of the diseases whicii give rise to them. ADVANTAGES OF THE OPHTHALMOSCOPE. It is not claiming too much, to assert that the oph- thalmoscope has done more to increase our knowledge of diseases of the eye than had been accomplished during a century by all other means. The practi- tioner is not now oblijred to include a large number of deep-seated diseases of the eye under the designa- tion " Amaurosis," to which the well-known remai'k of Walther was unfortunately but too apropos, — "A condition where the patient sees nothing, and the doctor also — nothino;." '•'' Jener Zustand, hei ivel- chem der Kranke 7iichts sieht, aher der Arzt audi nichU^'' He is relieved from many embarrassing un- certainties in diagnosis, painful to himself, and more 2 26 RECENT ADVANCES IN OPHTHALMIC SCIENCE. or less detrimental to his patient, — and is no longer in the dark ; but, in regard to the interior of the eye, can speak of what he knows and testify of what he sees. As accurate diagnosis is and must be the basis of all successful treatment, the oculist can already point to brilliant therapeutic triumphs over diseases hitherto deemed incurable, which have directly resulted from the knowledge acquired by means of this instrument. LATERAL ILLUMINATION. Another mode of exploring the anterior and cen- tral portions of the globe, which offers many advan- tages and great facility, is that by lateral or oblique illumination. The patient is placed with the light near his temple, and this is concentrated, by means of a lens, upon the cornea, iris, crystalline, or vitreous, wherever morbid changes may be perceived or suspected. The obser- ver's eye may be placed directly in front of the eye examined, or, still better, at the point where he Avill receive the reflected rays at the same angle as that of their incidence. He may magnify and give greater clearness to the appearances inspected by employing a second lens if necessary. In this manner we may readily detect even the slightest opacities or irregularities in the cornea, the faintest traces of commencing cataract, foreign bod- ies in the anterior chamber or lodged in the iris, as THE OPTOMETER. 27 well as many alterations in the vitreous, hemorrhagic, or other effusions there, and, sometimes, bulging folds of a separated retina. The ease and rapidity with which this means may be employed is not a slight recommendation. OPTOMETERS. We owe to Professor Von Graefe the introduction of an instrument for determining the refractive power of the eye, and ascertaining the focal strength of glasses required by a patient, without the tedious trial of numerous lenses of different power. Its principle is that of the Galilean telescope. In theory, this instrument appears accurately suited to its proposed object. Practically, however, it is found that its indications oflen need to be corrected by other tests, A convenient optometer may be made by a slight modification of the ordinary measure used by shoe- makei's. The stationary upright piece is fitted to hold a lens, and the movable piece a card on which are fine printed letters. Placing this card at the Avished- for distance in inches, the power of glasses required may be ascertained by changes of the lens till the proper number is found, or by holding such a second supplementary lens before the first as will render the print distinct, and adding or subtracting its power. A plate representing this instrument is given in the 28 RECENT ADVANCES IN OPHTHALMIC SCIENCE. chapter on the range of accommodation, — it heing also adapted for determining this. (See Fig. 24.) TEST LETTERS. It has been very desirable to have some generally accepted standard by which the amount of visual power or acuteness of sight, and the range of vision, might be ascertained, and which, being referred to in published accounts of cases, should be universally un- derstood. Professor Edward Jaeger has published a scale, beginning with the smallest type used in print- ing, and extending to letters of such size as may be easily read by a normal eye at a distance of twenty feet. More recently Dr. Snellen of Utrecht has published a series of test-types in which the letters are made up of cubes. They are arranged without order, F H K O S, &c., so that actual vision is required to read them, and they cannot be guessed at when only part of a line is seen, as may often be done with ordinary words. A similar series of test-letters has been prepared by Dr. Dyer of Philadelphia. I have appended to this work a series of letters sim- ilar in plan to that of Dr. Snellen. The selection has been carefully made, so as to include only those letters which have throughout nearly a miiform size, without masses of black in some parts, and they are all of the TEST LETTERS. 29 same style. Those of rounded and square outlines have been placed alternately, to give equality to the interspaces, as far as might be. The larger sizes hav- ing been most carefully engraved and printed, copies of the letters, as adapted for each of the distances given, were obtained by accurate photographic reduc- tion with mathematical exactness, and were then cut on wood, impressions from which give a very distinct outline. Two other series have been added as reading tests, — one of Gothic letters, the other of handsomely cut Roman type. Both of these are almost perfectly ac- curate in their gradations of size, — and correspond, the first with the same numbers of Snellen's scale, the second with those of Jaeger's test. Parallel horizontal and vertical lines, for the deter- mination of the presence and direction of astigmatism, are included v;ith the other tests. Tiie figures placed above each series of letters indi- cate the distance, in feet, at which this No. should be read by a normal eye. No. XX, for example, should be read at twenty feet ; but if this No. can be read only at ten feet distance we say V, which expresses the acuteness of vision, is equal to |^ ^ ^. If No. VI, which should be read at six, can be read only at two feet, V = | = 1. Should the patient be unable to distinguish the letters at normal distances, we may then proceed to ascertain whether the inability depends on abnormal 30 RECENT ADVANCES IN OPHTHALMIC SCIENCE. focal power, on opacity of the transparent media, or on loss of susceptibility in the nervous structures in which lies the faculty of perception. If the deficiency arise from the first cause alone, it is corrected by the aid of irlasses : if from either of the other two condi- tions, we must look to proper remedial measures for its cure. LIMITATION OF THE VISUAL FIELD. We are all aware that we are not only able to dis- tinguish objects clearly at a given point, but that we have also perception, more or less distinct, of things lying within a circle extending to a considerable dis- tance around that point. This is termed the field of vision, and it is not unfrequently important to learn whether it still retains its normal limits. This may be done by placing the patient at the dis- tance of a foot from a blackboard or a frame in which has been placed a sheet of blue tissue or other paper. On the centre of this a small cross is marked with chalk or pencil, and the patient is directed to fix his eye upon this point, the other eye being closed. The crayon is now moved over the paper, being carried successively upwards, downwards, and to the right and left horizontally, marking in each direction the extreme limits at which the patient perceives it. The same plan is followed for all the intermediate points, and the outline thus drawn upon the board or paper LIMITATION OF THE FIELD OF VISION. 31 shows the hmit of the field of visual perception. The other eye may then be tested in the same way. Visual power may be nearly perfect at a 'central point, as sometimes in glaucoma, while it has become extinct to within a small space around this point ; or it may be preserved over a considerable portion of the field upwards or downwards, while wanting in other parts, as in cases of separation or apoplexy of the ret- ina. These drawings will illustrate the manner in which the extent and seat of morbid changes may be defined. Fig. 11. The figure to the right exhibits the effect of separation of the retina. The space occupied by the fluid having utterly lost its perceptive power is represented in the circular field of vision by a black space, next to this is a limited shaded margin where slight perception, perhaps sufficient to distinguish a candle flame, remains, and in the rest of the field vision may be tolerably good, so long as the separation is confined within moderate lim- its. Similar appearances sometimes follow the effusion of blood, in cases of apoplexy of the retina. The figure to the left shows a small space in the centre of the field where vision remains distinct, a shaded halo marks the 32 RECENT ADVANCES IN OPHTHALMIC SCIENCE. limit of imperfect perception, and beyond this all is dark. Such are the conditions found in some cases of glaucoma and in the form of choroiditis sometimes termed retinitis pigmentosa. The sensibility of the retina may be determined in cases of cataract, and sometimes in other diseases, by employing candles instead of the point of a crayon. One candle, at which he is to look, is to be placed be- fore the patient's eye at the distance of a foot, while another is moved before his eye, at the same distance from it, and the limits noted beyond which he no longer perceives the flame. This is of importance where there is reason to suspect that other and more serious disease may exist behind the lenticular opacity. The question whether or not there be limitation may be rapidly tested, by directing the patient to look steadily at the surgeon's nose while it is ascertained whether he sees the hand moved in different positions before his eye within the usual lateral range of vision. Should any limitation be thus detected, its precise amount and seat may be determined as above de- scribed if it be thought important. INSTRUMENTS DEMONSTRATING THE AC- COMMODATIVE FUNCTIONS. Very ingenious pieces of apparatus have been de- vised for demonstrating that the power possessed by the eye of accommodating itself to objects at various NEW THERAPEUTIC AGENTS. 33 distances, is exercised by means of an increase of con- vexity in the surfaces of the crystalline lens ; and others for measuring the range and latitude of accom- modation. These Avill be again referred to. It may now suf- fice to say, that the demonstration afforded by them is " ocular," in more senses than one, and leaves nothing to be desired. NEW THERAPEUTIC AGENTS. OxE substance of exceptional properties and uses, Calabar Bean, Physostigma Venenosum^ deserves spe- cial mention. In his work on Diseases of the Eye, published no longer ago than 1861, M. Stellwag von Carion, of Vienna, one of the most distinguished of the German oculists, says, " We possess no means of effecting contraction of the pupil." Even then, experiments were in progress which were to endow us with this invaluable acquisition. It is to Drs. Frazer and Robertson of Edinburgh that we are indebted for the introduction of the Cala- bar Bean into our materia medica ; Dr. Frazer having first announced, in his inaugural thesis, its power- of contracting the pupil, and Dr. Robertson having ex- perimented upon its practical uses and brought it prominently to the notice of the profession. Hitherto it had been regarded as an object of curi- osity merely, having been sent to Europe by mission- 2* c 34 RECENT ADVANCES IN OPHTHALMIC SCIENCE. aries residing on the Calabar coast, as an article era- ployed by the natives for purposes of ordeal, as a test of the guilt or innocence of accused persons. Eaten in any considerable quantity it has active poisonous properties, and if not ejected by vomiting, causes speedy death. More than sixty children, one at least of whom died, were recently poisoned at Liverpool, from having picked up and eaten some of the beans which had been thrown out with rubbish from the hold of a vessel. The bean is about an inch in length, and covered with a hard, brownish husk or envelope. Its alkaloid or active principle not having been yet extracted in any quantity, if at all, the alcoholic ex- tract, rubbed up and diluted with glycerine or syrup, — or paper which has been dipped into a solution of the extract, — are the forms in which the remedy is obtainable for medical use. A very minute quantity of the diluted extract ap- plied to the conjunctiva, causes extreme contraction of the pupil in about fifteen minutes ; and this appar- ently continues as long as the dilatation produced by an equal amount of extract of belladonna, though, as of course we might expect, its influence is counter- acted by a small quantity of atropia, which is a so much more concentrated preparation. Besides its action upon the pupil, it affects the ac- commodative power and renders a person temporarily myopic, — in all these respects apparently acting as the antagonist of belladonna. On account of the ANESTHETICS. 35 small number of rays which can pass through the diminished pupil, the perception of objects is rendered somewhat indistinct, as if seen at twilight. Its application to the eye is sometimes followed by slight dull pain in the globe or the supra-orbital re- gion, but this is usually of brief duration. This welcome remedy is to be of great service in the treatment of mydriasis, — in hernia of the iris occurring near the margin of the cornea, — and in the manao;ement of some of the disturbances of the fac- ulty of accommodation. The limited experience al- lowed by its recent introduction has already proved its great value in cases which seemed amenable to no other treatment. ANESTHETICS. It has been the good fortune of the younger men of the present generation of physicians to receive the boon conferred on surgery by the introduction of anaesthetics. In their application to operations on the eye these agents have been of incalculable benefit. Many of these operations, as, for instance, excision of staphy- loma, or removal of a part or the whole of the globe itself, are exceedingly painful ; many, which involve less actual suffering, appear formidable to the patient, because he thinks the eye so sensitive. In many other operations, delicate rather than pain- 36 RECENT ADVANCES IN OPHTHALMIC SCIENCE. fill, — such as those for iridectomy, separation of adhe- sions of the margin of the pupil, and some of those for cataract, — it is a great advantage to have the motor muscles of the globe, Avhich are but slightly under the control of the will, rendered passive by ansesthetics ; that we may have nothing to fear from spasmodic pressure of the muscles upon the eyeball, or sudden involuntary movements. If the subject be a child, even the slightest operation could formerly be done only under forcible restraint, not only controlling the movements of the body, but of the eye itself. Now, in operations for congenital cataract, strabis- mus, &c., half the objections to surgical interference are removed by the fact of the unconsciousness of the patient. The ability to insure complete repose of the eye gives yet further advantages : it allows of seizing of the conjunctiva with forceps and turning the globe in any direction, to give convenient access with instruments to certain parts, and it permits of so much deliberation that the intended manoeuvres may be more nicely executed. anj:sthetics in operations for cataract. The use of chloroform or ether, till complete insen- sibility is induced, greatly increases the chances of success in the operations for extraction of hard cata- ract and in the removal of soft cataract by suction. In extraction of cataract by the ordinary flap oper- ANESTHETICS. 37 ation, ansestliesia allows of fixation of the globe in any desired position, — so that the upward section of the cornea, which offers most advantages, may be made with nearly as much ease as the lower. It ren- ders prolapsus of the iris or loss of vitreous during the operation less probable, by preventing all compression from spasmodic contraction of the recti muscles, and it allows of the careful removal of any fragments of cortical substance which may remain after the exit of the mass of the lens. Should a suture be employed, as will be hereafter proposed, its introduction will be facilitated by the passiveness of the eye. Almost the sole objection to the use of ether in ex- traction is found in the possibility of loss of the vitre- ous or of intra ocular hemorrhao;e durino; efforts of emesis induced by the anassthetic. This accident may be avoided, in great part, if care be taken to have the stomach nearly empty at the time of administration, and its dangers may be obviated by hastening the ap- plication of the compressive bandages, which retain the edges of the corneal wound in proper apposition. The use of chloroform does not involve this objection in the same degree ; but it is less safe than ether, though unquestionably very slight risk attends its careful employment. Should the extraction be com- bined with iridectomy, as proposed by Jacobson and Moreen, or effected by means of out-scooping with a spoon through a small corneal wound and after iri- dectomy, as practised by Waldau, the induction of 38 EECENT ADVANCES IN OPHTHALMIC SCIENCE. anaesthesia becomes yet more important. It allows of the upper section being made, which, though some- what more difficult than the lower, is the only one properly admissible, especially in these methods, — ob- viates all danger of too great separation of the iris by any sudden rotation of the globe, — and, if out-scoop- ing be resorted to, renders the iris less liable to be contused by the spoon. The operation by suction is also much facihtated by previously rendering the patient unconscious and his eye passive by etherization, the danger of contusing the iris or penetrating the vitreous being thus avoided. TENSION OF THE EYEBALL. The fact that in some internal diseases of the eye its tension is augmented by the increase of its con- tained fluids is one of the most important of the re- cent observations in ophthalmic science. It had long been known that in advanced stages of glaucoma the eye felt hard to the touch ; but it is only lately that we have learned to recognize increase of tension as an early symptom, and to mark this condition as an im- portant indication for prompt treatment. The degree of tension may be estimated by placing the forefinger or the first and second fingers upon the closed upper lid, and making gentle pressure upon the globe. One eye may thus be compared with the TENSION OF THE EYEBALL. 39 other, and the surgeon makes a mental estimate of comparison with the normal standard as felt in a healthy eye. Or the first finger of each hand may be placed upon the lid at different points, and press- ure made from one finger towards the other. Prac- tice will soon teach the surgeon to recognize at once, by either of these methods, any abnormal increase or diminution of tension. Mr. Bowman has advised the adoption of a scale of three degrees of plus (-f-) tension, where the eye is harder than in a healthy condition, and three de- grees of minus ( — ) tension, where it is softer than the normal standard. PARACENTESIS OF THE CORNEA. Puncture of the cornea for the evacuation of the aqueous humor is by no means a new procedure, but it has within a few years been much extended in its applications, having been vaunted as a cure not only for ulcerations of the cornea, iritis, and all deep-seated inflammations of the eye, but also for cataract. It is claimed that absorption of the latter may be effected by persevering repetitions of this slight operation ; but as success is said to be attained only after daily evac- uation of the aqueous for a period of weeks or months, it would require incontestable evidence of good conse- quences to lead one to attempt its dispersion by such a method. There seems to be no doubt that an ap- 40 RECENT ADVANCES IN OPHTHALMIC SCIENCE. parent temporary gain may take place, whether, as is asserted, from rehef of choroidal congestion, or from some other cause, it is difficult to determine ; but the plan requires more testimony in its favor before it can be accepted as a reliable curative means. There can be no doubt, however, of its advantages in relicAing some forms of internal inflammation, and it deserves to be more frequently resorted to, especially in iritis. The puncture may be made Avith a cataract needle, or, still better, with a guarded needle devised for this purpose by Desmarres. After evacuation, the ante- rior chamber refills in a few moments, and it is well to empty it a second time by pressing upon one edge of the wound with an Anel's probe. If it be desired to repeat the operation the next day, the wound may usually be reopened with the probe, without resorting to a sharp instrument ; though there is no objection to a second puncture if the first be not readily found. IRIDECTOMY. Among the operations long practised by ophthalmic surgeons which have been considerably modified in the manner of their performance or in their practical applications, is that for iridectomy ; and, as it will fre- quently be referred to, a brief account of the method of doing it in uncomplicated cases is here intro- duced. Every one must have noticed the extreme tolerance IRIDECTOMY. 41 of the iris, although a very sensitive structure, of la- cerations of its tissue in the formation of an artificial pupil. But to Von Graefe of Berlin belongs the credit of extending and generalizing the uses of this surgical remedy for the relief of other affections than those merely depending on closure of the pupil, to which its application was formerly restricted. He has also indicated a certain method of performing it, as being important, in his judgment, to its full success. His opinions as to these points have been to a great extent adopted by most of the distinguished oculists of other countries. If the surgeon undertakes this operation without an assistant, he should be provided with a spring eleva- tor, by which the lids are held apart, leaving both his hands free, and also with a bent triangular knife, a very delicate curved, toothed forceps, and fine scissors slightly rounded at their points. Should he have an assistant who can be relied on, the latter may assume the charge of one of the eyelids, and, if desired by the surgeon, may also control the eyeball and turn it in any direction by seizing a fold of the conjunctiva with another forceps. Etherization is not imperatively necessary, unless the patient is young or very timid, as the pain of the operation is not of any great sever- ity ; but the pain is of such a character, from the tearing of the ciliary nerves, that there is danger of a sudden movement of the globe, causing a too large separation of the iris, if the eye be not firmly held. 42 RECENT ADVANCES IN OPHTHALMIC SCIENCE. The induction of anassthesia is therefore oftentimes advisable, as it allows of the operation being done Avith greater deliberation and delicacy, and of the por- tion of iris removed being accurately calculated. When this operation is done for the relief of glau- coma, or in cases where no special reason exists for the selection of some other part of the iris, it should be performed upwards, in order that the space thus added to the natural pupil may be covered by the upper lid in the ordinary positions of the eye. This is important for cosmetic reasons, as well as to avoid the dazzling caused by an excessive influx of light into the eye, and has been too little regarded. An incision, three or four lines in length, is made with the bent lance-shaped knife, through the scle- rotica, just beyond the margin of the cornea and close to the insertion of the iris, thus entering the anterior chamber at its extreme border. The knife makes its incision by being simply pushed onward, and should the iris and crystalline have been crowded forward by pressure of the vitreous, care will be necessary to keep the point of the knife well towards the inner surface of the cornea, to avoid wounding the ca])sule of the lens and causing traumatic cataract. As the knife is withdrawn, the iris, if free from adhesions, frequently follows it as the aqueous humor flows out, and forms a slight hernia through the wound. If this occur, the iris may be immediately seized by the for- ceps, but should it not prolapse the forceps must be IRIDECTOMY. 43 carefully introduced through the wound and the iris taken hold of near the margin of the pupil. Being drawn out a little Avay, a cut is made with the scissors in the direction of the radiating fibres of the iris, at a point coi'responding with one of the extremities of the incision of the cornea ; the iris is then torn away from its ciliary attachments by slight traction with the forceps, and the flap snipped off with scissors at tlie other extremity of the incision, thus leaving, of course, a loss of substance in the iris corresponding in size with the length of the corneal wound, or less than this if the surgeon prefers to remove a smaller por- tion. Should much blood be effused from the torn vessels into the anterior chamber, it may be evacuated by gentle pressure with the forceps against the posterior edge of the wound ; or, if slight in quantity, or not readily discharged, it may safely be left in the eye, to be dissolved and absorbed as the anterior chamber becomes refilled. Professor Von Graefe insists on the importance of removing a segment of the iris to its very border, — separating it from its ciliary attachments ; as he re- gards the mere removal of a portion of the iris tissue, unless carried to its extreme margin, insufficient to insure a good result in cases of glaucoma and irido- choroiditis. This is certainly not always requisite to complete success ; yet it may be well to carry the loss of substance as far as the ciliary attachments, since 44 RECENT ADVANCES IN OPHTHALJIIC SCIENCE. there is reason to believe that neurosis of. the ciliary branches may be the initial point of glaucomatous disease. Iridectomy may be regarded as involving almost no risk of injury to the eye, if done with proper care and delicacy, — the iris tolerating in a remarkable degree any violence of this kind, and it is unnecessary to sub- ject a patient to long confinement and severe after- treatment. IRIDDESIS. There are certain cases where, either on account of central opacity of the cornea, conicity of its form, or extensive adhesions of the iris to the capsule of the lens, it is desirable to displace the pupil, so as to ren- der it available for vision, while at the same time the conditions which render the natural opening superior to an artificial pupil are preserved as perfectly as pos- sible. This object is attained by an operation termed iriddesis, devised by Mr. Critchett of London. This operation consists in making and maintaining traction of a portion of the iris fibres in such a direc- tion as to give to the natural pupil the Avished-for position, instead of forming a new pupil or enlarging the previously existing one by a loss of substance of the iris. The object is accomplished by including a portion of the iris in a ligature, and keeping it in con- tact with the external coats of the eve until adhesion IRIDDESIS. 45 has taken place between the two tissues. As perfect quiet on the part of the patient is very desirable, anaes- thesia should be induced preliminary to the operation. A puncture is made through the sclerotica at the extreme edge of the anterior chamber, with a broad needle. A loop of fine silk being laid upon the eye- ball, surrounding this puncture, the canula forceps is introduced, the iris seized near its ciliary margin, and drawn out through the wound. An assistant now takes hold of the two ends of the loop with two pairs of forceps, and ties it, including that portion of iris held in the grasp of the instrument. In two or three days the ligature, with the minute strangulated por- tion of the iris, falls, or may be removed, and the wound has been so small that the eye has usually almost perfectly recovered, even in this brief period. A greater or less amount of displacement may be obtained, according as more or less of the iris is drawn out and included in the ligature ; or, if necessary, two or more operations may be successively done, at differ- ent sides of the, pupil, to give to it the desired form and size. The noose of silk is not essential in this operation, as, if the wound be not too large, the iris will remain strangulated in it. But the use of the hVature leads to a quicker separation of the extruded bit of iris, and is therefore generally to be preferred. The safety of this operation and the quick recovery of the patients, are most important arguments in its favor. 46 RECENT ADVANCES IN OPHTHALMIC SCIENCE. CORELYSIS. A WELL-KNOWN consequence of neglected iritis is the formation of more or less extensive adhesions be- tween the margin of the pupil and the surface of the crystalline lens. Similar adhesions of the iris to the inner surface of the cornea may result from ulceration or wound. Formerly it was not the practice to interfere with these adhesions, except when they were of such ex- tent as greatly to impair vision. More recently, they have been regarded as a cause of recurrent iritis in eyes where they exist. To detach these adhesions, Mr. Streatfeild of London has proposed a method of operating, named by him corelysis, or pupil opening, which is well adapted to take the place, in a certain number of instances, of iridectomy, which had been strongly advocated in these circumstances by Yon Graefe. The only instruments required are a broad needle, and a fine spatula and hook mounted on the same handle. These instiniments should be of flexible met- al, so that they may be bent to any curve which may adapt them to different forms and situations of adlie- sion. Absolute quiet should be insured by the ad- ministration of ether. CORELYSIS. 47 A puncture is made with tlie needle, usually at a point of the cornea opposite to the principal adhe- sions, and the spatula or hook is introduced, if possi- ble, without the escape of the aqueous humor. It is then to be passed carefully behind the adhesions, the end of the instrument being kept as much as possible towards the iris, so as to avoid risk of wounding the capsule of the lens. The adhesions are then separated by slight lateral or tractile movements. After the operation, the iris should be put under the influence of atropia, to avoid re-formation of synechiae. In cases where the adhesions are of limited extent, and even where the pupil is occluded by false mem- brane, if merely its margin has become attached, this operation will compare favorably with iridectomy ; as by its means the normal central opening is re-estab- lished, leaving, perhaps, a certain amount of deposit upon the capsule of the lens, but placing the eye in more favorable conditions than when iridectomy has been done, inasmvich as the normal movements of dilatation and contraction of the pupil are preserved. 48 RECENT ADVANCES IN OPHTHALMIC SCIENCE. DISEASES ORIGINATING IN MORBID CONDI- TIONS OF THE SYSTEM. Much new information has been gained in regard to certain forms of disease, manifested in the eye, but depending on causes existing in the general constitu- tion of the patient. These mutual dependencies of disease have great interest, not only as facts in oph- thalmic science, but for the general practitioner, and instances often occur -svhere an acquaintance with their phenomena proves of the greatest advantage in rendering the diagnosis of various affections more cer- tain, and treatment more sure. EXOPHTHALMOS WITH ANJISHA. Apart from those cases where protrusion of the eyeball may be produced by direct causes, such as aneurismal or other tumors of the orbit, paralysis of the motor muscles, &c., it occurs as a temporary symptom in some patients, simultaneously with en- largement of the thyroid gland and with disease of the heart. The coexistence of these conditions has been so often observed that there can be no doubt of their mutual relationship. HEMERALOPIA. 49 Tills affection presents so formidable an aspect as to be startling and repulsive at first sight. But it is important to I'ecognize its true character, that we may be able to reassure the patient as to the prognosis, and to institute a treatment Avhich will insure its removal within a comparatively brief period. The symptoms subside under the use of tonics, without the necessity, as a rule, of a resort to local means. HEMERALOPIA. The connection of night-blindness with scorbutic conditions of the system, and the necessity for tonic general treatment, as well as of avoidance of its ex- citing causes (of which the principal is a long-contin- ued exposure to a glare of light to which the eyes have not been accustomed), was clearly established by observations made by English and French army sur- geons during the Crime.an campaigns. The subject has been interesting to our own army medical staff, as the affection has been of frequent occurrence at sta- tions in the extreme Southern States. A surgeon of the garrison at Strasburg in France has proposed what he claims to be a speedy and effect- ual method of cure, — by confining the patients in an entirely dark room for a considerable number of hours, — not allowing light to enter even for an instant. The eyes thus being left in complete repose, appear 50 EECENT ADVANCES IN OPHTHALMIC SCIENCE. to recover their tone and functions, and relapses are, as he asserts, quite rare after the seclusion has once been of sufficient duration. From this officer's account of his success, the method would seem to be pecu- liarly adapted to the exigencies of army service. Ton- ics and anti-scorbutics should, however, be liberally given as a security against relapse. An accomplished surgeon of our army informs me that a limited trial of the above system of seclusion did not give him the hoped-for results. He found no treatment eifectual except removal of the men from seaboard stations, where they were exposed to glare from white sand, to posts in the interior. The men of his command be- lieved raw liver of great advantage in relieving the attacks. RENAL DISEASE AS SEEN IN THE EYE. Nothing could once have seemed more marvellous than that we should seek in the eye a diagnosis of dis- ease of the kidney. Yet modern observations have furnished us with two most interesting examples of simultaneous pathological changes, in the connection which has been discovered between Bright's disease and certain alterations in the retina, — and between diabetes and one form of cataract. BRIGHT' S DISEASE. 51 BRIGHT' S DISEASE. It is no less true than remarkable that we are able, by means of the ophthalmoscope alone, to diagnosti- cate this disease of the kidney. A patient presents himself complaining of gradual loss of sight, but whose eyes present externally every appearance of health. On examination with the ophthalmoscope, the optic papilla and retina are seen to exhibit marked structural changes, peculiar to and characteristic of this disease. A slightly grayish opacity is visible in the optic nerve and over the retinal surface, with a marked alteration around the papilla and in the region of the macula lutea. This consists in a radiated whitish ap- pearance of the retina, which would seem to have undergone transformation. Small spots of extrava- sated blood are sometimes observed here and there in the retina. Post-mortem appearances indicate that the retina has become thickened and indurated by fatty and other deposits. Changes may also have taken place in the choroid and in the vitreous humor. In a more advanced stao-e, the white defeneration of the retina is sometimes replaced by atrophy. As we can never determine what may prove to be the value of a new pathological fact, the phenomena above described may, in the future, throw much light on the causes and progress of the yet more grave lesion with which they seem to be associated. 52 EECENT ADVANCES IN OPHTHALMIC SCIENCE. CATARACT IN DIABETES. The existence of cataract in diabetic patients has been from time to time noticed by different observers, and is now admitted to be more than a mere coinci- dence, and of very frequent occurrence. Generally it is developed only at a late period of the renal disease. These facts have assumed a new interest since the experiments of Dr. Mitchell of Philadelphia on the artificial production of cataract in frogs by injection of solutions of sugar into the sub-cxitaneous cellular tissue of these animals, — and the subsequent gradual disappearance of the opacity of the lens, in a portion of the cases. We cannot but hope that further ex- periment and observation may throw light upon the pathology of cataract, and possibly guide us in discov- ering some means of preventing or removing it, other than bv surgical interference. SEQUEL.E OF DIPHTHERIA. Among the various forms of paralysis which some- times follow diphtheria, we observe a loss of the power of accommodation of the eyes ; so that patients are unable to use them for reading or other purposes re- quiring close application. The loss of accommodation is usually accompanied by dilatation of the pupil. INHERITED SYPHILIS. 53 This affection is not to be confounded with diphthe- ritic inflammation of the eye, which will be elsewhere spoken of. As sequelre of diseases of this type often gradually disappear with the complete restoration of strength and health, it is difficult to determine the value of spe- cific remedies. But much apparent benefit has been obtained from the application to the conjunctiva of the extract of Calabar bean, by which the pupil is con- tracted and the ciliary muscle pei'haps excited to action. Tonic general treatment should be at the same time employed. INHERITED SYPHILIS. One of the most interesting and important among the modern contributions to ophthalmic science is found in the results of the observations of Mr. Hutch- inson, of London, in regard to the morbid conditions of the eye due to the influence of congenital syphilis. Cases of syphilitic iritis in infants had been recorded by authors ; but other and more frequent affections, of which those of the cornea form a large proportion, — althoucrh observed and described, — were not at- tributed to their proper source, but had been regarded as of strumous origin. Mr. Hutchinson pointed out the relations of these several affections to one another and to the general diathesis, and traced with a master hand various 54 RECENT ADVANCES IN OPHTHALMIC SCIENCE. marked features Avliich go to make up the complete physiognomy of the constitutional disease, whether developed early or cropping out some years after birth. INFANTILE SYPHILITIC IRITIS. The phenomena of infantile syphilitic iritis exhibit some peculiarities which are worthy of careful notice ; as the disease, contrary to what occurs in adults, is attended with few active symptoms, and often escapes notice during its curable stage. There is very little and very transient injection of the circum-corneal zone, or of the other vessels of the eye, and little or no pain ; but the iris becomes muddy looking and discolored, and lymph is in almost all cases effused from its surface, and especially into the field of the pupil. If seen early, before the pupil has become blocked up by deposits, the prognosis is favorable ; as there is every probability of obtaining a perfect recovery by taking measures to maintain dilatation of the pupil, and by suitable constitutional treatment. Even when considerable effusion has taken place, and the pupil has become partially obscured, there is reason to hope for a favorable result if proper means are used ; as in these young subjects absorption of the morbid pro- ducts often takes place to a surprising extent. SYPHILITIC KERATITIS. 55 SYPHILITIC KERATITIS. Unlike the disease of the iris resulting from intra- uterine contamination, the affection of the cornea attributable to the same origin rarely makes its ap- pearance till the period of second dentition. It had been regarded as a manifestation of strumous diathe- sis, and its symptoms described as such by authors who had well observed its characteristic features ; but there seems to be no doubt as to its affiliation with other unquestionable evidences of syphilitic saturation. At the outset, as in infantile syphilitic iritis, there is little pain, and scarcely any injection of the vessels of the eye. But much dimness of vision is complained of, and on examination the cornea is observed to be more or less thickly sprinkled with minute dotted opacities- These are evidently not upon its anterior surface, but diffused interstitially through its sub- stance. If examined with a lens they are seen to be infinitely multiplied. As the disease advances, not only the central portion, but even the entire cornea may become obscured, and acquire a cloudiness re- sembling the opacity of ground glass ; but there is little tendency to ulceration. Sometimes, at this stage of the disease, the globe is much softened, so as to be even flaccid when pressed with the finger. Accompanying this increased cloudiness of the cornea there is often considerable injection of the vessels of the circumcorneal zone, and sometimes iritis compli- 56 RECENT ADVANCES IN OPHTHALMIC SCIENCE. cates tlie affection, or traces of its having occurred during infancy can be detected if sought for. It is the rule that tlie disease affects in turn the two eyes, — the second being perhaps attacked whilst the first is recovering. All cases of sluo;o;ish keratitis of this diffused char- acter, occurring in subjects from six to eighteen years of age and unattended by ulceration or by much pain or photophobia, should be viewed with suspicion, and inquiry made, if possible, as to the antecedents of the parents, and the family history. If the child had, during its infancy, any syphilitic symptoms, in the eye or elsewhere, — if the mother has had still-born chil- dren or such as had but a puny and brief existence, — if others of the brothers and sisters have suffered from similar affections, — it would be desirable to ascertain if either parent has had symptoms of constitutional syphilis. But we are not compelled to rely solely on this knowledo-e for corroborative evidence, however satis- factory it may be thus to obtain it. In most instan- ces, we find in the patient other diagnostic marks, which serve as so many manifestations of a pervading infection. The most distinctive of these are found in the condition of the teeth and the skin. As Mr. Hutchinson has well pointed out, the central incisors of the second dentition have a peculiar crescentic notch at their lower margins, and the lateral incisors and canines, as well as the molars, are often small. SYPHILITIC KERATITIS. 57 peg-sliaped, and with tubercular prominences upon their surface. They are perhaps also irregularly set in the jaw, and of bad color or prematurely de- cayed. The following plates show these abnormal appear- ances as exhibited in three cases now under my obser- vation. Fis. 12. Fig. 13. Fiff. 14. Figures 12 and 13 show the con- dition of the teeth in a boy and girl aged about twelve and fourteen. In figure 14, fi'oni a girl of seventeen, the notched appearance has already be- come lessened by wear of the teeth. The skin is coarse and sallow, often pitted in a sin- gular manner, — the bridge of the nose usually broad and sunken, — there are cicatrices of fissures at the angles of the mouth, — and the lips are thick and misshapen. As in the acquired syphilis of adults, the choroid and retina, as well as the iris, are sometimes impli- cated, generally simultaneously with the corneal affec- tion, and effusions occur in those parts, especially in the choroid. This fact should be borne in mind Avhen 3* 58 RECENT ADVANCES IN 0PHTHAL:\IIC SCIENCE. treating this affection, as the opacity of the cornea frequently makes it impossible to examine the fundus of the eye with the ophthalmoscope. Mr. Hutchinson has advised, — and in this he is sustained by other authorities, — a combination of tonic with mild mercurial treatment, — the patient be- ing usually in a cachectic condition. The prognosis is generally favorable, — the tissues, if not too deeply implicated, slowly regaining their normal condition. Even where softening had become exceedingly marked, with a tension of — 3 degrees, I have seen recovery take place. We may, therefore, if well satisfied of the correctness of our diagnosis, confidently reassure the patient, even when, from the increasing dimness of vision, the future seems to him very hopeless. But in some cases, of more than average severity, the clearness of the central part of the cornea is not restored till after a period of years. SYPHILITIC DISEASE OF THE EETINA IN ADULTS. Changes characteristic of this diathesis are some- times observed in the retina in conjunction with syph- ilitic iritis, and they may occur independently of this. Under the ophthalmoscope the retina shows a very slight diffused, clouded appearance, as if infiltrated, — or sometimes so considerable a change that the outline of the optic disc cannot be distinguished from the surrounding parts, together with, in most cases, waxy- SYPHILITIC DISEASES OF THE RETINA. 59 looking opacities extending irregularly outwards from the regions of the optic disc and the macula lutea. These differ materially from the strongly-defined alter- ations of color and structure observed in B right's dis- ease. Spots of hemorrhagic effusion are also now and then to be noticed. Little or no pain is com- ])lained of. The morbid appearances are usually amenable to treatment, and vision may be in a good measure or even fully restored in patients whose symptoms had reached an extreme degree. Other cases, however, are less tractable, and where the con- stitution is utterly broken by the syphilitic cachexia curative means are sometimes unavailing to arrest the disease before the sight has undergone irreparable injury. As in congenital syphilis of the eye, the best treat- ment of these cases is a combination of tonic and spe- cific measures. Among the latter, mercurial inunc- tion seems to deserve prominence. From the tendency to plastic effusions, it is gener- ally desirable to make use of atropia to dilate the pu- pil, if any implication of the iris should be observed during the course of the retinal affection. GO RECENT ADVANCES IN OPHTHALMIC SCIENCE. SYMPATHETIC INFLAMMATION OF THE EYE. Within a few years, the fact that after injury of one eye the other may be aflfectecl with a pecuhar form of sympathetic inflammation, has been more generally recognized. The liability to this morbid action seems to be great- est in cases where one eye has been roughly torn open, or where a foreign body has penetrated and re- mains within it, — and, especially, Avhere the injured eye has continued sensitive and irritable after recovery from the first effects of the accident. It does not fol- low incised Avounds made in the operations for cata- ract or iridectomy, or the loss of an eye in conse- quence of purulent inflammation. The s} mptoms do not immediately supervene upon the injuries which give rise to them. On the con- trary, the Avounded eye, especially if it retain within it a bit of steel, percussion-cap, or other foreign sub- stance, often apparently recovers from the inflamma- tion which follows the accident, and may remain for some time in a perfectly quiescent state, though with diminished sight. But after thus continuing quiet for many months, fresh symptoms arise, the eye becomes again injected and painful, and suppuration perhaps SYMPATHETIC INFLAMMATION OF THE EYE. 61 commences around the foreign body, to effect its elimi- nation by bringing it gradually towards the surface. It is during these processes that danger of sympa- thetic inflammation is to be apprehended. Should the symptoms be violent or protracted, an effort ought to be made, without too long delay, to discover and extract the offending substance ; or the globe should be at once removed ; according to the circumstances. In other instances, where the eye has been wounded, instead of becoming quiescent for a time, it continues in a state of low inflammation, — never wholly free from pain and injection. This condition of irritability is especially dangerous to the safety of the other eye. The beginning of sympathetic inflammation is indi- cated by a gradual diminution of vision in the best eye, and this is followed, if the disease is not arrested, by a peculiar dull, infiltrated aspect of the iris, and, finally, by an effusion of lymph, closure of the pupil, and partial atrophy of the globe ; these changes being often accompanied with considerable pain in and around the eye. The ophthalmoscope discloses con- gestion of the optic disc, and, later, if the view of the fundus is not cut off by the effused lymph, more seri- ous changes there and in the retinal tissue, extending subsequently to the choroid and iris. The only reliable means of arresting this formid- able disease is the removal of the injured and useless globe ; (unless there is reason to believe that the source 62 RECENT ADVAXCES IX OPHTHALMIC SCIENCE. of irritation is situated in the ciliary region, in which case excision of the anterior half of the eye may pos- sibly suffice ;) as its presence constitutes an insidious source of mischief to the other eye, which no remedies can counteract. Tliis proposition is startling to the patient, — who is reluctant to believe that an eye which has been injured months, or even years pre- viously, and which, i)erhaps, at the time, is free from morbid phenomena, can be the cause of symptoms which appear to him of trivial importance. But it cannot be too gravely and imperatiA'ely insisted on, for delay annuls the chances of success, and the patient, forced at last by his increasing blindness to consent to any measure proposed for his relief, finds the means which, earlier employed, might have saved his eye, wholly unavailing. Care should, however, be used not to hastily sacri- fice every eye which has suffered a considerable in- jury, even when the ciliary region is involved, as such an irreparable loss must not be needlessly inflicted. Should the second eye exhibit much congestion or other change in the internal parts on ophthalmoscoj)ic examination, it may be necessary, after the removal of the injured eye, to resort to local depletion from the temple, near the remaining eye, by means of leeches or Heurteloupe's instrument, and to employ such general treatment by derivation or otherwise as may seem adapted to the relief of the local condition. Should the symptoms continue, iridectomy would be indicated. ENUCLEATION OF THE EYEBALL. 63 ENUCLEATION OF THE EYEBALL. As performed before the clays of anaesthetics, the removal of the eyeball was a truly formidable pro- cedure. Now, and especially in the improved mode of doing it, the operation may be regarded as one of the most trivial. The conjunctiva is divided, close to the edge of the cornea, on the side towards the inner canthus, and one or two of the recti-muscles are cut. Curved scis- sors are then carried behind the globe, and the optic nerve severed ; after which the eye may be turned out of its socket and the remaining muscles and por- tion of conjunctiva cut away, close to the globe. The eyeball only is thus removed, leaving the fibrous cap- sule in which it revolves, with its muscular attach- ments, to form a sort of stump or cushion for the sup- port of an artificial eye. The hemorrhage which ensues may be readily controlled by placing a piece of sponge in the orbital cavity and applying com- presses and a bandage. After twenty-four hours these dressings may be re- moved, and cold wet compresses applied for a day or two longer, at the end of which time recovery is com- plete or nearly so. 64 RECENT ADVANCES IN OPHTHALiOC SCIENCE. GLAUCOMA: ITS TREATMENT BY IRIDECTOMY. To have devised an efficient remedy for a hitherto incurable disease is certainly no mean achievement. Such was the happy fortune of Professor Von Graefe, in applying the operation of iridectomy to the cure of glaucoma. The subject is of such importance, the diagnosis of this affection, in its early stages at least, is yet so ill understood by the majority of general practition- ers, and the necessity for prompt interference is so urgent, that an account of the characteristic features of the disease will not be out of place in this con- nection. Since the invention of the ophthalmoscope all the phenomena of this disease have been examined de novo, and we now know that the appearances, espe- ciall}' the sea-green opacity of the pupil, which for- merly constituted our sole means of recognizing and gave a name to the affection, are but symptoms of a far advanced stage of the malady. Those attacked are usually beyond middle age, and a large proportion are females who have passed the critical period of life. Deterioration of the general health, especially when combined with the depressing influences of fatigue GLAUCOMA: ITS TREATMENT BY IRIDECTOMY. 65 from watching with sick friends or grief at their loss, appears to be frequently a predisposing cause. But the disease may exceptionally occur in those whose health is unimpaired and who have endured no men- tal anxiety. It is also in some cases hereditary. Both eyes are usually attacked, at an interval which varies from a few days to as many years. The friends of a patient in whom one eye has been affected should therefore be warned to lose no time before ap- plying for aid, should any symptoms, however slight, declare themselves in the other eye. But this warn- ing should not be expressed to the patient, as it would but serve to fix the attention upon the eye and possi- bly might predispose to an attack. Even a necessity for a rapid increase in the power of spectacles, if such are worn, should not be allowed to pass unquestioned, as this is one of the premonitory symptoms. If ac- companied by appearances of rainbow colors around a lamp, or flashes of light within the eye, and, espe- cially, if the patient complain of occasional transient attacks of indistinctness of sight, it should induce fur- ther inquiry, to ascertain if tension of the globe, in any abnormal degree, is present, — or if limitation lias taken place in the field of vision. Should these symptoms be overlooked or under- valued, the patient's vision may, in chronic cases, be gradually lost, if only one eye be affected, without the occurrence of any severe pain, or injection of the ex- ternal vessels, to call attention to the eve. If, on 66 RECENT ADVANCES IX OPHTHALMIC SCIENCE. examination by the toucli, the eye gives to the finger a sensation of increased resistance, indicatinoj abnor- mal tension, it should be examined with the ophthal- moscope to determine if further evidence of intra- ocular pressure is to be found in a cupped condition of the optic nerve. The advantages of iridectomy are not, it is true, as marked in the chronic as in the acute form of glau- coma, — and frequently, especially if the symptoms have been of any considerable duration, the most which can be hoped for is to prevent further lessen- ing of the patient's vision ; but if, with this result, he can hope for greater security from attack in the other eye, as there is some reason for believing, the surgeon is fully justified in advising an operation which in- volves almost no risk, pain, or loss of time. After a longer or shorter duration of the more pas- sive morbid processes, a sudden explosion of violent Symptoms may occur, and the case assumes the char- acters of acute glaucoma. Here the performance of iridectomy is urgently demanded, not only to preserve if possible any visual power which may yet remain, but to relieve the intense suffering. The onset of acute glaucoma is as overpowering as the invasion of its chronic form is insidious. In- stantly, in some cases, severe pain is felt in the eye, which augments till it becomes agony. It extends to the supra-orbital region, and even affects the brain. Frequently it causes sympathetic disturbance of the GLAUCOMA: ITS TREATMENT BY IRIDECTOMY. 67 stomach, with intense nausea and vomiting. Exami- nation of the eye shows a varicose turgescence of the sub-conjanctival vessels, Avith perhaps more or less cir- cum-corneal injection, a bluish tint in the sclerotica, and a certain amount of chemosis. The cornea has a dull aspect, and has lost its sensibility, so that it may be touched without giving pain. The iris is evidently crowded forward, rendering the anterior chamber shal- low, and the pupil is expanded, by pressure of the lens. The pupil does not contract under the influ- ence of light, and its field is muddy, allowing a less distinct view of the fundus than can be had in a healthy eye. Often the fundus cannot be made out with the ophthalmoscope. If seen, the optic disc is observed to be pushed backwards by the distending fluids of the globe, and the retinal vessels follow this altered direction of its surface, emerging from it as if passing over the edge of a cup ; their continuity ap- pearing broken. Pulsation of the retinal arteries and a beaded vari- cose enlargement of the veins, may in some instances be observed, showing the obstruction which exists to a free circulation within them. Greater or less changes in the choroid or retina may also be present. The eyeball is of almost stony hardness to the touch, especially after the symptoms have been of some little duration. If objects continue to be perceived, they aj)pear white or as if seen throuo;h a fog. 68 RECENT ADVANCES IN OPHTHALmC SCIENCE. Unhappily tliere are too many cases where tlie disease is not at first recognized ; the severe pain and loss of vision being attributed to neuralgia, and the other evidences of disease in the eyeball being quite overlooked, since they are not so marked as to attract attention unless carefully observed. It is thus only at an advanced period of the disease, when hope- lessly irreparable transformations have taken place, that it is discovered that somethino; is wrono; in the appearance of the eye, and the case is referred for con- sultation to a practitioner of experience in ocular dis- eases. The cornea is now still more dim, and its epi- thelial layer is sometimes raised as if vesicated. The pupil has become so widely dilated that the iris, atrophied and disorganized, forms merely a thin and narrow ring. The lens presses so far forwards as nearly to obliterate the anterior chamber, and has become opaque and acquired a dirty sea-green color. The deeper pai'ts of the e^^e can no longer be ex- plored with the ophthalmoscope. Externally, the sclerotica has a thinned bluish look, and several large vessels run between it and the conjunctiva, anastamo- sing around the cornea. The excessive hardness of the globe, as if a marble were under the eyelid, con- tinues in most cases ; but the intense suffering accom- panying the period of active distension is now, per- haps, abated, — the nerves having as it were adapted themselves to their altered conditions of tension. In some instances, however, pain still lingers to GLAUCOMA: ITS TREATMENT BY IRIDECTOMY. 69 such a degree that iridectomy and extraction of the lens are demanded for the patient's comfort ; though of course without hope of restoring vision where all perception of light has been for some time lost. The best explanation hitherto given of the origin and course of this mysterious disease, is that of Professor Donders of Utrecht, who believes it to have its source in an irritation of the ciliary nerves, Avhich preside over the secretion of the vitreous humor. In consequence of this neurosis the vitreous becomes increased, and tliis augmentation, by producing general distension of the globe, presses upon the nervous filaments and adds to the already existing derangement of their functions. The morbid phenomena thus act and react upon each other, and the disease goes on from bad to worse. This theory also well explains the mode in which re- lief may be afforded by the operation of iridectomy. Excision of a portion of the iris as far as its ciliary attachments, attended as it necessarily is by evacua- tion of the aqueous humor and a certain amount of depletion from the torn vessels, may act in two ways : by directly reducing the intra-ocular pressure, and by lessening the tension and irritability of the ciliary nerves and favoring a restoration of their normal action. That the last of these effects is that of chief remedial importance is proved by the fact that mere evacuation of the aqueous, though several times re- peated, seems to be almost without influence on the course of the symptoms. But, whatever theory may 70 KEGENT ADVANCES IN OPHTHALMIC SCIENCE. be entertained as to the cause of the disease, or the modus operandi of the operation wliich relieves it, we have the gratifying assurance of possessing in iridec- tomy a safe and effectual cure, the value of which has become so rapidly and so generally acknowledged, as, within a few years of its first performance, to have nearly superseded all other treatment, medical or surgical, of this disease. The means formerly em- ployed were conceded to be powerless to control this formidable affection ; and another proposed operation, section of fibres of the ciliary muscle, has failed of acceptance, to any extent beyond the immediate circle of its origin. I refer to my previous description for the details of iridectomy, merely remarking here that at least a sixth of the iris, generally at its upper por- tion, should be excised in glaucoma. The prognosis is almost always favorable, in acute cases, if seen Avithin a few weeks of the onset of the disease, provided too extensive structural alterations have not taken place ; — even where the pain has been intense and little more than a perception of light remains. Should the organic changes be inconsiderable, suc- cess should not be despaired of, even after some months' duration of the disease and loss of perception of light, — instances of recovery having occurred where the conditions where thus unpromising. But the progress of pathological change is oftentimes so ra[)id, that no delay is admissible after the diagnosis is GLAUCOMA : ITS TREATMENT BY lEIDECTOMY. 71 once fully made out, — a few clays or even a few hours frequently changing the entire aspect of the case, and rendering an eye which might with almost certainty have been saved utterly incurable. The disease, in these instances, seems to destroy the vital- ity of the organ almost as rapidly and fatally as the stroke of lightning extinguishes animal life. As soon, therefore, as well-marked symptoms have declared themselves, the operation should be at once urged upon the patient. The extreme danger attending delay may be represented to him, — and he may be at the same time assured that the operation involves no risk, and, if done at the upper part of the iris, a scarcely perceptible deformity ; — while he can be almost sure of inestimable benefit. The tunics of the eyeball having been so greatly distended, there is, in a few instances, delay in obtain- ing union, owing to the bulging outward of the lips of the wound, and the scar, when formed, is at first thin, and has for a time a tendency to give way. But this merely protracts without seeming otherwise to in- terfere with the restorative process ; though it should induce caution as to premature exposure. As a rule, however, a few days' confinement to a moderately darkened room suffices for cicatrisation of the wound. The eyes should be bandaged, with moderate com- pression, for two or three days at least, but beyond this no local or general treatment is usually re- quired. 72 EECENT ADVANCES IN OPHTHALMIC SCIENCK The intense pain is at once relieved bj the opera- tion ; but in a few cases a slight amount of pain and considerable sensitiveness to light, with a certain degree of tenderness on pressure, continues for some days subsequently. A wonderful improvement in vision is frequently observed within a few hours after the operation, even where sight had been apparently ex- tinct ; in other cases, the tension of the globe seems to be more gradually lessened, and perception is restored Avith corresponding slowness. The full benefit of the operation is often reached within two or three weeks ; though sometimes a longer interval must elapse before its attainment. The ophthalmoscopic appearances improve rapidly after the first days. The vessels of the retina regain their normal position and calibre, and the cupped asjJect of the papilla becomes gradually effaced. Similar changes for the better occur in the other parts which had begun to assume unhealthy aspects, — the morbid phenomena gradually receding till the normal condition is re-established. Usually, convex glasses are required after the oper- ation, and sometimes a patient has little near or dis- tant vision except by their aid, — even requiring those of very high power. APOPLEXY OF THE RETINA. 73 APOPLEXY OF THE RETINA. From the fact that the vitreous mass forms the only- support of one of the surfaces of the retina, we miglit anticipate tliat hemorrhagic effusion from the retinal vessels w^ould not unfrequently happen. Its occur- rence is, however, rare. It is now and then met with in patients who have disease of the heart, or in whom the menstrual or other periodic discharge has been suppressed, and may be seen in some instances where persons have had apoplectic attacks from which they have re- covered, or may occur in persons seemingly in good health, as a consequence of sudden exertion. In some cases, especially those connected with other apoplectic manifestations, small ecchymoses, having a flame-like appearance, are seen with the ophthalmo- scope, in different parts of the retina ; — in other in- stances, especially where unusual exertion has been the proximate cause, the effusion forms a uniform clot spread over a considerable surface. The symptoms vary, corresponding with the appearances. Where the extravasations are numerous but of small extent, vision is diminished, though not lost, throughout the entire field ; where, on the contrary, a single clot has been formed, the other portions of the retina may per- form their function, but the patient will be conscious 4 74 RECENT ADVANCES IN OPHTHALMIC SCIENCE. of a dark spot, of greater or less dimensions, in liis visual field, so that, in certain directions, objects or parts of objects are invisible. These effusions may gradually disappear, leaving the retinal tissue apparently uninjured and vision per- fect ; or some portions of the clot may remain and be- come organized, interfering more or less with sight. The treatment should be in accordance with the presumed cause, — every effort being made to avert any fresh outpouring, and to obtain the absorption of the blood already extravasated. Local remedies are in most cases of less value than derivative and consti- tutional measures. HYPERESTHESIA AND ANEMIA OF THE RETINA. Hyperesthesia is marked by fulness of the retinal circulation, with greatly augmented sensibility to light, and is often attended with extreme contraction of the pupil. We find it most often in debilitated or hyster- ical subjects. Tonic general remedies should enter largely into the plan of treatment employed, though they are to be assisted, at the outset, by moderate local depletion and by stimulating pediluvia to relieve the congested vessels. The patient should not be allowed to remain secluded from the light ; nor, on the other hand, sub- SEPARATION OF THE RETINA. 75 jected to sudden forced exposure. A sliade, or deeply- colored glasses, or both, may be allowed, until such time as their use can be comfortably dispensed with. Anaemia of the retinal circulation, as also leucocy- themia, cyanosis, and the formation of earthy and bony deposits in the retina, have been occasionally met with, but are rare. Complete obliteration of the arte- ries and veins proceeding from and returning towards the optic disc is sometimes observed, a few white lines, like fine threads, only remaining to indicate the situation once occupied by the yessels. SEPARATION OF THE RETINA. This pathological change, unfortunately extremely frequent, results from an effusion of serous fluid be- tween the retina and the choroid. The exudation most often occurs at the upper portion of the retina, but soon finds its way by gravitation to the lowest seg- ment. It may remain of limited amount, or may in- crease so as to detach the entire retina from its con- nection with the choroid. When the separation has reached this extreme degree the retina forms an infundibulum, retaining -its attachment around the op- tic entrance, but everywhere else thrown into folds which float and roll upon each other with each move- ment of the eye. 76 RECENT ADVA>;CES IN OPHTHALMIC SCIENCE. The appearances exhibited at this advanced stage are often visible to the naked eye, especially if the pupil has been dilated, — and can be readily seen by the aid of lateral illumination. Viewed with the ophthalmoscope, in the earlier de- grees of the affection, the separated portion presents a slightly grayish translucent surface, evidently raised above the surrounding portions of the retina. When more detached, it assumes the form of irreg- ular folds bulging forwards towards the iris, and may often be best seen with the mirror of the ophthalmo- scope w'ithout the lenses. These appearances should not be mistaken for the rollino; masses of disor";anized hyaloid membrane, sometimes containing crystals of cholesterine, which are now and then observed, and which offer at first sight a not dissimilar aspect. In some cases the two affections are concomitant, — sep- aration of the retina occurring as a sequel to disease of the vitreous, — being drawn away from its normal position by contraction of that mass. It is also liable to take place as a consequence of posterior staphy- loma, in cases of progressive myopia, — the thinned sclerotica and choroid receding from the retina and allowing of sub-retinal effusion, at first only to the ex- tent of the staphyloma, but afterward spreading by infiltration over a larger space. The treatment by enforcing perfect quiet, the pa- tient lying on his back, as practised by Professor Don- ders, seems to have been successful, in young subjects, CHOROIDITIS. 77 in effecting absorption of the fluid, and reapplication of the retina to the choroidal surface. Professor Von Graefe has proposed incision of the separated portion, by means of a very minute knife passed into the eye- ball behind the crystalline lens and carried towards the centre of the separated surface, and Mr. Bowman has practised a laceration of the retina with two nee- dles. The results of these operations have' afforded some encouragement to at least a further trial ; espe- cially in the early stages of the affection, before the retina has become extensively displaced by a large accumulation behind it. CHOROIDITIS. Apart from the implication of the choroid with the retina, in some cases of secondary and of inherited syphilis, and from the changes which take place in posterior staphyloma, this membrane is liable to become the seat of exudation or of disseminated inflammation. As seen by the ophthalmoscope, spots which have been the seat of exudation present whitish patches generally surrounded by a border of aggregated pig- ment cells. In some of these patches little of the choroidal tissue remains, the whitish reflexion coming from the denuded sclerotica. 78 RECENT ADVANCES IN OPHTHALMIC SCIENCE. During the presence of disseminated inflammation of tlie choroid, the vitreous, which seems intimately con- nected with it, loses in a degree its transparency, and often becomes pervaded with flocculi. The fundus of the eye is then indistinctly seen. A strong tendency exists, in one form of this dis- ease, to effusion of thin serous fluid, and this fluid, frequently holding pigment globules in solution or capable of producing them, finds its way through the retina aloncr the course of its vessels, giving rise to secondary disease of that membrane and to the forma-' tion of pigment deposits there, and causing atrophy of its tissue and of its nutrient vessels from pressure. This affection, sometimes termed retinitis pigmentosa, has been attributed by Liebreich and other observers to consanguinity of the pai*ents of the subject ; though this has not been recognized as a predisposing cause by other authorities. Its symptoms begin in early life, — vision being defective, especially in a feeble light. The deficiency of power, and limitation of the field of vision increases with age, and at or before middle life total blindness supervenes. Thus far all treatment has proved unavailing. Simple choroiditis may become resolved, and the alterations to which it has given rise may in a great measure disappear ; but more frequently — and this is especially true of its syphilitic form — choroiditis is the occasion of such changes of contiguous parts, of the ret- ina or vitreous, that complete recovery is not obtained, POSTERIOR STAPHYLOMA. 79 and some limitation, at least, of the field of vision re- mains. Even in favorable cases progress must be slow. The most approved treatment consists in a resort to local depletion and the internal administration of bi- chloride of mercury in small doses. Other derivative means should at the same time be employed. The performance of iridectomy, especially in acute attacks or where the pressure of transfused fluid has increased the tension of the globe, is also sometimes of the great- est advantage. It should always be done, in these cases, unless for urgent and special reasons, in the upper portion of the iris, that the patient, after re- covery, may be spared the dazzling caused by enlarge- ment of the pupil downwards. POSTERIOR STAPHYLOMA. Thinning and giving way of the tunics of the eye- ball may occur at any part of its surface, as a result of disease. But we are indebted to modern re- searches, in aid of which the ophthalmoscope and post-mortem examinations have borne a prominent part, for a knowledge of the fact, that such a condition is extremely common around the entrance of the optic nerve, — that it may commence and increase Avithout a suspicion of its existence being for some time ex- 80 RECENT ADVANCES IN OPHTHALMIC SCIENCE. cited, — and that it is very frequently both a conse- quence of myopia and a cause of its increase. The protrusion backwards of this portion of tlie eye- ball (regarded by some writers as the result of inflam- matory action, and termed by them sclero-choroiditis) begins, so far as we can perceive by observation, by an attenuation of all the tissues, especially of the sclerotica and choroid. As shown by the ophthalmo- scope, it has the form of a .whitish or grayish-white crescent, its concave edge towards the optic disc and its convexity in the direction of the macula lutea. As the affection progresses, the crescent becomes wider and more prolonged, sometimes completely encircling the disc, but expanding principally towards the yellow spot ; its outline at the same time becoming more irregular. The reflection from its surface grows whiter as attenuation and atrophy of the choroid and retina goes on and the sclerotica becomes more and more exposed ; though its surface may be studded with grayish spots, remains of the choroid, or with lilack pigment accumulations. The retina is thinned and expanded ; but its nerve fibres are for a long time unaltered, so that impressions made upon other parts of the retina are still conveyed across this space, though no clear images can be formed upon the im- plicated surface. As the sclerotica yields more and more, the devious course of the retinal vessels shows that they run over a concave surface. Other spots of atrophy of the choroid often make their appearance POSTERIOR STArHYLOMA. 81 near the margin of the crescent or in the vicinity of the macula lutea, and coalesce with the extending staphyloma, giving it an irregular instead of a cres- centic form. The disc seems oval instead of round, as the side of the optic nerve next the staphyloma be- comes involved in it. As the disease begins to affect the region of the yellow spot, or the optic nerve itself, vision becomes more impaired. With the increased bulging of the sclerotica the danger arises that the retina may not accommodate its surface to that of the outer tunic, and that effusion may be formed between the two structures, giving rise to the condition known as separation of the retina. That such abnormal elongation of the eyeball should be a cause of myopia niay be readily seen, — the lengthening of the optic axis giving rise to excess of refraction, so tliat the focus is formed in front of its normal position. But the affection, itself a cause of myopia, may be yet further increased in consequence of it. Any long-continued convergence of the optic axes, in accommodation for near objects, causes greater external pressure upon the globe from the action of the recti muscles, and at the same time the stooping position of the head assumed in reading and writing favors congestion of the vessels and increases the in- tra-ocular pressure. Both these influences promote the further yielding of the already weakened tissues, and thus lead to an increase of the staphylomatous bulo;inop. 4* I- 82 RECENT ADVANCES IN OPHTHALMIC SCIENCE. An examination of the fundus oculi with the oph- thalmoscope should therefore be made in all cases of short-sightedness, particularly in young subjects ; as it is important to detect the existence of staphyloma, if present, that precautions may be taken against its in- crease with the advancing age of the patient. During the period of youth there is a strong predis- position to an augmentation of this morbid change, and, unless counteracted, it attains such a degree that the eye becomes incompetent to oppose its steady march, and before middle age the patient has the mis- fortune to perceive, not only an increased myopia, but a constantly foiling vision. But if the period of youth can be safely passed without the development of progressive staphyloma, these results are less to be apprehended. It therefore becomes exceedingly im- portant to direct the patient to avoid everything which might favor the advance of this lurking enemy. Long- continued close application of the eyes, especially witli the head bent forward, should be interdicted, — glasses should be properly selected to avoid the necessity for accommodative eflPorts, — and every care taken, by de- rivative measures if necessary, to avoid cerebral or ocular congestion. catakact; its early diagnosis. 83 OPACITIES IN THE VITREOUS HUMOR. Where disease of the retina and choroid has ex- isted, especially if this has been of syphilitic origin, the ophthalmoscope sometimes brings to light fixed or floating opacities, of various size, in the vitreous mass, which seem to be the result of extension of inflamma- tory action to the hyaloid membrane. According to their size they interfere more or less with vision, having the appearance of muscae or of larger dark spots before the eye. They sometimes disappear as the primary disease subsides ; but where the vitreous has become extensively disorganized they remain, and frequently cause great imperfection of sight. Crystals of cholesterine may also occasionally be seen in the vitreous, and do not necessarily involve serious impairment of vision. CATARACT: ITS EARLY DIAGNOSIS. By means of the ophthalmoscope, and by oblique illumination, we are able to detect the presence of minute opacities of the lens at a much earlier stage of the disease than that at which it was possible to do so by the former methods of investigation. With the ophthalmoscope these are seen as shadows 84 KECENT ADVANCES IN OPHTHALMIC SCIENCE. thrown upon the fundus of the eye, and with a little practice are readily distinguished from dusky appear- ances haAJng their seat in the vitreous or in the cor- nea. By lateral illumination they gWe a grayish re- flection as light is thrown upon them, and are evi- dently situated but a little posterior to the iris. No hesitation need now be felt as to'Avhether we have to do with incipient cataract or with some more deeply-seated affection, and we are able to undertake treatment of these latter, in their early stages, with promptitude and confidence, instead of doubting, as formerly, whether the symptoms might not depend on commencing cloudiness of the lens which was as yet imperfectly developed. OPERATIONS FOR CATARACT. Among the numerous recently proposed modifica- tions in the operations for cataract there are some of unquestionable value. Extraction is now almost universally acknowledged, by scientific oculists, as the mode offering the best ultimate result, in cases of hard or semi-hard cata- ract. Extraction has been rendered more easy and its risks lessened by the introduction of anaesthetics. It is desirable, however, where these have been adminis- OPERATIONS FOR CATARACT. 85 tered, that the dressings should be promptly applied to the eyes, in order that the wound of the cornea may not be disturbed in case nausea and vomiting should supervene. Where such precautions have been taken no ill consequences result from etherization. It is an advantage, in this operation, that the globe should be fixed by being held with forceps dnring the section of the cornea. This is especially desirable, in fact almost indispensable, where ether has been given. The globe is thus prevented from retreating before the knife, Avhich can be carried steadily forward to form a smooth and regular flap. Furthermore, as the patient is unconscious, no contraction of the recti muscles is excited, and the danger of expulsion of a portion of the vitreous is thus greatly lessened. OUT-SCOOPING OF CATARACT. The out-scooping of cataract, by means of spoons devised for that purpose by Dr. Waldau (formerly Dr. Schuft) of Berlin, or by these spoons as modified by Mr. Critchett, is a modus operandi adapted to some cases of semi-hard cataract. In doing this operation a very broad, lance-shaped, bent knife is substituted for the ordinary extraction knife. The lids being separated by a spring elevator, and the eyeball turned downwards by means of for- ceps held by the operator or assistant, the knife is in- 86 RECENT ADVANCES IN OPHTHALMIC SCIENCE. serted near the upper edge of the cornea and pushed onwards, parallel with the iris, to the full breadth of the instrument. A portion of the upper part of the iris is now excised, in the usual mode of doing iridec- tomy ; but it is not important, as Avhen operating for tlie relief of glaucoma, that an entire segment of iris should be removed as far as the ciliary margin. All that is now needed is, that an enlargement of the pupil should be made, so as to afford more room for the extraction of the lens without exposing the iris to danger of contusion from the scoop. The third step of the operation consists in veiy free division of the anterior capsule of the crystalline, with one of the small instruments designed for this purpose. The thin scoop or spoon as modified by Mr. Critchett, or as in another model which I have devised and pre- fer, is then passed behind the lens, gliding along its convexity, if possible between it and the posterior capsule, care being taken not to rupture the hyaloid membrane, and is carried as far as the lower mar- gin of the crystalline. The spoon is then pressed slightly towards the cornea, and withdrawn, bringing with it the nucleus or a considerable portion of the lenticular substance. It is to be again introduced and withdrawn, till all fragments of crystalline, so far as seen, have been removed and the field of the pupil is clear. Care should be taken that fragments are not pushed behind the iris, to cause subsequent irritation, and that pressure is not made against that mem- brane. IRIDECTOMY TREVIOUS TO EXTRACTION. 87 This operation offers the advantages of a straight and small incision, well disposed to immediate union ; it lessens also the risk of prolapsus iridis, and we thus avoid two of the principal dangers of ordinary extraction. The recovery, in favorable cases, is more rapid, and the after treatment requires less strict care. These are strono- arfruinents in its favor. On the other hand, the objections to this method are, that inflammation of the iris and capsule, arising either irom contusion or from the presence of some unre- nioved fragments of the lens, are unhappily frequent, and that secondary operations for the removal of opaque capsule are often required. Its true relative value remains to be determined. IRIDECTOMY PREVIOUS TO EXTRACTION OF CATARACT. The operation of iridectomy as preliminary, and some weeks previous to extraction of the lens, has been recommended by Mooren and others, as calcu- lated to increase the chances of success. Only a nar- row strip or segment need be removed, — the design being to enlarge the natural pupil and thus obtain more room for easy exit of the lens, and also to lessen the chances of prolapsus iridis through the wound of tiie cornea. If this auxiliary operation be resorted to, iridectomy and the subsequent extraction should be done up- wards. 88 RECENT ADVANCES IN OPHTIIALMIC SCIENCE. Iridectomy may also be combined with extraction, — as proposed by Jacobson, — the two operations being done at tlie same time. There are many reasons for preferring this ])lan to that of leaving an inter- val between the two operations ; and almost the sole objection, — the difficulty of keeping the patient (juiet during the slightly longer time reqviired for the double operation, — may be obviated by the use of anassthetics. In this case, moreover, the operator has it in his power to decide, after section of the cornea, according to the indications he meets with, whether or not he will resort to iridectomy. LINEAR EXTRACTION. A very noteworthy improvement in operations for the congenital and traumatic forms of soft cataract consists in immediate removal of the lenticular sub- stance from the eye, through a small linear opening, instead of leaving the fragments of the lens to be slowly absorbed by the aqueous humor, as after the ordinary operation for division. The anterior capsule and the substance of the lens are freely divided by an extremely fine needle passed through the cornea, near its margin, the aqueous hu- mor not being evacuated. The minute puncture is then enlarged by a broad needle or the point of an iri- dectomy knife ; upon which some of the fragments of the lens are washed out with the flow of aqueous hu- REMOVAL OF SOFT CATARACT BY SUCTION. 89 mor, and the remainder may be removed with the curette or a small scoop. Should any portions remain they will be readily absorbed, provided the pupil is protected from pressure by having dilatation kept up by means of atropia. Operations by displacement of the pupil, or Iridde- sis, applicable to certain forms of congenital cataract, will be elsewhere described. REMOVAL OF SOFT CATARACT BY SUCTION. An ancient mode of extracting a lens of soft con- sistence by suction has recently been revived by Mr. Teale, and advocated' by him in the Royal London Ophthalmic Hospital Reports. I have obtained excel- lent results from his operation, performed with slight modifications. I use a broad needle for puncturing the cornea and make free division of the anterior cap- sule with the same instrument. A silver suction tube, of the size of the canula of a small exploring trocar, is connected by a short, flexible rubber tube with a glass bulb, and to this bulb is attached another longer tube which is held in the mouth of the operator. The silver tube is inserted through the wound made by the needle, and carried through the pupil, which has pre- viously been dilated by atropia, to the centre of the lens. Gentle aspirative efforts are now made, and tlie lenticular substance is drawn throuo-h the tube into the glass bulb. The mouth of the tube is slightly moved 90 RECENT ADVANCES IN OPHTHALMIC SCIENCE. from one point to another wltliin tlie capsule, so as to bring within its reach any fragments of the crystaHine which may be observed to remain. If the lens be quite soft, every portion of it may be drawn into the instrument, leaving the pupil clear. Should it have more tenacity, it may not be possible to remove tlie whole, and the fragments are left to dissolve, as after an ordinary operation for solution or a linear extrac- tion, or they might perhaps be removed, after having become softened by the aqueous humor, by a subse- quent suction operation. It is best to maintain dilata- tion of the pupil, as a precautionary measure, during the first days after the operation, and until we are sat- isfied that no danger is to be feared from pressure of unremoved flakes of lens against the iris. SUTURE OF THE CORNEA AFTER EXTRACTION OF CATARACT. So far as I know, the insertion of sutures in the cornea, after extraction of the lens, to facilitate pri- mary union of the flap, has never been performed or suggested, until lately by myself. I have done this in a considerable number of instances, and thus far with invariable success ; and after careful observation of the results obtained, can advocate this method as possess- ing numerous and important advantages. I prefer a straight needle, only a quarter of an inch long, made by cutting off the requisite length from the head of SUTURE OF THE CORNEA AFTER EXTRACTION. 91 the finest sewing needles and forming a new point. The needle is held and passed through the cornea by- means of a pair of firm forceps, and the suture, formed by a single strand of silk or the finest thread, is tied, not too tightly. This is allowed to remain until it cuts itself out, which is sometimes not for several days, or even weeks ; as there is danger of reopening the wound if its removal is attempted, unless during anaes- thesia. From the usual intolerance of the cornea of the presence of foreign bodies, we might expect that the suture would give rise to much irritation, but such has not been the fact, as I have known it to remain in situ seven weeks without causing inconvenience. Every one will appreciate the immense advantages to be gained by employing such a means of insuring immediate union of the corneal wound, — if the ques- tion of tolerance be once determined in its favor. Non-union of the edges of the flap is of itself one of the great dangers following the operation ; but we have thus placed it in conditions where its displace- ment will be prevented, its union by primary adhesion promoted, and swelling and suppuration of its border rendered most unlikely to occur. Prolapsus of the iris, another of the sequelas we have most to fear, is rendered almost impossible. By accomplishing a more speedy restoration of the anterior chamber and reten- tion of the aqueous humor, we escape or greatly les- sen the chances of inflammation of the iris, the crys- talline capsule, and the choroid. We are able to main- 92 RECENT ADVANCES IN OPHTHALMIC SCIENCE. tain dilatation of the pupil by the free use of atropia, without fearing that hernia iridis may be thereby in- duced, — and we thus obviate the dangers resulting from pressure of fragments of cortical lenticular sub- stance, or of capsule, against the pupillary margin of the iris. Lastly, we are able sooner to examine the eye with safety, and satisfy ourselves as to its condi- tion, and, if necessary, to institute measures to combat any threatening symptom in its incipient stage. IRIDECTOMY FOR RELIEF OF CLOSURE OF THE PUPIL. Whatever may be thought of the propriety of doing iridectomy, as a precautionary measure, to avert future attacks of iritis, in cases of partial synechia, — where the adhesions are limited and a large portion of the pnpil remains clear, — as has been proposed by some authors, — there can be no question of its propriety and necessity in instances where the aperture has become closed. Where complete obliteration of the j)upil has been established, the aqueous humor secre«"- ed in the postei'ior chamber, no longer passing freely into the anterior part of the globe, distends the iris and pushes it forward, till the vitality of its texture is destroyed, and it becomes a mere pouch, as it were, lying nearly or quite in contact with the cornea. IRIDECTOMY FOR RELIEF OF CLOSURE OF PUPIL. 93 At the same time pressure also takes place back- ward towards the important structures in the posterior part of the eye, and a slow process of disorganization is there set up, resulting, if interference be too long delayed, in utter extinction of vision. But if an artificial pupil be seasonablj' made, or the natural pupil re-established by corelysis, — thus re- opening communication between the two aqueous chambers, these morbid changes are arrested, and ex- cellent vision is oftentimes restored. In these instances, the surgeon should not refuse or delay to interfere because the patient has one sound eye, — as he can do, without detriment, in cases of cataract. To postpone relief is to sacrifice the eye ; and, apart from the possibility, the probability in fact, that a patient Avhose one eye has suffered from iritis may at some time have the other invaded by the same disease, or the chance that it might be destroyed by accident, it is too desirable to give him, if possible, the benefit of binocular vision, to allow of hesitation in doing an operation from which he incurs no risk, and is likely to have little inconvenience. As a rule, the loss of substance should, in these cases, be below the natural pupil, — that being the position admitting of most usefulness for an artificial pupil, — and it should fall short of rather than exceed the average dimen- sions of the natural aperture. 9-i RECENT ADVANCES IN OPHTHALMIC SCIENCE. IRIDDESIS IN CASES OF CLOSED PUPIL. Where tlie pnpil lias been for some time nearly or quite closed, and we judge from the aspect of the iris that its fibres have become so flaccid, and their con- tractile power so diminished, that the operation of corelysis, detaching the adhesions from the capsule of the lens, would be insufficient to secure a permanent opening, a small portion of the iris may be drawn out through a minute opening in the sclerotica, at the edge of the cornea, and an additional safeguard thus obtained for the patency of the pupil, while less de- formity is ])roduced, and the eye can better protect itself against a flood of light, than where iridectomy has been done. In nearly all these cases iriddesis should be downwards. IRIDDESIS IN CONGENITAL CATARACT. In some forms of congenital cataract there exists opacity of the central portion only of the lens, without the usual tendency to increase of the cloudiness to such an extent as to involve the whole crystalline. In these instances the patients see tolerably Avell in a moderate light, or after artificial mvdriasis. IRIDDESIS IN CONICAL CORNEA. 95 Great advantages may be gained, under these cir- cumstances, from displacing the pupil so as to bring it in apposition with a transparent portion of the lens, towards its margin, — while at the same time the op- posite portion of the iris is drawn over, so as to mask to some extent the central opacity. By proceeding thus, instead of operating for the removal of the lens itself, we retain for the eye the power of vision with- out cataract glasses, and of accommodation to different distances, — both of which functions would be abol- ished were the crystalline removed. Furthermore, this operation involves less risk than that of division of the lens, or than linear extraction or removal by suction. The unusual position and balloon-shape of the pu- pil creates a shght deformity on close inspection ; but this is of no importance compared with the advantage of being able to dispense with glasses, and attracts less attention than the wearino; of these. IRIDDESIS IN CONICAL CORNEA. The giving way of the centre of the cornea till it assumes a conical form is due to diminished resistance in the corneal tissue, not to excessive intra-ocular ])ressure. In fact, when the alteration of form has reached an extreme limit, and the apex of the cone 96 RECENT ADVANXES IN OPHTHAUnC SCIENCE. becins to be slightly cloudv, the tension of the globe is often rather lessened than increased. As the mor- bid change goes on, vision is confused, not merely by the increased m3'0pia, but by irregular refraction, and, later, by the central opacity ; until, in defiance of all ordinary remedial measures, useful vision is gradually lost, — a few cases only showing an arrest of the dis- ease after it has attained a moderate degree. In the course of trial of various optical expedients, it had been found that the infirmity was palliated and vision rendered more clear by looking through a nar- row slit, — and it occurred to ]\Ir. Bowman to apply to this affection the operation of iriddesis, devised by Mr. Critchett. The irregularity of refraction is thus diminished, by giving to the pupil an elongated form, and, in so doing, cutting off the disturbing lateral rays, — and a portion of the pupillary aperture is placed behind a ])art of the cornea which remains transparent and which is less changed than is the centre from its nor- mal curvature. A puncture should be made with a broad needle, through the sclerotica, at the extreme verge of the anterior chamber, — that the plane of the iris arid of the displaced pupil may continue normal, and not be inclined forwards, as would be the case were the wound made through the cornea. The edge of the pupil is then to be seized with a blunt hook or canula forceps and drawn out of the wound, where it is to be secured by ligature ; or the iris may be seized REMOVAL OF STAPHYLOMA OF THE CORNEA. 97 with the forceps nearer its ciliary margin, and simi- larly secured, — thus retaining in a measure the power of contraction of its circular fibres. The operation should generally be performed down- wards, and the shape of the pupil will be that of a balloon. A second operation, at the opposite point, was proposed by Mr. Bowman, — giving to the pupil a spindle-shape ; but the advantages of this are ques- tionable. As the conicity of the cornea has been thought to be lessened by the operation, it should be advused early in the disease, when this manifests a progressive tendency. REMOVAL OF STAPHYLOMA OF THE CORNEA. When the cornea has been almost entirely de- stroyed by pundent ophthalmia, its place is often sup- plied by a prominent cicatrice, formed of a peculiar tissue which seems to take the place of the cornea and iris, — to which the term staphyloma has been ap- plied. This cicatricial tissue has less resistance than the healthy cornea, and frequently gives way under the pressure from the intra-ocular fluids, bulging out- wards to such a degree that the patient may be unable to close the lids, or does so with difficulty. This pro- 5 G 98 EECENT ADVANCES IN OPHTHALJUC SCIENCE. trusion is often the source of pain and irritation, not only in the hds, but, from tension of the cihary nerves, in the eyeball itself. It is, moreover, liable to take on an inflammatory condition, in consequence of slight injuries or of exposure to cold, causing painful suppu- ration and entire collapse of the globe. To avoid these dangers and obviate the discomfort constantly occasioned by its presence beneath the lids, — as well as to remove the deformity which is a perpetual source of annoyance to the patient, — two operations have been proposed ; — enucleation of the entire globe, and excision of the staphyloma at its base. Removal of the globe subjects the patient to various inconveniences, which, though of no weight where the preservation of the other eye is in question, as in cases of sympathetic inflammation, are yet of importance in the circumstances we are now considering. If done, the deformity is considerable, and even though care may have been taken to leave the recti muscles and the cellular tissue of the orbit, as far as possible, in- tact, an artificial eye has not the amount of support requisite to its proper movements. Should no facti- tious eye be worn, the lids fall in and the eyelashes come into contact with the conjunctiva, keeping up a disajn'eeable amount of secretion from its irritated sur- face. In most cases, instead of resorting to this ex- treme measure, ablation of the staphyloma may be advantageously substituted. Mr. Critchett has proposed an excellent method of REMOVAL OF STAPHYLOMA OF THE CORNEA. 99 operating. The patient being etherized, four or five curved needles armed with sutures are passed through the globe from above downwards, just behind the ciliary region, thus including in front of them the whole of the staphyloma. These are thus placed to steady the globe and pre- vent the possible escape of the vitreous during the operation, and to allow of the sutures being tied im- mediately on the completion of the excision. The staphyloma is now excised with a sharp, narrow bis- tomy, the needles are drawn through, the sutures tied, and the edges of the wound thus brought to- gether. Speedy closure of the wound being desira- ble, it is well to have the silk or thread in each needle of a different color, that the sutures may be easily dis- tinguished from each other. The wound often closes by primary adhesion, or so much of it becomes united as to insure the healing; of the remainder by granulation, without loss of the con- tents of the globe. Simple water dressings are to be used. Recovery is rapid, and the stump obtained is not very unsightly, even if not covered by an artificial eye ; or, should one be worn, it affords a good support. In a few instances the attempt to preserve the ful- ness of the globe fails, inflammation coming on and causing suppuration of its contents ; but should this occur, little pain is usually felt, as the wound allows of the free escape of matter, and the resulting stump is nmch more comfortable to the patient, and gives bet- 100 RECENT ADVANCES IN OPHTHALMIC SCIENCE. ter support and moA'ement to an artificial eye, than when the globe has been removed. Where the staphylomatous tissue has considerable firmness, only an oval portion from its central part may be excised, with or Avithout previous insertion of needles, — the edges of the wound being brought to- gether by sutures. Nearly the natural dimensions of the globe may thus be preserved. DIPHTHERITIC INFLAMMATION OF THE CONJUNCTIVA. Though happily this disease is rare among us, and seems to be common only at Berlin and in Holland, whilst almost unknown in England and France, yet it does occur here, and may become more frequent. It prevails at the cold and damp seasons of the year, and oftenest affects children of from two to eight years of age, though adults may be attacked. Its invasion is rapid, a few hours sometimes sufficing to produce enormous tumefaction of the lids. They become hard and stiff, and can he everted with diffi- culty, owing to the infiltration of the conjunctiva and sub-mucous tissue witli a fibrinous exudation. Che- mosis exists beneath the conjunctiva of the globe, which shows here and there dots of extravasated blood. This chemosis is not serous, but is made up DIPHTHERITIC INFLAMMATION OF THE CONJUNCTIVA. 101 of the same fibrinous material which gives hardness to the lids, and its pressure upon the vessels interferes with the free circulation of blood. The secretions are at first dirty grayish and watery ; afterwards they are mixed with pus globules and fibri- nous fragments ; differing widely from the discharges in muco-purulent conjunctivitis. On everting the lids, thej^ are found lined with a firm, fibrinous mass, which is, perhaps, separated at its edges while still adhering firmly to the central portion of the lid. If detached with forceps or other- wise, slight hemorrhage follows. This false mem- brane is very rapidly reproduced, and may acquire a thickness of two or three lines in twenty-four hours. The principal danger arises from the liability to ex- tensive and intractable ulceration of the cornea, — produced by interruption of its nutrition and by tlie action of the acrid secretions. Very frequent use of slight astringents, with con- tinuous cold external applications, and cleansing the eye with mild fluids injected from a syringe, has proved more serviceable than active cauterization with nitrate of silver or other powerful remedies. Contraction of the conjunctiva and tarsal cartilage, and consequent entropion, is liable to ensue from the degeneration caused by this disease. A constitutional predisposition to this rare affection seems to exist in some families, and I have seen sev- eral children successively attacked on reaching a cer- tain asje. 102 RECENT ADVANCES IN OPHTHALMIC SCIENCE. REFRACTION AND ACCOMMODATION. Of all the advances which the last few years have witnessed in ophthalmic science, unquestionably the largest in its application is the development of the theories of accommodation and refraction, — which we owe, mainly, to the accurate observation and genius of Professor Bonders of Utrecht. THE FUNCTION OF ACCOMMODATION. A NORMAL eye, when in a state of rest, is adapted to receive upon its retina Avell-defined images of distant objects, — the rays emanating from which may be considered as parallel. It is then said to be accommo- dated for its far point, punctum remotissimum, desig- nated by the letter r. In practice, all objects placed at or beyond eighteen or twenty feet are regarded as. virtually at an infinite distance, — the rays derived from them diverging so little as to be in effect par- allel. But a normal eye is also capable of an unconscious adaptation, by which it can bring to a focus diverging rays, from an object situated very near it. It is then said to be accommodated for its near point, punctum proximum, designated by the letter p. THE FUNCTION OF ACCOMMODATION. 103 The distance between these two points is termed the range or latitude of accommodation, designated by A. This extends, generally, from three and a half inches, the near point of distinct vision, to an infinite distance. Anywhere within these limits, objects can be clearly seen ; beyond them, images of objects are no longer distinct, but circles of dispersion are formed upon the retina. Fig. 15. Diagram illustrating the physiology of accommodation in the emmetropic or normal eye. The upper half of this diagram rej^resents an emmetropic eye in a state of rest, the lower half in a state of full accommoda- tion for the near point A. The only difference in the refractive media is in the crystalline, which in the lower half of the figure is shown thicker and more sharply curved than in the upper half. In the upper half is shown a bundle of parallel rays which undergo successive refractions at the cornea and the two surfa- ces of the crystalline, so as finally to converge to a focus and thus form an image upon the retina N. In this condition of the eye divergent rays, as from the point A, and indicated by the upper dotted line, are not brought to a focus upon the retina, but tend to converge to a point farther back, as to A", thus forming 104 RECENT ADVANCES IN OPHTHALMIC SCIENCE. upon the retina N a vague circle of dispci-sion, instead of the clearly defined image which is essential to perfect vision. In the lower half of the diagram is shown a pencil of diver- gent rays, emanating from a near point, A. These divergent rays, having luidergone partial refraction in passing through the cornea, are again very strongly refracted by the sharply curved crystalline, so as finally to converge to a focus on the retina at N. Less divergent rays, or parallel rays, as indicated by the lower dotted line, are, under the same conditions, refracted so strongly as to converge to a point in front of the retina, as at A', a result wholly incompatible with distinct vision. The point A, repre- senting the nearest point of distinct vision, is called the near point, punctum proximum (})). It follows, therefore, that in a state of rest the emmetropic eye can see distant objects only, and the same eye in active accom- modation is fitted only for near vision. After many years of almost fruitless speculation upon the theory and mechanism of accommodation, it is now proved by positive mathematical demonstration that this most important function lias its seat in the crystalline lens, and that it is exercised by means of changes in the curvature of its anterior and in a slight degree also of its posterior surface ; which changes are effected, in a manner not yet fully explained, by the action of the ciliary muscle. For a long period the accommodative power was supposed by many to be exercised by elongation of the globe, and consequent increase of its refraction, by means of pressure exercised upon it by the recti mus- cles. This theory failed, however, to account for the total loss of accommodative power which is always THE FUNCTION OF ACCOMMODATION. 105 observed after removal of the crystalline lens in tlie various operations for cataract ; and it has been abso- lutely disproved by the occurrence of a case of total paralysis of all the motor muscles of the eye, but in which accommodation remained perfect. A second, and for a long time w^idely accepted the- ory, referred this power of adaptation to a change in the position of the crystalline lens ; but upon submit- ting it to rigorous mathematical analysis it was found that the requisite range of motion of the lens to ac- count for the varying conditions of accommodation would necessarily involve such a change in its position as could hardly escape the critical inspection of prac- tised observers. A third explanation assumed that there was no such thing as any active accommodative power, but sought to account for the observed phenomena by supposing that different parts of the refractive media, and par- ticularly of the lens, had the effect of bringhig the rays from external objects to a focus at different dis- tances ; thus considering the principal focus of the eye as a short line rather than a point, and assuming that all vision is the result of imperfectly defined retinal images. The true theory of accommodation was also long ago accepted as one of the ways in which distinct vis- ion is possible at different distances, and very strong if not conclusive arguments in its favor were adduced at the very beginning of this century by Thomas 5* 106 RECENT ADVANCES IX OPHTHALMIC SCIENCE. Young in a paper in the Philosophical Transactions ; but it was reserved for two observers of our own day, Kramer and Helmholz, working independently of each other and nearly simultaneously, to reduce the prob- lem to an ocular and mathematical demonstration. By the ingenious instruments devised by these eminent observers, the alterations of curvature in the crystal- line of an observed eye, as it is accommodated for near or distant objects, are made perfectly obvious to an observer, while it is at the same time evident that no change of curvature of the cornea takes place dur- ing the experiments. Fig. 16. Diagram explaining the change in position of the image formed by the anterior surface of the crystalline (after Donders). The observed eye is directed to the point A, and a candle and the eye of the observer placed symmetrically on either side of A, THE FUNCTION OF ACCOMMODATION. 107 as shown in the figure. Now the only rays from the candle which can reach the eye of the observer are those which are re- flected from the central portions of the cornea, and anterior and posterior surfaces of the lens. The rays reflected from tlie cor- nea will then reach the observer as if they came from the point a, and those from the posterior capsule as if they came from the direction c. The rays from the anterior surface of the lens, when the eye is at rest, as is shown by the flatter outline of the lens, will reach the observer's eye from the direction b. Im- ages of the flame, either real or virtual, Avill apjiear to the ob- server in the direction from which these rays respectively come, and will naturally be referred in position to the dark plane of the pupil, indicated by the line 1 1', upon which they may be repre- sented by the large white dots. If now the observed eye, still looking in the direction A, is strongly accommodated for some near object, the last-mentioned image will be seen to change its position so as to appear to be in the direction b'. This change in position can depend only upon a change in the place of the reflecting surface as indicated by the more convex dotted outline. The refraction of the rays from the two surfaces of the lens is not shown in the figure, as it occurs equally in the case of the incident as of the reflected rays, and therefore does not affect the demonstration. Figs. 17 and 18. Reflected images of a candle-flarae, as seen in the pupil of an eye at rest and in accommodation for near vision. Figure 1 7 represents the pupil of an eye in a state of rest, showing the three images, a b c, of the flame of a candle, formed 108 RECENT ADVANCES IN OPHTHALMIC SCIENCE. respectively by reflection from the cornea, anterior capsule, and posterior capsule. Figure 18 shows the same eye in a state of accommodation for near vision, — the pupil somewhat contracted, as indicated by the circular white line, and the image b, formed by the anterior capsule, changed both in size and in position. The smaller size of this image is the direct result of the in- creased curvature of the anterior surface of the crystalline, mak- ing it act as a convex mirror of less radius ; the change of posi- tion depends upon the protrusion forward of the same surface in consequence of the increased thickness of the lens in accommo- dation. The images a and c, formed respectively by the cornea and the posterior capsule, are not sensibly changed either in size or position ; proving that in accommodation there is no appreci- able change in the curvature of the cornea or in the curvature or position of the posterior surface of the crystalline. The mode in Avliich the action of the cihary muscle is brought to bear upon the lens, whether by drawing forward and relaxing the suspensory ligament, or in some other manner, is yet an undetermined question : that it is not the result of mai'ginal constriction of the lens by the iris, or ciliary processes, is proved by cases of congenital absence of the iris, in which the ciliary processes can be distinctly seen. An interesting case in the practice of Professor Von Graefe, in which the whole iris was accidentally torn away, shows also the same thing, the accommodation remaining unimpaired. Associated with this increase of thickness, and, there- fore, increased refractive power of the lens, during the effort of accommodation for near objects, we have cer- tain auxiliary changes in the iris. The most impor- THE FUNCTION OF ACCOMMODATION. 109 tant of these is the contraction of the pupil, by which the lateral rays, which require most refraction, are cut off, thus efficiently contributing to the formation of a clear image. The central part of the iris is also pushed forward and its peripheral portion backward ; but these changes seem to be a mechanical result of pressure, and probably only slightly modify percep- tion. Fig. 19. Diagram showing the relative condition of the eye when at rest and in strong accommodation (after Kramer and Ilelmholz, the anatomy after Arlt). The right-hand half of the diagram represents the eye in a statfe of rest, the left in full accommodation for near vision, the relative curvature of the crystalline on the two sides correspond- ing quite accurately in scale to the calculations of Kramer and Ilelmholz. The pupil is also shown as projected forward and somewhat contracted in accommodation. It will be noticed that the cihary processes do not, in either case, touch the margin of the lens, an observation due to Von Graefe, and confirmed by other investigators. Another coincident action occurs durins; the accora- 110 RECENT ADVANCES IN OPHTHALMIC SCIENCE. modative effort, — a convergence of the axes of the two eyes by consentaneous contraction of the internal recti muscles. In what manner the ciliary muscle be- comes reinforced by this external influence is not fully determined, but the fact is undoubted. It will thus be seen that the accommodative is quite another thing from the refractive power of the eye. Refraction is a passive condition, depending solely on the focal power of the transparent media ; so that the eye may be compared to an optical instrument, in which imao;es are formed in accordance Avith well- known laws of physics. No change can take ])lace in these images, except by an alteration in either the focal power or the position of the lenses. Accommodation, on the other hand, is a physiologi- cal action, the result of active muscular movements, which may be voluntary or "involuntary, by which the conditions of refraction are changed, — such an altera- tion taking place in the form of the crystalline lens that its focal power is increased. That such is the case is proved by the suspension of the adaptive func- tion Avhen paralysis of the ciliary muscle has occurred from disease, or has been artificially induced by the use of atropia, and by its total annihilation when the crystalline is displaced by accident or removed by oper- ation. Figure 20 represents the two halves of a myopic eye, the upper half in a state of rest, the lower half in full accommoda- tion for near vision. The refractive media are substantially the THE FUNCTION OF ACCOMMODATION. Ill Fig. 20. Diagram illustrating the action of the accommoJativc faculty iu the myopic eye. same as in the emmetropic eye, but the retina occupies a posi- tion farther back than normal, owing to the elongation of the eyeball. The relative position of the retina in the myopic as compared with the emmetropic eye is indicated by the elliptical outline N", the dotted curve N representing the normal condi- tion. In the upper half of the figure, which shows the eye at rest, parallel rays, indicated by the dotted line A, are brought to a focus at the normal distance of the retina N, but the actual retina N", lying as it does behind this point, is not in a position to receive the image. The result is, that the myopic eye, even when at perfect rest, cannot see distant objects clearly; the only rays, in fact, which can form a distinct image ujDon the retina N" are those which emanate from a comparatively near object, say at A", and which are sensibly divergent. This point A" represents, therefore, the extreme distance at which distinct vision is possible, and is called the far point, punctum remodssi- mum (r). In accommodation, as shown in the lower half of the figure, the increased curvature of the crystalline greatly augments the refractive power of the eye, so as to bring to a focus upon the retina N" rays emanating from the very near point P, punctum proximum (p), which is considerably nearer the eye than in the normal condition. 112 RECENT ADVANCES IN OPHTHALMIC SCIENCE. Fig. 21. Diagram illustrating the action of the accommodative faculty in the hyper- metropic eye. Figure 21 represents the two halves of a hypermetropic eye, the upper half in a state of rest, the lower in full accommoda- tion. The hypermetropic is shorter than the emmetropic eye, as is indicated by the flattened outline N', the dotted curve N rep- resenting the normal position of the retina. In the upper half of the figure, showing the eye at rest, the refractive power of the cornea and crystalline is just sufficient to bring parallel rays A to a focus at the normal distance of the retina N, but is not sufficient to form an image at the actual distance N'. The only rays, therefore, which can converge upon the retina of the hyper- metropic eye in a state of rest are convergent rays A" A', such as no natural object gives off. The exercise of the full accommodative power may be just sufficient to admit of the convergence upon the retina N' of par- allel rays A" A (in the lower half of the diagram), in which case distant vision is possible, but no power remains to be ex- erted in viewing near objects. Such a person has no effective power of accommodation. If, on the other hand, the hyperme- tropia is less in degree, there may still remain a surplus of accom- modative power sufficient to bring to a focus rays somewhat di- vergent ; in M-hicli case there will be a near point of distinct vis- ion, but farther from the eye than the near point of a normal eye. In very high degrees of hypermetropia the accommodative THE FUNCTION OF ACCOMMODATION. 113 power may be insufficient to form a clear image even with par- allel rays, in which case distinct vision is impossible at any dis- tance except by the aid of glasses. Fig. 22. Diagram illustrating aphakia (absence of the crystalline) and its effect upon vision in the emmetropic and in the myopic eye. Figure 22 represents an eye in which the crystalline is want- ing, either as the result of absorption or of removal by an operation for cataract. The refractive power which remains is too feeble to bring parallel rays A A to a focus at the retina N, but suffi- ces only to give them a convergent direction towards the point a, which is about three eighths of an inch behind the normal po- sition of the retina N. The feeble refractive power of the apha- kial, but otherwise normal eye, needs therefore to be strength- ened by the use of powerful convex glasses even for distant and still more for near vision ; if, however, the aphakial eye happens to be very strongly myopic, as indicated by the elongated outline a, the patient may enjoy perfectly clear vision for distant objects without the aid of glasses. The still more elongated outline a" shows the extraordinary degree of elongation of the globe which must be assumed to account for a very remarkable case, occur- ring under the care of the author, in which a patient after extrac- tion of cataract was able to read small type with ease at the dis- tance of twelve inches, and actually needed concave glasses for distinct vision at a distance. The course of the rays in this case is approximally indicated by the divergent dotted lines A" A". 114 RECENT ADVANCES IN OPHTHALMIC SCIENCE. RANGE OF ACCOMMODATION. The range or latitude of accommodative power may be determined by employing small frames across which fine wires are stretched, or plates in Avhich minute holes have been pierced, and measuring within what distances these are clearly defined. Or test types may be more conveniently used, and the nearest and farthest points noted at which they can be read with ease. Professor Donders has proposed that the range of adaptive power shall be expressed by ^, and its value in any particular case determined by the formula 1 1 1 A ~ P ~~ il ' If, therefore, we have a normal eye, able to see dis- tinctly from four inches (4"), its near point (p), to infinite distance ( cc ) its far point (r), we have A 4 «> 4 '^ V ■ Should the eye be myopic, having its far point (r) at eight inches (8"), and near point (p) at four inches (4"), we should find 1 1 _ 1 1 A 4 « ~ 8* The presbyopic eye, its far point (r) at infinite distance ( go ), and its near point (p ) at twelve inches (12"), has 1 _ 1 1 _ 1 A 12 =t 12* RANGE OF ACCOMMODATION. 115 The figures thus found represent the focus of an ideal lens which placed upon the crystalline would give to rays coming from the near point a direction as if coming from the far point. Another mode of determining the range of accom- modation, proposed by Professor Von Graefe, consists in placing a strong convex glass, say of six inches focus, before the eye, and noting the near and far point at which No. 1 of Jaeger's test types can be read. Held at six inches distance, (the principal focus of the glass,) the rays passing through it would be parallel on emerging, and therefore would strike the eye as if they came from infinite distance. The rays from the flu* point (r') and near point (p) thus found are refracted by the lens as if they came from the real far (r) and near (p) points. The mode in which the accommodation is found by the aid of the convex lens will be explained by the followins: diagram. Fig. 23. Diagram illustrating the use of a convex lens in determining the range of acciimmodation. Figure 2.3 represents the two halves of an emmetropic eye, the 116 RECENT ADVANCES IN OPHTHALMIC SCIENCE. upper half at rest as reqaiired for distant vision, the lower half accommodated for the near point A". By the interposition of a convex lens of about six inches focus, the divergent rays from a cer- tain point A", being the principal focus of the lens, (in the upper half of the diagram,) are converted into parallel rays so as to enter the eye as if they came from an infinite distance, as indi- cated by the dotted hue A ; the divergent rays from the point P (in the lower half of the diagram), being within the principal focus of the lens, are in like manner rendered less divergent, so as to enter the eye as if coming from the near point A", of the eye, as indicated by the dotted lines. The result is, that the eye thus armed with the lens has its far point (r) changed from an infinite distance to that of the princijial focus of the lens (i. e. six inches), while its near point is brought considerably within the principal focus. The whole region of accommodation is thus brought within the narrow limits of a few inches, and may, with a carefully constructed instrument, be very accurately measured. The range of accommodation is readily obtained by the follow- ingr formula : — 1 1 1 A~ P' ~R' A = 51 — F R'F P' being the distance from the near point P to theJens, and R' the distance of the far point A". The limit of the range of accommodation is reached when the object is brought so near that the rays be- come too divergent to be united on the retina by any change in the crystalhne. RANGE OF ACCOMMODATION. 117 Fig. 24. Instrument for measuring the range of accommodation. Figure 24 shows an instrument, altered from the ordinary shoemakers' measure, which is very useful for determinations of the range of accommodation by this method. The scale is marked in inches and fractions of an inch, and the stationary and sliding upright pieces are cut off to about an inch in length. The stationary piece is notched for the insertion of a lens of six inches radius, and the sliding one for a card on which ai'e letters No. 1. The instrument being supported against the malar bone, with the lens thus brought in front of the eye, it is easy to meas- ure at once and with accuracy the distances at and within which the patient can read the letters with facility. If we find that the far point is within the focal dis- tance of the lens we know that the eye has not a normal refraction, but is adapted, not for parallel, but for divergent rays ; — therefore myopic. On the contrary, if the far point is beyond six inches the eye can bring convergent rays to a focus upon the retina, — and is hypermetropic. These last conditions will be elsewhere considered. 118 RECENT ADVANCES IN OPHTHALMIC SCIENCE. ANOMALIES OF ACCOMMODATION. Among the pi-incipal disturbing causes affecting tlie adaptive power of the eye, we have three which de- serve special attention. One of these, presbyopia, is the effect of age, and sooner or later makes itself felt in most eyes as a limitation of the accommodation ; the others are, insufficiency of the internal recti muscles, and pa- ralysis of the ciliary muscle. PRESBYOPIA. Presbyopia, or old sight, was formerly supposed to be the opposite condition from m^ opia ; the former being regarded as a deficient, as the latter is an aug- mented refractive power. It is now known that this opinion was erroneous, the refractive power for distant objects remaining undiminished in presbyopia ; par- allel rays being still brought to a focus upon the retina. The actual change consists in the recession of the near point from the eye, and a consequent limitation of the range of accommodation. Hence, although still able to read No. 20 of Jaeger or Snellen at twent}^ feet, there is difficulty in seeing small objects ; as, if close to the eye, the rays are too divergent to be united upon the retina, and if" placed at the distance from the PRESBYOPIA. 119 eye to which the near point has receded, the images formed upon the retina are too small to be distinctly- perceived. This recession of the near point is occa- sioned by an increase of hardness in the crystalline lens, so that its form can no longer be readily changed and its convexity increased by action of the ciliary muscle. The researches of Professor Bonders and others have proved that this change in the crystalline begins very early (in emmetropic or normal as well as in ame- tropic eyes), — even at ten years of age, — and goes on, gradually lessening, with advancing life, the ability to accommotlate. At about the age of forty, the near point is at eight inches from the eye, and it is now agreed to consider this distance as the point of com- mencement of presbyopia. In advanced life the far point may also recede, probably because the denser crystalline loses not only its susceptibility to a change of curvature but also a portion of its refractive power. The eye thus becomes not only presbyopic by limited accommodation, but hypermetropic by lessened refrac- tion. Glasses, of lower power than those used for reading, are then required for distant view. Presbyopia may be distinguished from amblyopia, or weak sight, by testing the visual power with convex glasses. A merely presbyopic eye ought, if provided with suitable glasses, to see No. 1 of the test types as well as ever, at from eight to twelve inches distance ; while an eye in which the acuteness of vision is di- 120 RECENT ADVANCES IN OPHTHALMIC SCIENCE. minished, cannot see very small type at any distance, with or without jrlasses. As presbyopia is due to alterations of consistence in the crystalline lens, rendering its form less susceptible of modifications by accommodative effort, it follows, that myopic and hypermetropic, as well as normal eyes, are subject to this change. In myopic persons the range of accommodation is thus greatly limited. It is a mistake to suppose, as is often done, that short- sightedness grows less witli age, except that the change in the refractive power of the lens incident to old age may in some cases suffice to correct moderate degrees of myopia ; as, though a myope is able, and in fact compelled to place small objects further from his eyes than formerly in order to see them well, yet as his far point remains the same, or nearly so, he is by no means the gainer by this shortening of the range of adaptation, — wliich has removed his near point from three to twelve inches, wliile his far point continues at, for instance, eighteen inches. Presbyopia, as we have defined it, cannot, however, occur in extreme myopia, where the far point is al- ready Avitliin eight inches. In cases where pi'esbyopia supervenes upon hypermetropia we have even more serious disturbance of vision, for loss of accommodation is added to already deficient refraction. Practicall}', we may regard presbyopia as beginning when a person finds himself compelled to place small objects at an increased distance from his eyes, and to PRESBYOPIA. 121 seek a brighter light, which not only illuminates the objects on which it is thrown, but, by inducing con- traction of the pupil, admits fewer lateral pencils of light, and thus lessens the circles of dispersion. This change generally takes place at about forty-five years of age, in eyes originally normal. When these symptoms of loss of adaptive power begin to be felt, the eyes should be aided by convex glasses of sufficient power to compensate for the defi- ciency ; otherwise they are fatigued by futile efforts, and yet more serious disability may result. It is useless to postpone wearing glasses, in the hope that the necessity for resorting to them may be overcome. In the upper half of Figure 15 we have an iUustration of tlie condition which exists in presbyopia. Parallel rays arc brought to a focus upon the retina ; but the crystalline, having lost its sus- ceptibility to change of form, can no longer accommodate itself for divergent rays coming from the near point A. The increased refraction necessary to bring these I'ays to a focus at N (instead of at A", where they would naturally unite) must therefore be obtained by placing a suitable convex glass before the eye, the clfect of which on rays from the near point will be equivalent to that exercised by the crystalline in a state of full accommoda- tion, as shown in the lower half of the figure. Such a glass should be selected as will brins; the near point to a distance dependent upon the particular recptirements of the patient, say eight inches or rather more, for reading, sewing, «S:c. If, following Professor Bonders, we accept 8" as the 6 122 RFXENT ADVANCES IN OPHTHALMIC SCIENCE. Starting-point of presbyopia, its degree may be simply expressed in symbols by the difference between the assumed normal power of the eye Avhen accommo- dated for near objects (i. e. ^) and the observed power of the presbyopic eye, which avc may express by - . We have, then, the formula p,=i-i. 8 n Now, if by testing an eye with small type we find its near point at twelve inches, we have n =: 12 or - = — . The value of Pr then will be n 12 8 12 24 which simply means that a convex glass of 24" focal length will be required to neutralize the presbyopia and enable the patient to see with distinctness a small object placed at the distance of 8" from his eye. We must generally, however, give rather weaker glasses than those thus calculated, as the convergence of the optic axes at a shorter distance will otherwise bring the near point within less than eight inches. The weakest glass which gives distinct vision at the desired distance should be selected, especially if the range of accommodation is not extensive. A myopic person may, as he grows older, become also presbyopic, — and Avhile still needing concave glasses for a distance, to lessen his excessive refrac- tion, may nevertheless require convex glasses for small objects, to obviate his loss of accommodation. PRESBYOPIA. 123 When presbyopia supervenes on hypermetropia, it gives rise to more disturbance than when it occurs in a normal or a myopic eye. In hypermetropia all vis- ion, even for remote objects, requires an effort of adap- tation, which must be yet more increased if the eye be directed to near and minute objects. When, there- fore, the crystalline begins to yield less and less read- ily to the accommodative effort, vision becomes more and more difficult at first for near, and afterwards for distant objects. We have here, therefore, to supply two convex glasses, one for distant vision, to compen- °sate for the want of refraction depending on hyperme- tropia, the other for reading, &c., to supply both the deficient refractive power and the loss of accommo- dation. The usual formula for ascertainincr the rano;e of accommodation may also be applied in presbyopia. \A P R/ If the near point be at twelve inches, the far point at infinite distance, we have 1 1 1 1 A 12 <» 12 ' Rapidly increasing presbyopia, especially if the pa- tient is in poor health or has been under depressing influences, is to be regarded with suspicion, — as it is not an unfrequent precursor of glaucoma. If there- fore a j^atient has been obliged within a short period 124 RECENT ADVANCES IN OPHTHALMIC SCIENCE. repeatedly to augment the strength of glasses, inquhy should be made if any other symptoms have been ob- served, such as iridescent colors around the lamp, occa- sional loss of sight for a short J;ime, or pain in or about the eye, — and we should examine if there be any increase of tension of the globe or evidence of com- mencing change in the optic disc. INSUFFICIENCY OF THE INTERNAL RECTI. It is not uncommon to hear complaints, especiall}' from myopic patients, of inability to use the eyes con- tinuously, though they exhibit no serious changes when viewed with the ophthalmoscope, have good latitude of accommodation, and perfect acuteness of vision. If one eye is screened whilst the other looks directly forward we observe that the covered eye deviates out- ward, though it instantly assumes a position in har- mony with its fellow when the screen is removed. If a small object, a pencil for instance, is brought gradu- ally very near the eyes, they at first converge nor- mally towards it, but suddenly one or both eyes turii outward, as if Avearied, — denoting insufficient j)ower in one or both recti interni. We can readily suppose that fatigue must here follow prolonged efforts to keep up the degree of convergence necessary for reading or other work requiring minute attention. The power INSUFFICIENCY OF THE INTERNAL RECTI. 125 of converging the axes of the two eyes upon any near object is intimately connected, although in a manner not yet fully understood, with the function of accom- modation, so that any considerable disability of the in- ternal recti is in general associated with more or less disturbance of the accommodative faculty, giving rise frequently to asthenopia or fatigue of sight. If the patient employ his eyes very much upon small objects, a confirmed divergent squint is pro- duced. To avoid double vision, which necessarily occurs M'hen exhaustion of the internal recti puts an end to the proper convergence of the eyes, the eye most deficient in power turns yet more outward, and gives up all attempt to share in the visual act, — neg- lecting altogether the image formed on a part of its retina which does not correspond with the place of formation of the image in the stronger eye. Insufficiency of these muscles may be sometimes relieved by persevering and careful exercise with prisms, to overcome which, and avoid the formation of double images, the muscles are forced to increased exertion. But in most cases division of the external rectus affords the most speedy and effectual means of cure, — though it is generally necessary, and almost always where the myopia is considerable, to advise also the use of concave glasses in order to obtain the full benefit which should result. 126 RECENT ADVAN'CES IN OPHTHALMIC SCIENCE. PARALYSIS OF THE CILIARY MUSCLE. Loss of power in the ciliary muscle is not an infre- quent consequence of diphtheria, and may also follow other exhausting diseases, — or it may occur in syphi- litic or chlorotic conditions of the system, — or as a result of cerebral disorder. The ciliary branch of the third pair may be alone paralyzed, or the branches supplying the iris and those distributed to the external muscles of the globe may be simultaneously affected. In the former case the contractility of the pupil and the various movements of the eyeball remain unimpaired ; the higher degrees of the affection are marked by mydriasis and diver- gent strabismus. The effect of ciliary paralysis upon vision varies greatly, according to the refractive condition of the eye. Consisting, as it does, in a loss of accommoda- tive power, it will be most felt by those patients who depend most upon that power in the ordinary use of the eyes. It follows, therefore, that a strongly hyper- metropic person who exercises his accommodative fac- ulty in every act of vision, even of the most distant objects, will altogether lose the power of seeing any object with distinctness ; an emmetropic eye, on the other hand, loses only the power of seeing near ob- jects clearly, but remains unimpaired for 'distant vision ; PARALYSIS OF THE CILIARY MUSCLE. 127 while a myopic eye, which without the exercise of accommodation sees distinctly at the distance of a few feet, becomes aware of the loss only when looking at very near objects. An artificial paralysis may be temporarily produced by the use of solutions of atropia of four grains to an ounce of water. A weaker solution suffices to dilate the pupil, but does not wholly suspend the action of the ciliary muscle. General tonic treatment is in these cases of the first importance. At the same time, repose from accommodative efforts is to be obtained by giving the patient such convex glasses as will allow him to see distinctly with- out exertion. As the system regains its normal condition and the power of the ciliary muscles is gradually restored, the strength of the glasses may be diminished, and they may be used less and less, and finally altogether dis- pensed with. The extract of Calabar bean, applied to the eye, has been of great use in some cases of this affection, and gives promise of rendering excellent service as a means of treatment. 128 RECENT ADVANCES IN OPHTHALMIC SCIENCE. SPASM OF THE CILIARY MUSCLE. In this rare affection tlie crystalline appears to be continually acted upon, and a state of excessive but varying convexity of its surface is kept up, so as greatly to interfere with, or even Avholly to prevent, the voluntary exercise of the accommodative function. Distant objects are therefore seen very indistinctly ; and altliough those near the eye are seen clearly for a short time, the effort of close attention soon fatigues. This morbid condition is oftenest met with in per- sons who use the eyes continuously for fine work. It sometimes comes on suddenly. Temporary spasmodic action is occasionally induced where the extract of Calabar bean has been employed as a local remedy. In combination with such tx'catment as may be indi- cated for lessening nervous sensibility and improving the general health, we should enjoin rest from fatigu- ing employment of the e3'es ; — and even, if necessary, place the accommodative power in i*epose by paralyzing the ciliary muscle by means of a solution of atropia. The use of convex glasses may often be advised for a time, in order to insure complete rest from accommo- dative efforts. ANOMALIES OF REFRACTION. 129 ANOMALIES OF REFRACTION. An emmetropic or optically normal eye has, in a state of rest, a refractive power capable of concentrat- ing parallel rays to form a distinct image upon the retina, — and furtlicrmore, possesses the faculty of in- creasing this refraction, by the exercise of accommo- dation, to a degree which admits of the formation of a well-defined image from even strongly divergent rays. But there are eyes which have not normal powers in a state of rest, and in which no change in the cur- vature of the crystalline lens which is within the ca- pacity of the ciliary muscle to effect is sufficient for perfect accommodation. Such abnormal eyes owe their defect to one of three conditions, generally inhe- rent in the construction of the globe ; — the optic axis is either too long, giving excessive refractive power, and constituting myopia ; or it is too short, causing in- sufficient refraction, or hypermetropia ; or the sur- faces of the cornea or lens may present an unequal curvature in different meridians, creating irregular refraction, or astigmatism. Figure 25 represents sections of three different eyes, the outer or elongated elliptical outline being that of a myopic eye, the mid- dle or circular outline being that of the emmetropic or normal eye, and tiie inner or flattened elliptical outline beiilg fliat of a hypermetropic eye. They are all represented as in a state of 6* I 130 RECENT ADVANCES IN OPHTHALMIC SCIENCE. Fig. 25. Diagram showing the relative form of the myopic, emmetropic, and hypermetropic eye. rest, that is, without the exercise of any accommodative power. The myopic eye, from its long antero-posterior diameter, is capa- ble of converging upon its retina at N", divergent rays emanating from a point A", which is its far point for distinct vision ; the emmetropic eye, under the same conditions, can only })ring to a focus upon its retina at N parallel rays A A, or those which emanate from very distant objects ; while the hypermetropic eye, Avith its antero-posterior axis abnormally short, has such a defi- ciency of refractive power that it can only bring to a focus upon its retina at N' rays already convergent as A' A'. Each of these three kinds of rays is shown by a particular style of engraved line ; and it will be observed that while each set comes to a focus, and so forms an image at the retina of the eye for which it is adapted, the others are received either before or after reaching their respective points of convergence, and so form either mere circles of diffused light, or at best but very vague and confused pictures of external objects. This figure also explains the reason for the diminished acute- ness of vision often existing in myopic eyes. Inasmuch as the retina, which in a normal eye would occupy the space shown by the line H N H, has become distended over the larger surface II N" II, its nervous elements, being thus diffused, are capable of receiving a less vivid impression of an image formed upon any given superficies. MYOPIA. 131 MYOPIA. Various causes were formerly assigned for short sight, — too great convexity of the cornea or of the crystalUne, a misplacement of the latter, etc. Recent observations have proved that it depends, not upon these supposed causes, but upon an elongation of the antero-posterior diameter of the eyeball, involving a faulty position of the retina with reference to the cornea and crystalline. The rasult of this abnormal conformation is, that the retina lies behind the principal focus of the eye, so that parallel rays coming from dis- tant objects are received upon that membrane in the form, not of a distinct image, but of more or less vague circles of dispersion. Divergent rays, on the other hand, coming from near objects, may converge to a focus upon the misplaced retina, and thus afford dis- tinct vision without any exercise of the accommodative faculty. Vision is therefore perfect for near objects, but more or less defective for distant ones. See Fig. 25. Measurements by Professor Donders and others have shown a leno-th of from one and one fifth to one and two fifths inches in some myopic eyes ; whilst others, in which hypermetropia, the opposite refractive condition, existed, had an antero-posterior diameter of less than four fifths of an inch. See Fig. 25. But 132 RECENT AD\^\^'CES IN OrHTHALMIC SCIENCE. we do not require an autopsy to satisfy ourseh'es of the fact of this elongation. The unusual length of the globe may be seen, at the outer canthus, by separating the lids and directing the patient to look as far as pos- sible towards the opposite side. The eyeball is then observed to fill, more than commonly, the space at the outer angle, and to have evidently an oval, acorn shape, instead of a nearly spherical form. Myopia results then, in most cases, from anatomical conformation ; it is often hereditary ; and, except in the slighter cases, is capable of being scarcely if at all modified for the better by age or by treatment. On the contrary, there is a strongly progressive tendency in cases where this affection exists in a high degree, — and even where it is slight in amount there is gener- ally a period of temporary increase. This tendency may be greatly enhanced by improper management, or on the other hand may be in a measure counteracted by using suitable precautions. There can be no doubt that myopia exists from birth in numerous instances, though its presence is unsuspected until the child is old enough to observe and to study. On reaching the age of about fifteen, — that is to say, soon after the time when, having learned how to study, he applies himself more closely to his books, or when perhaps he begins an appren- ticeship to some trade requiring close attention to minute objects, — the myopia, hitherto only moderate in degree, becomes much increased. This change results MYOPIA. 133 from pressure of the recti muscles upon the globe dur- ing the act of convergence ; which tends to cause yet more extension of its long diameter. Where the elon- gation of the globe is inconsiderable, the myopia, after reaching a certain point, continues stationary. Where, on the contrary, the tunics of the globe are already abnormally thinned, and have assumed an egg-shape, the action of the muscles, together with the conges- tion of the ocular vessels occasioned by leaning the head forward in readino; or workino;, tends to increase the malformation of the globe, and favors the produc- tion of posterior staphyloma, or enlarges it if pre- existent. Such a yielding of the posterior part of the globe increases yet more the myopia, requiring addi- tional efforts to overcome the altered conditions of re- fraction ; — the staphyloma and myopia thus act and react upon each other- to mutual disadvantage. It is rare that staphyloma is absent in high degrees of myopia, and it is not unfrcquent where this is but moderate in amount. It is the demonstration of these facts, proving that myopia is often to be looked upon as a disease and not merely an infirmity, which has given so much in- terest and importance to modern researches upon the subject. In myopic eyes we have, then, two special abnor- mal conditions, — elongation of the globe, which places the optical centre farther from the retina; and dis- tension of the tunics, which dilutes, as we may say, 134 RECENT ADVANCES IN OPHTHALMIC SCIENCE. the perceptive power, by extending the nervous ele- ments of the retina over a larger space than that nat- urally occupied. See Figs. 25 and 26. This expansion of the nervous elements over a larger space than normal (see Figs. 25 and 2G) will explain the fact, that even with the best adapted con- cave glasses the vision of many myopes is still very imperfect for distant objects ; for it must be remem- bered that concave glasses, while they increase the distinctness of the retinal image by bringing parallel rays to a focus at the proper place, may nevertheless so far diminish its size, by displacing the optical centre of the eye, as in part or wholly to nevitralize the ad- vantage gained by clearer definition. Myopic persons have, in fact, very often a certain degree of ambly- opia. Near sight is most common amono; the better edu- cated classes of society ; and, in the laboring class, is more frequent among the artisans of cities than the agricultural population. The reason is obvious ; an hereditary predisposition may exist in an equal num- ber of both classes ; but it is far more likely to be de- veloped in those -whose attention is mostly directed to minute objects observed at short distances from the eyes, and with the head bent forward so as to favor congestion of those organs, than in those who scarcely use the eyes for other than large and distant objects. In the latter class the influence of heredi- tary predis|X)sition may remain inoperative. MYOPIA. 135 A moderate amount of stationary myopia is scarcely a defect, and involves no future dangers ; but where the affection is considerable and progressive it consti- tutes a positive disease, the course of which should be watched and its advance prevented, lest, if unchecked, it terminate in separation of the retina, disorganization of the choroid and vitreous, and deteriorated or ru- ined vision. The frequency of posterior staphyloma should lead us to assure ourselves, by means of the ophthalmoscope, as to its presence or absence, and whether, if present, it be complicated with inflamma- tory symptoms. Should such be discovered, it will be important to avoid all employment which might in- duce congestion of the eyes and thus increase the staphyloma, and, if necessary, we should advise anti- phlogistic or other treatment. Blue glasses are often highly serviceable under these circumstances, as by neutralizing those rays of the spectrum which are the most irritating, they favor the subsidence of ocular congestion. It is evidently useless for persons affected with my- opia to deprive themselves of the very great aid to be derived from the proper use of glasses, in the hope that with advancing years their vision may become normal. Something, it is true, may be gained by long-con- tinued traininj:, and a slio;ht change results as ao;e ad- s' o o o vances, from a diminution in the refractive power of the crystalline (hypermetropia acquisita). But, ex- 136 RECENT ADVANCES IN OPHTHALMIC SCIENCE. oept in very slight cases, the gain thus eventually obtained is insignificant, and in the mean time the sacrifice in enjoying no really distinct perception of distant objects is very great. Fig. 26. Myopia corrected by the use of a concave lens. Figure 26 represents a myopic eye at rest, in which condition the divergent rays from its far point A" are refracted to a focus upon its retina N". Parallel rays A A being, under the same conditions, refracted to a focus at the normal position of the re- tina N. By the interposition of the concave lens L the parallel rays A A are rendered divergent so as to enter the eye in the same direction as if emanating directly from A", and are thus made to converge to a focus upon the actual retina X". The degree of myopia in any particular case is measured by the far point (r) for distinct vision, and is expressed by the letter JNI. It may be very easily and exactly determined by means of Jaeger's, or still better Snellen's test letters, or those appended to this volume. A person with good vision will distinguish the different sizes of letters at the appropriate distan- ces with about equal facility. A myope, on the other hand, will distinguish the smaller letters held near the MYOPIA. 137 eye while he will fail to read the larger letters at a greater distance. If now a myope reads Nos. 1, 2, 3, and 5, at the distances respectively of 1, 2, 3, and 5 feet, but fails to distinguish Nos. 8, 10, 12, and 20, at 8, 10, 12, and 20 feet, we decide that his myopia is of very low degree, and represent it by a fraction having for its numerator unity, and for its denominator the immber of inches at which the corresponding size of type is clearly read, that is, No. 5 being read at the distance of 5 feet, or 60", we have tiO' which means that the excessive refractive power of the eye is equal to a convex lens of sixty inches focal length, and tliat to neutralize it will require a concave lens of the same negative focus. If now, to take another example, we find that the patient sees No. 2 clearly at two feet or 24 inches, but caimot distinguish No. 3 at three feet, or the laro^er sizes at corresponding distances, we say that in his case M=i-, and will require a negative or concave glass of 24 inches focus. This test, although a convenient one, is subject to many sources of error, and the results obtained by it should therefore be taken as approximations only to the real degree of M. It serves, however, to suggest 138 RECENT ADVANCES IN OPHTHALJUC SCIENCE. to US a suitable glass with which to try the patient, and we can then easily correct it in the following manner : — Suppose that in the second case which we have just instanced, we try the patient Avith a pair of 24-inch con- cave glasses, and direct him to look at a distant object, say No. 20 of the test types, at 20 feet distance, — he will probably at once perceive a very great improve- ment ; if now we place in front of his glasses a second very weak pair, say No. 60 concave, and if with this addition vision is further improved, the glass we are testing is too weak ; if with it vision is not more dis- tinct, but on the contrary is made better with convex 60, the glass is too strong. If not improved by adding either a weak concave or convex glass, the one first selected is the best the patient can have. Should the addition of the second pair of weak glasses result in greater distinctness of vision for dis- tant objects, the correction may be applied by the fol- lowing formula: — x~ a^ b' h±a ab that is, the focal distance of the corrected glass (a:) is equal to the sum or the diiference of the focal lengths of the two glasses divided by their product. Should a myope desire glasses for reading as well as for viewing distant objects, he may often, with advan- MYOPIA. 139 tage, use a pair of less power tlian those he requires for far sight. Should his far point be at 6 inches, and he wishes to read at 12", the requisite glass wouid be indicated by the formula, — - -j- — = -. If he lias good power of accommodation, and his eyes do not exhibit posterior staphyloma, he may be even allowed to wear glasses for reading which are sufficiently strong to completely neutralize his myopia. But should he have limited power of adaptation, and at the same time amblyopia arising from distention of the fundus of the globe, it will scarcely be prudent to per- mit the use of any glasses for near vision. It is important to ascertain the amount of accommo- dation in myopic eyes, to aid us in deciding whether or not glasses should be allowed for near objects. Pro- fessor Donders determines this by first giving such glasses as render distant objects most distinct. The patient is then directed to read No. 1 of the test types, and the distance of the near and the far point, which gives the latitude of accommodation, is noted. The accommodation may also be measured without concave glasses, by observing the distance at which No. 1 can be read. If, for instance, the far point (r) is at 6, and the near point (p) at 3 inches, we have A = ; that is, A - ' - 1 - i ^ — 3 6 — 6 But the convergence of the optic axes at short dis- tances renders this method less positive in its results than that previously given. 140 RECENT ADVANCES IN OPHTHALMIC SCIENCE. Glasses worn for distant vision should be of the least power Avhich will afford sufficient distinctness ; as the eyes are directed only a small part of the time to far distances, but more frequently to objects Avhich are comparatively near. Should the glasses have too high power, they will be too strong for looking at these nearer objects, and will require efforts of accommoda- tion, — from which the eye should be spared as much as possible. Glasses of the same focal power should generally be used for both eyes, even where they have different degrees of myopia ; as less confusion is pi'actically found to result than where we attempt to adapt a glass to each eye. The glass chosen should in most cases be that which suits the least myopic eye. When intended for distant vision the centre of the glass should be in front of the centre of the cornea. Otherwise the eye looks through the edge of the lens, and the effect is more or less that of a prism. But if designed for reading, the lenses may be a little less separated from each other, and thus adapted for the convergent position of the optic axes. We owe to Professor Donders the demonstration of an interesting fact in relation to myopia, — that it is the most frequent cause of divergent strabismus. The phenomena arising from this s^ffiliation will be explained Avhen speaking of the last-named affec- tion. HYPERiMETROPIA. 141 HYPERMETROPIA. It is only within a few years that this affection, the opposite of myopia, can be said to have been fully rec- ognized in its true character. Many cases occurred, it is true, troublesome to physician and patient, in which no obvious symptoms existed, and where vision was perfectly good ; but where the eyes were incapa- ble of continued use, especially upon small objects, Avithout experiencing so much fatigue as to compel suspension of their employment. The researches of Professor Donders have shown, that in a large proportion of these cases the cause of the inability is to be found in hypermetropia, or defi- cient refractive power. This condition, like myopia, generally depends on defect of construction of the globe ; the antero-poste- rior diameter being too short, so that parallel rays are brought to a focus at a point behind the retina. See Fig. 25. As, therefore, only convergent rays can be concen- trated to a distinct retinal image when the eye is at rest, and even parallel rays from remote objects require an effort of accommodation, we can understand the pain and fatigue resulting from long-continued use for near objects, from which divergent rays only are re- ceived. At first, however, these objects are seen 142 RECEXT ADVANCES IN OPHTHALMIC SCIENCE. clearly, for the eye is capable, ^^ro tempore^ of the requisite accommodative effort ; but this strain of the ciliary muscle cannot be long kept up without produ- cing a sensation of lassitude and discomfort, -which presently extends from the eye to the brow, is fol- lowed perhaps by a loss of clearness of perception, and at length compels a cessation of the occupation which requires such tension. The eyes being left for a while in repose recover their adaptive power, and can be again used for a time, to become again disabled by a recurrence of the symptoms after a longer or shorter period. Fig. 27. Hypermetropia corfecteil by the use of a convex lens. Figure 27 represents a hypermetropic eye at rest, in which <'ondition the convergent rays A' A' are refracted to a focus upon its retina N'. Parallel rays A A being, under the same condi- tions, refracted to a focus at the normal position of the retina X. By the interposition of the convex lens L, the parallel rays A A are rendered convei^ent, and thus enter the eye in such a con- dition as permits the formation of a distinct image upon the ac- tual retina N'. As in myopia, a peculiar form of the eyeball may HYPERMETROPIA. 143 be observed on inspection. The patient being told to look strongly inwards, we find at the outer canthus an evident shortness of the globe from before backward. It does not fill the space at the outer angle like a my- opic, or even a normal eye, but its posterior surface shows a rapidly retreating curve. Its antero-posterior diameter has perhaps only four fifths of the length of the normal standard. In extreme cases the globe has the shape, as contrasted with a myopic eye, that a turnip has compared with an egg. At a given distance the image of any object will be smaller in a hypermetropic than in a normal eye ; as, from the shortness of the axis, the optic centre will be nearer the retina. The near point of distinct vision will of course be farther from the eye. Hypermetropia involves no such progression and tendency to deterioration of structure and function as we too often find in myopia, where, as we have seen, there is frequently a disposition to staphyloma of the sclerotica, atrophy of the choroid, and distention or even separation of the retina. It is a permanent con- dition ; modified, however, in advancing age, by su- [)ervening presbyopia, — the symptoms arising from the original conformation beintj thus increased. It is found that the actual degree of hypermetropia cannot always be estimated by tests with glasses, as the amount of myopia may be ; and that it is fre- quently necessary to add to the manifest a certain amount of latent hypermetropia, in order to have the 144 RECENT ADVANCES IN OPHTHALMIC SCIENCE. sum of the ahsnlute affection. The reason of this can be explained in few words. A person having a normal eye sees large objects at a distance perfectly well, without making use of any accommodative power, — which he reserves for smaller and nearer objects. But if hypermetropic, he does not see even distant objects clearly, when the eye is passive, but is compelled to bring into use a portion of liis accommodation. This he may do unconsciously, and in so doing may mask and render latent a part of liis hypermetropia. Thus, though having no apparent hypermetropia, he has less accommodative power in reserve for the perception of minute objects, and soon experiences symptoms of asthenopia or fatigue of the eyes, if he employ them a long time continuously upon such objects. Especially is this true where, as is often the case, a hie^h degree of hypermetropia is associated with a limited range of accommodation, and Avhere the effort necessarv for the formation of distinct iman;es would be, perhaps, twice what would be requisite in a normal eye. To ascertain the amount of absolute hypermetropia, and determine how mucli has been rendei'^d latent by exertion of the accommodative power, it is necessary to paralyze the ciliary muscle by atropia. A drop or two of a solution of four grains of the sul})hate in an ounce of water is applied to the eye, and requires some two hours for its complete effect. Only one eye at a time should be subjected to its HYPERMETROPIA. 145 action, that too much inconvenience may not be felt ; as until its effects have subsided it is difficult to see small objects. If we then place the patient at a distance of twenty- feet, we find that to read No. 20 of Snellen's or of our test-types, — which a normal eye can do even after mydriasis and paralysis of accommodation, — he requires the assistance of a convex lens ; or if pre- viously needing glasses for viewing distant objects, he now requires a much stronger one than before the sus- pension of his accommodative power. The glass whicli is now required for distinct vision at a distance is the measure of the absolute hyperme- tropia, which we may express thus, ^=12' ^' '^"- If, without having paralyzed the ciliary muscle, we o-ive a patient such a glass as seems to be sufficient for liim, he may find his symptoms only partially relieved. We have, in foct, only taken account of the apparent, and have ignored, what is perhaps even larger in amount, the latent hypermetropia. On the other hand, if we at once give glasses strong enough to neutralize the absolute hypermetropia, we perhaps only increase the patient's discomfort, for as he cannot immediately lay aside his habit of constantly emi)loying a considerable amount of accommodation, we give him an excess of refractive power, and virtu- ally render him myopic. He may, therefore, be al- 146 RECENT ADVANCES IN OPHTHALMIC SCIENCE. lowed weaker glasses at first, — sometimes of even less power than suited him previous to the use of atro- pia, — their strength being afterwards increased, as his habit of continuous accommodation is gradually laid aside, till he reaches the power which is equivalent to the amount of his hypermetropia. Theoretically, it is for the advantage of the hyper- metrope to wear his glasses constantly, even for dis- tant sio;ht, — as he thus avoids taskino; his accommoda- tive power for such purposes, but keeps it in reserve for near vision. But few persons are willing to do this, inasmuch as vision is very often perfect at a dis- tance without glasses, and in nearly all cases the pa- tient is able, at least during early life, to discern large objects sufficiently well for most purposes. Where, however, there is a high degree of the affection, its subjects usually resign themselves, even from youth, to the use of glasses, and nearly always in advanced age require two pairs, the weaker for distant vision and the stronger for readins;. The latitude of accommodation may be tested by first adapting to the eye such glasses as completely neutralize the hypermetropia, and then measuring the nearest point at which small objects can be distinctly seen. A high degree of hypermetropia is by no means rare in childhood, and is often hereditar}'. Its exist- ence or absence should always be determined by an examination if the eyes readily become fatigued by use. HYPEEMETROPIA. 147 Hypermetropia to a slight extent becomes a normal condition, even in emmetropic eyes, at an advanced age, the far as well as the near point receding from the eye. As Professor Donders was the first to announce the extreme frequence of hypermetropia, so we owe to him the demonstration that this condition of refraction is the visual cause of convergent, as myopia is of di- vergent strabismus. We have seen that the hypermetrope is compelled, even for distant vision, to employ a portion, and often a large portion, of his accommodative power, leaving little to be devoted to the perception of near objects. When, therefore, he has occasion to give his attention for some time to very small and near objects, he en- deavors to reinforce his adaptive power by increased convergence of tlie optic axes. This forced exercise of the internal recti creates after a time a constant ex- cessive action of these muscles ; and the squint, at first only occasional, becomes at last a permanent obliquity. It is thus that strabismus oftenest becomes developed at an age when the child first begins to look at things with intentness. Early performance of an operation for removing the infirmity is extremely important. Otherwise the squinting eye, if one be more affected than its fellow, is thrown out of use, and the impressions made upon its retina, not harmonizing with those in the other eye, soon come to be disregarded ; the perceptive power 148 RECENT ADVANXES IN OPHTIIALMIC SCIENCE. becomes then speedily impaired by disuse, and it can never be restored if the operation be too long de- layed. The use of glasses after the operation ought, in many cases, to be advised, that relapses may not occur from the persistent influence of the hypermetro- pia, the original cause of the deviation. ASTHENOPIA. It has been already remarked that asthenopia, or fatigue of the eye after having been intently used for a long time, often depends upon hypermetropia, which calls for excessive exercise of the accommodative power. It may be relieved, in these cases, by rest and the use of such convex glasses as obviate the necessity for much accommodative effort. It is this accommodative asthenopia which, by inciting. for its partial relief an inordinate action of the internal recti, gives rise to con- vergent strabismus in hypermetropia. A similar ftitigue (asthenopia muBcularis) may also arise from insufficient power of the internal recti mus- cles, in myopic patients, causing them to become read- ily exhausted by efforts at convergence, and favoring the development of divergent strabismus, so commonly associated with myopia. This form of asthenopia may sometimes be reliev^ed by the use of concave glasses for near as well as for distant vision. ASTIGMATISM. 149 Even in a normal eye, too prolonged attention to minute objects may induce similar evidences of fa- tigue, constituting yet another variety of asthenopia, and rest and tonics are often of great service in reliev- ing the symptoms and restoring the ability to bear continuous effort. ASTIGMATISM. We owe to English scientific men, Dr. Youns, Airy the astronomer, and others, the first descriptions of astigmatism, as observed in their own persons ; but these were till lately regarded only as curious and ex- ceptional instances. Professor Donders has recently greatly extended our knowledge of this anomaly of refraction, and pointed out the comparative frequency of its occurrence. Astigmatism results from a want of symmetry in the curvature of the cornea, in consequence of which its refractive power is unequal in different meridians. The images formed by such rays as converge to a focus upon the retina are therefore confused and ren- dered more or less indistinct, in one or the other direc- tion, by the simultaneous formation of a vague circle, or rather oval, of dispersion. A similar irregularity of curvature may exist in the crystalline, giving rise to similar visual disturbance ; but this is of compara- tively rare occurrence. 150 RECENT ADVANCES IN OPHTHAOnc SCIENCE. In nearly all eyes there is a slight variation in tlie refraction of rays in different planes, — the general rule being, tiiat rays entering the eye in a vertical are sooner brought to a focus than those in a horizontal j)lane. The near point is therefore somewhat nearer for horizontal than for vertical lines. This slight de- gree of astigmatism, which may be termed normal, is not sufficient perceptibly to disturb vision. An irrefTular refraction sometimes results from le- sions of the surface of the cornea produced by ulcera- tion, which may cause confused or doi^ble vision in the affected eye. But these deviations are not to be rem- edied by the means which relieve astigmatism, and do not require consideration here. In astigmatic eyes vision is disturbed in such a man- ner that the patient finds it difficult to describe his symptoms ; but on testing his sight, it is evident that it has not the normal acuteness, and that it is improved in a slight degree only by ordinary convex or concave lenses. On desiring him to look at test lines, of equal length and breadth, placed parallel to each other, — some of them in a vertical, some in a horizontal posi- tion, — we find that he sees one set of the lines more clearly than the other. A square appears elongated to a parallelogram, and at the same time less sharply defined in the direction of its length. A small round hole in a screen, behind which is a bright light, seems oval or even linear. If large Roman letters are looked at, at twenty feet distance, some of the lines will be ASTIGMATISM. 151 clearly seen, while those at right angles with the first will appear blurred or of double contours. On looking through a stenopaeic disc, (a metal plate perforated with a narrow slit,) held in a proper direction, the confusion disappears. This forms, perhaps, the readiest method of deter- mining the direction of astigmatism. Its degree is ascertained by placing convex or concave glasses be- fore the slit, until we find with what number vision is clearest. The glasses adapted tp neutralize this abnormal re- fraction are cylindrical in curvature, instead of being ground to a uniform convexity or concavity. Such a glass causes no deviation of rays in the plane of its axis, and this should therefore be placed to correspond with the meridian in which refraction is normal. Rays passing through other planes of the lens will be re- fracted, — those most of all which pass through the meridian at a right angle to the axis, — which is pre- cisely the line of greatest astigmatism. The glasses must be convex cylindrical or concave cylindrical, according as the astigmatism is hyperme- tropic or myopic. If we have no normal meridian, bi-cylindrical or sphero-cylindrical glasses must be employed, the curvature of the two meridians being adapted for those needing rectification in the eye in question. Bi-cjdindrical glasses are appropriate to cases of mixed astigmatism, where one meridian is myopic, the other hypermetropic ; sphero-cylindrical 152 RECENT ADVANCES IN OPHTHALMIC SCIENCE. are suited to compound astigmatism, where both me- ridians have myopic or hypermetropic deviation, but in different deo;rees. One surface of the classes is therefore ground with a spherical curve to correct the simple hypermetropia or myopia, and the opposite surface with a cylindrical curve to correct the astigma- tism. Great care is required in setting cylindrical glasses ; as even a slight want of correspondence between the meridian of deviation and the proper relative po- sition of the glass almost annuls its effect. The glass is to be turned before the eye till the vision becomes clearest, and at this point should be marked by the optician so that it may be set in the frames in pre- cisely the same position. Tlie frames should be well fitted to the wearer, as even a very slight obliquity or tilting of the glasses lessens their beneficial effect. For this reason spectacles are usually to be preferred to eye-glasses, as they keep more steadily their proper position. The cylindrical glasses are required for all purposes ; both near and distant objects seeming blurred and dis- torted without their aid. The pleasure experienced by those who thus, for the first time in their lives, see with perfect distinct- ness, is very great. STRABISMUS. 153 STRABISMUS. The whole pathology of this affection has within a brief period been carefully reinvestigated, with results which have well repaid the attention which has been bestowed. Strabismus is no longer regarded as a mere deformity, but is found to have intimate relations with the function of the eye as an organ of vision. It has been demonstrated, that, as a rule, it is not a primary disease, but, at the outset, merely a symptom, occasioned by certain conditions of refraction ; but it is also proved, that, once confirmed, it may act in its turn, most injuriously, as an efficient cause of dete- rioration and even extinction of visual power. In a large majority of- cases where strabismus has continued for any great length of time, especially where the deviation shows itself usually in one eye, we find that vision is less perfect in the eye most af- fected. This is in consequence of a gradual decline of power, from the fact that the visual axes, (the lines drawn from the macula lutea, in each eye, through the optic centre, towards the object looked at,) cannot be brought simultaneously to bear upon the desired point. Vision is therefore confused, — images of ob- jects being formed upon parts of the retina which do not correspond. To escape, then, the perplexity which results from double siglit, all attempt at binocu- 7* 154 RECENT ADVANCES IX OPHTHALMIC SCIENCE. lar vision is abandoned, and the imiige formed upon the retina of the deviated eye, being received at a point less favorable than the macula lutea for distinct- ness of perception, is disregarded by the brain, till, at length, perceptive power, from lack of exercise, is almost wholly lost in the disused eye. We may ascribe to Professor Bonders our present knowledge of the intimate relation existing between the form of the eyeball and a largo proportion of the cases of strabisnuis ; so that, to translate his own words, " It is only exceptionally that we find conver- gent strabismus without hypermetropia ; and diver- gent strabismus is almost always a consequence of myopia." CONVERGENT STRABISMUS. The almost invariable coexistence of hypermetro- pia with convergent strabismus is explained bv the mutual dependence of the movement of convergence of the internal recti muscles and the act of accom- modation. As in hypermetropia the accommodative power must necessarily be exerted in a high degree, it follows that its associated functidVi, convergence, by which this power is reinforced and enhanced, will be perpetually called into exercise. This takes place in- stinctively, in obedience to the dictates of the " mus- cular sense," as we may term it, — in order that the asthenopia which ensues upon strain of the accommo- CONVERGENT STRABISMUS. 155 dation may be avoided. Being thus brought fre- quently into play, and often maintained .for some time in a state of tension, the recti interni acquire more power, whilst, on the other hand, the external recti, from relaxation and disuse, become relatively feeble. It is probable that the frequency with which the earliest manifestations of strabismus are observed after some of the diseases of childhood, especially after those which have more or less of a nervous element, (as, for instance, whooping-cough, which is perhaps in popular opinion the most common of all the causes of strabis- mus,) may be due to the partial paralysis of the power of accommodation which is often one of the sequelae of these affections. If the disease, followed by this partial paralysis, has supervened about the period when the child first begins to pay close attention to objects, we may readily understand how an effort may be made to compensate for the deficient adaptive power in the ciliary muscle, by increased action of the inter- nal recti in convergence. The same reasons will explain what is termed inter- mitting strabismus, — the deviation only showing it- self when the eyes are looking at near objects, — the very time when accommodation is being called into play. They will also account for another variety of intermitting strabismus, where the obliquity is mani- fested only when the child is fatigued, unwell, or in a state of nervous excitement from fright, diffi- dence, &c. 156 RECENT ADVANCES IN OPHTHALMIC SCIENCE. In these various instances the ciHaiy muscle, receiv- ing an insufficient nervous stimulus, contracts too fee- bly to produce the requisite changes in convexity of the lens, and the accommodative power is therefore instinctively supplemented by the auxiliary action of the internal recti. If we examine each eye singly, screening the other, and direct the patient to look at an object at a dis- tance of a few feet, we find, in cases of ordinary con- vergent strabismus, that either eye is capable of being directed towards the object, while the other eye squints for the time being. This deviation of the more healthy eye is termed the secondary squint, and is in most instances equal in degi'ee to that of the chiefly affected eye ; though, where the strabismus is of long duration, the usually deviated eye is less able than the other to bring its visual line to a given point of the object looked at. The fact that the squinting eye changes its position, and looks forward, as soon as the other eye is screened, proves that it takes little part in ordinary vision. If we test the power of rotation, we observe that both eyes may be turned outwards ; though, from the hypertrophy of the internal and relative atrophy of the external recti, already referred to, they turn less com- pletely in this direction than normal eyes ; for the same reason, they turn inwards to a greater extent than is normal. The movements of the two eyes, used together, are concomitant ; there is no actual CONVERGENT STRABISMUS. 157 paralysis of muscular power ; but the defect lies in a want of harmonious associated action. It is very important to measure the degree of stra- bismus, as this determines whether an operation on one or both eyes will be required, and the extent to which the tendon of the internal rectus should be di- vided. For this purpose an ivory scale, fitted to the form of the eyelid, and graduated in lines and half lines, is convenient. It is placed against the lower lid of the converging eye, and the point where it is crossed by the vertical meridian of the centre or mar- gin of the cornea or of the edge of the pupil, is noted. The other eye is then covered, and the squinting eye now becoming rectified, the number of lines on the scale between the formerly noted point and that now crossed by the same meridian gives the amount ' of deviation. Another mode of measurement is also proposed by Mr. Bowman ; the points compared being, the posi- tion of the outer edge of the cornea in its relation to the external canthus in outward rotation, and tlie position of the pupil as regards the lachrymal punc- tum in inward rotation. Whenever the deviation measures three lines or more it is usually necessary to divide both the inter- nal recti before harmonious action can be re-estab- lished between the eyes. It is well, therefore, to in- form the patient of the probability that an operation on one eye may not be sufficient. 158 RECENT ADVANCES IN OrHTHALmC SCIENCE. The various steps of the operation have been some- what modified by modern surgeons. The incision tlu'ough the conjunctiva should be small, so as to afford as nearly as possible the advantages of a subconjunc- tival operation. The tendon of the muscle should be divided close to its sclerotica! insertion ; unless it be desired to increase the effect of the operation, in which case the muscle may be cut farther back. If it be the intention, on the contrary, to limit the effect to be produced, the tendon may be only partially sev- ered, or a suture may be taken in the conjunctiva to bring together the edges of the external wound. From what has been said of the etiology of conver- gent strabismus, it follows that it must often be neces- sary to prescribe the use of convex glasses, to neutral- ize the hypermetropia, after the strabismus has been rectified by division of the muscle ; that the patient may be secured from a recuri'ence of the deformity, and, especially, that the eye which from long disuse has very imperfect sight, may have its visual power developed and increased. Otherwise, even should no strabismus recur, we have gained only one, and this the least important of the advantages to be derived from the operation ; the deformity is no longer obvi- ous, but the function of one eye still remains more or less dormant, and the patient loses the immense ad- vantages of binocular vision. Even without glasses, it is true, great improvement is often obtained, espe- cially if the patient is intelligent in his endeavors to DIVERGENT STRABISMUS. lijt) bring the eyes into associated use ; but yet more bene- fit ensues when the original defect of refraction is also corrected by suitable lenses. The cases of strabismus depending on opacity of the cornea may be often considered as an attempt of Nature to obviate the effects of the obstruction to the passage of light, by placing the eye in such a position that rays may more readily be transmitted to the ret- ina. Oftentimes, therefore, in such cases, an opera- tion is not called for, or if done, an auxiliary operation should be performed for displacement of the pupil. It is impossible to insist too strongly on the impor- tance of an earhj operation for the relief of strabis- mus, and on the fallacy of the popular belief whicli thinks it probable that " the child may outgrow it," or considers it best to "wait till the child is older" be- fore having anything done. The sight, in thousands of eyes, has been sacrificed to these erroneous opinions. DIVERGENT STRABISMUS. As we have seen, convergent obliquity, resulting from unusual efforts of the internal recti in aid of accommodation in hypermetropic eyes, is most often developed at the age when the influence of hyperme- tropia begins to be felt. Divergent strabismus, on the contrary, associated as it is with the opposite state of refraction, myopia, is a more passive condition, usually 160 RECENT ADVANCES IN OPHTHALMIC SCIENCE. manifesting itself later in life, and perhaps only after occurrence of some of the chanfjes which belons to progressive myopia. The lengthening of the antero-posterior diameter in near-sighted eyes is effected in a great measure by the yielding of the posterior half of the globe, which gives to the eyeball a more or less ovoid form. This brings the centre of rotation farther from the posterior pole of the eye and from the insertions of the muscles, which thus act at disadvantan-e. The movements of the globe are therefore less easy and less extensive than in normal eyes, on account of the difficulty of rotating this ellipsoidal body within the orbital cavity, which has nearly the same form. A greater convergence of the eyes being required as objects are brought nearer, and this convergence having become difficult or impracticable in myopia, from the change of form of the globe and the relative insufficiency of its internal recti muscles, it results, that one eye alone is employed for vision of near objects, while the other is allowed to diverge ; the muscular consciousness, as it may be termed, teaching that a persistent attempt to keep up the convergence merely induces weariness of the internal recti and of the ciliary muscle, without the actual attainment of the advantages of binocular vision. At first, the tendency to diverge shows itself only after the eyes have been fatigued by continued use ; but as the internal recti become more enfeebled, the DIVERGENT STRABISMUS. 161 inclination to yield to the divergent impulse becomes augmented. This is because the strong efforts re- quired in convergence call into play an act of accom- modation on the part of the ciliary muscles, which brings the far point yet nearer, and renders the per- ception of objects less clear. This is by no means agreeable to the patient, and he endeavors to avoid it by giving up binocular vision, and contenting himself with the clearer image formed by a single eye. He in fact unconsciously encourages an outward deviation of one eye, that he may have less annoyance from double images, which associate themselves with his ineffectual efforts to attain the proper degree of con- vergence for the formation of an image upon corre- sponding points of the retina in the two eyes. The fact of the considerable change of form of the globe, and actual relative insufficiency of the internal recti, makes it more difficult to obtain as good a result, as recrards the deviation, from simi)le section of the rectus externus, as may be gained from division of the internal rectus in convergent strabismus. It is fre- quently desirable to keep the eye in a position of forced inversion during the days following the opera- tion, until the externus has formed a reunion with the globe farther back than would take place without this precaution. This may be effected by passing a suture through a fold of the conjunctiva near the inner edge of the cornea, and then through the skin at the inner oanthus. 162 RECENT ADVANCES IN OPHTHALinC SCIENCE. The suture cuts itself out after two or tliree days ; but in the mean time allows opportunity for reattacli- ment of the external muscle in the wished-for posi- tion. The patient should be directed to keep the eyes as quiet as possible during this period, that the suture may not be prematurely torn away. The use of glasses after operation is even more im- portant in divergent than in convergent strabismus, if we wish to obtain everv possible jruarantv acrainst re- lapse; and these should be selected according to the rules previously given in speaking of myopia. INDEX. Accommodation, a physiological ac- tion, 110. anomalies of, 118 apparatus for demonstrating, 32, 106. differs from refraction, 110. in a hypermetropic ej'e, 112. myopic eye, 111. normal eye, 103. instrument for measuring, 117. loss of, after diphtheria, 52. mechanism of, 104, 108. range of. 103. 114. seat of, 104. suspension of, 110. Anaesthetics, in operations on the eye, 35. in operations for cataract, 36. Apoplexy of the retina, 73. Asthenopia, from insufficiencv of in- ternal recti, 124, 148." hypermetropia, 144, 148, 154. prolongeil use of eves for small objects, 149. relieved by glasses, 148. rest and tonics, 149. Astigmatism, corrected by cylindri- cal glasses, 151. from unequal curvatures of cornea, 129, 149. of crystalline, 149. horizontal and vertical lines not seen with equal clear- ness, 150. irregular refraction in differ- ent meridians, 150. mode of determining, 29, 151. Bright's disease, as seen in the ey€, 51. Calabar bean, antagonist to bella- donna, 34. only local means known for contracting the pupil, 34. powers and uses of, 34, 35. Cataract, early diagnosis by lateral illumination, 83. by ophthalmoscope, 83. extraction of, 84. by out-scooping, 84. with iridectomy, 87. linear, 88. by suction, 89. in diabetes, 52. suture after extraction, 90. Choroiditis, affects also the vitreous humor, 78. iride'ctomy in, 79. ophthalmoscopic appearances in, 77. with infiltration of the retina, 78. Ciliary muscle, action of atropia upon, 127. action of calabar bean, 127. artificial paralysis of, 127. function of, 104. loss of power of, 110. spasm of, 128. strabismus in, 126. Conical cornea, iriddesis in, 95. Convergence of the eyes, during ac- commodation, 110. Corel vsis, to detach adhesions of iris^ 46. Cornea, conical, 95. paracentesis of, 39. staphyloma of, 98. syphilitic disease of, 55. Diphtheria, loSs of accommodation after, 52. Diphtheritic inflammation of the conjunctiva, 100. Displacement of the pupil, by irid- desis, 44, 94. by iridectomy, 41, 92. Enucleation of the eyeball, 63. Kxcision of staphyloma, 98. Exophthalmos, with anemia, 48. Eyeball, abnormal tension of, 38, 67. 164 INDEX. Eyeball, elongation of, 131. enuclc'iitioii of, 03. excision of iialf of, G2. stii[)liyloina of, 98. form of, ill hypermctropia,142. myopia, 131. hardness of, in glaucoma, 67. Eye mirror, 4. Ear-point of vision, 102. Glaucoma, acute, 66. chronic, 65. dan