BERKELf Y 
 
 LIBRARY 
 
 owvERSHY or 
 
 CAUfO«WIA . 
 
 fntm TMl 0*TOMIT«IC LiailARY 
 Of 
 
 MONROE JEROME HIRSCH 
 
 A' V3 
 
THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 
 OE CALIEORNIA 
 
 GIVEN WITH LOVE TO THE 
 
 OPTOMETRY LIBRARY 
 
 BY 
 
 MONROE I. HIRSCH, O.D., Ph.D. 
 
CLASSIFICATON 
 
 OF THE 
 
 Motor Anomalies of the Eye 
 
 BASED UPON PHYSIOLOGICAL PRINCIPLES 
 TOGETHER WITH THEIR 
 
 SYMPTOMS, DIAGNOSIS AND TREATMENT 
 
 ALEXANDER DUANE, M.D. 
 
 ASSISTANT SURGEON OPHTHALMIC AND AURAL INSTITUTE, NEW YOFK 
 
 Nbw York 
 
 WILLIAM R. JENKINS CO. 
 
 PUBLISHERS 
 
 851-853 Sixth Avenue 
 1910 
 
(a 
 
 OPTOMETRY 
 
PREFACE, 
 
 
 The following brochure respresents the result of some 
 ten years' labor and- study expended upon the subject of 
 muscular anomalies. Whatever merit it may have is due 
 to the fact that it stands for original investigation in a field 
 still full of difficulties and obscurities. The author's 
 clinical experience has convinced him that the classifica- 
 tions propounded furnishes an adequate working basis for 
 the diagnosis of these conditions. And his experience as 
 a teacher at the Ophthalmic and Aural Institue has led 
 him to believe that the principles here laid down, and the 
 means and methods of examination here recommended, 
 have been found by others also to be both intelligible and 
 practicable. Many of these principles and methods have 
 been enunciated in lectures given to successive classes of 
 practitioners, and have been demonstrated in their prac- 
 tical application upon patients before the same gentlemen ; 
 the auhor's constant attempt being to present clearly and 
 in a way suited to general comprehension the rules for the 
 diagnosis and management of the muscular anomalies. 
 That this attempt was not unsuccessful he has had some 
 reason to believe from the assurances of those that he has 
 taught; and it is, therefore, with th- hope that the result 
 of his work may be useful to others as well that he now 
 offers it to the public. 
 
 Alexander Duane, M. D. 
 
 4ii East Thirtieth tit.. New I'orh. 
 April 'jy, 1S97. 
 
EBBATUM. 
 
 Page 23, line 11: For •'•-!2," read -'L^'/:." 
 
Reprinted from Annals of Ophthalmology and Otology, October, 
 
 A NEW CLASSIFICATION OF THE MOTOR ANOMA- 
 LIES OF THE EYE, BASED UPON PHYSIO- 
 LOGICAL PRINCIPLES. 
 
 THE PRIZE ESSAY OF THE ALUMNI ASSOCIATION OF THE COLLEGE OF I'llY- 
 SICIANS AND SURGEONS, NEW YORK, FOR 1S96. 
 
 By Alexander Duane, M. D., 
 
 NEW YORK. 
 
 ILLUSTRATED. 
 
 Introduction. — Sketch of previous classiflcatious. — Development of 
 the idea of an etiological^ as opposed to a simple anatomical classiti- 
 cation. 
 
 I. Nature of the problems that have to be solved in under- 
 taking a physiological classitication. 
 
 II. The Movements of the Normal Eye. — Actions of the indi- 
 vidual muscles. — Movements of eacii eye individually and the mus- 
 cles by which they are performed. — Amount of these movements. — 
 Field of tixatiou. — Author's experiments. — Power of the individual 
 muscles. — Coordinated movements of the two eyes. — Table of asso- 
 ciated parallel movements and the muscles producing them. — Asso- 
 ciated antagonists. — Field of binocular single vision and of binocular 
 fixation. — Author's experiments. — Movements of convergence. — 
 Power of convergence. — Convergence near-point. — Prism-conver- 
 gence. — Movements of divergence. — Nature of divergence action. — 
 Movements of sursumvergence. — Rotation movements. — Ap- 
 pendix. — Diagrammatic representation of the movements of the eye. 
 
 III. The Tests Employed and Their Significance.— Object of the 
 
 tests. — Tests for l)inocular distant fixation. — Inspection. — Fixation 
 and diplopia tests. — Equilibrium tests — Screen test. — Parallax test. — 
 Tests for associated parallel movements. — Tests for convergence. — 
 Tests for divergence. — Tests for sursumvergence. — Way in which 
 the tests are applied in practice. 
 
 INTRODUCTION. 
 
 The nomenclature and classification of the muscular anomalies 
 of the eye have been passing through the same stages that have 
 been noted in the evolution of the nosology of other parts of the 
 body. In the progress of our knowledge in regard to any given 
 
2 XKW CLASSIFICATION OF MOTOK ANOMALIES. 
 
 set of ailments, the first classification has always been based upon 
 that which first strikes the eye of the observer, namely, the out- 
 ward appearances and symptoms. Thus, many cases of renal dis- 
 ease were first classified as drbpsy, and dropsy formerly figured 
 among physicians, as it does still among the laity, as a substantive 
 disease, and to be treated as such. But, as medical science pro- 
 gressed, and the underlying causes of disease were more and 
 more brought to light, it became evident that dropsy is a symp- 
 tom only and to be treated as a symptom, and that the principles 
 of a rational pathology require us to search for the causes of the 
 dropsy and to institute treatment addressed to the removal of 
 these causes rather than to the direct relief oi the dropsy itself. 
 In this way a pathological classification is gradually substituted 
 for one that is purely symptomatic, and a scientific, casual treat- 
 ment for one that is empirical, or based solely on the. appearances 
 presented. 
 
 This conception of disease as a symptom of a pathological pro- 
 cess, and the consequent conviction that our therapeusis must 
 be based ultimately upon an etiological foundation, could not 
 have developed, or at all events, could not have become anything 
 more than a plausible theory, barren of practical application, were 
 it not constantly fortified by a steady increase in the number and 
 precision of our means of diagnosis. In this way only can we 
 make those fine discriminations between symptoms that enable 
 us to form accurate inferences as to the diverse origin of phenom- 
 ena which, to a cursory observation, seem identical. For exam- 
 ple, our knowledge of the symptomatic nature of dropsy and of 
 the necessity of treating it from an etiological standpoint, how- 
 ever true it might be, would be a theory only, unprovable and 
 practically inapplicable, were it not for the refijied means we now 
 possess for examining the chest and abdomen and for analyzing 
 the urine. These diagnostic means have enabled us to convert 
 theory into fact, and to redeem our treatment from the charge 
 of empiricism. 
 
 A similar process of evolution has taken place in regard to the 
 motor anomalies of the eye. These were formerly (and to a 
 great extent still are) classified simply according to the appear- 
 ances presented, i. e., as inward, outward, upward, or downward 
 deviations. And. to recur to our former illustration, just as 
 dropsy usc<l to be treated as dropsy, regardless of whether it was 
 due to renal, cardiac, or hepatic disease, so an inward squint was 
 (ami often still is) treated simply, as a squint, quite without 
 reference to its origin. The results in both cases have often been 
 disappointing. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 6 
 
 The first great step in advance was taken by Donders, when 
 he demonstrated the frequent connection and apparent causal re- 
 lation between strabismus convergens and hypermetropia, and 
 between strabismus divergens and myopia. And, while subse- 
 quent writers have doubtless gone too far in asserting the univer- 
 sal application of his deductions, the service that he himself did 
 to rational therapeutics by indicating one large class of cases 
 in which a strictly causal treatment relieves the symptoms, can 
 scarcely be overestimated. 
 
 Another exceedingly important advance made was in the dis- 
 covery of the insufficiencies and of the methods of estimating 
 them. These latter, devised by V. Graefe, remain to-day among 
 the chief means of discriminating between the various motor 
 anomalies; and their invention, as in the case of all new methods 
 of precision, opened the way to still further discoveries. 
 
 The diagnosis ajid symptomatology of paralytic deviations was 
 also worked out by the same author, and in a manner so admira- 
 bly complete, that little remained for his successors to do ex- 
 cept to gather statistics in regard to the precise etiology of these 
 interesting affections. 
 
 V. Graefe had pointed out the relation between insufficiency 
 and squint, but since his time this relation has been largely over- 
 looked, the consequence being that the two conditions have of- 
 ten been classed as categorically distinct, and distinct principles 
 of treatment have been applied to them. This arbitrary separa- 
 tion of two things really the same has had a retarding influence 
 upon the development of our knowledge of muscular anomalies. 
 
 It toecame, after awhile, apparent that the very term insuffi- 
 ciency was a defective one, implying, as it did, a casual relation, 
 which was by no means always present. Hence, Stevens in this 
 country proposed a system of classification in which the term in- 
 sufficiency was replaced by Jiderophoria. and the term strabis- 
 mus by heterotrofia. the former indicating a tendency to de- 
 viation, which tendency is habitually overcome, and the latter 
 a deviation which is more or less constantly present. 
 The further use of the prefixes Eso-, Exo-, and Hyper-, served 
 to differentiate between deviations or tendencies inward (con- 
 vergent deviation), outward (divergent deviation), and upward 
 for, more properly, divergence in a vertical plane). This classi- 
 fication is extremely convenient and has been generally accepted, 
 at least in America. Furthermore, the instruments of precision, 
 which the same author devised for measuring the various devia- 
 tions, are doubtless the best extant, and have greatly facilitated 
 the recognition and differentiation of the anomalies in question. 
 
4 NEW CLASSII-ICATION OF MOTOR ANOMALIES. 
 
 Stevens also did sen^ice in pointing out that many cases of so- 
 called insufficiency, or heterophoria, were really low degrees of 
 squint — a fact which, as already stated, has been too much over- 
 looked. 
 
 He further called particular attention to the importance and 
 frequency of the vertical deviations which had received (and, in 
 fact, still receive) too little notice; the fact being that their recog- 
 nition and correction are very necessary features in the manage- 
 ment of many cases of muscular trouble. 
 
 Stevens' classification, however, is open to the serious objec- 
 tion that it reinstates the idea of grouping deviations according 
 to their anatomical characters and puts the etiological element 
 in the background. Tliat is, it aims to classify motor disorders 
 according to their outward, visible characters, and not according 
 to their cause. In this way, though admirable in other respects, 
 it would seem to be a distinct step backwards. Thus, while the 
 term insufficiency is faulty, because it restricts too narrowly our 
 conception of the possible etiology of a given motor affection, 
 the term heterophoria is objectionable, because it throws away 
 the etiological idea altogether, and once more directs our atten- 
 tion simply to the appearances present, i. e., to the fact that the 
 eye in a certain case deviates up, down, out, or in. To be sure, 
 this has its advantages in that there are many cases in which we 
 cannot say at once, or even after considerable testing, what the 
 true condition underlying these appearances is, and we have, 
 therefore, to content ourselves with a provisional — i. e., an anat- 
 omical — diagnosis. But we should always feel that such a diag- 
 nosis is provisional, and that a really satisfactory diagnosis 
 should express the cause of the deviation as well as its char- 
 acter. That is, the statement that in a given case so many de- 
 grees of esophoria were found should be regarded as only an in- 
 complete presentation of the facts; the final diagnosis not being 
 reached until we have determined the cause of the esophoria, i. e., 
 have made out which one of the many and complex functions 
 of the neuro-muscular apparatus of the eye is deranged. In the 
 meantime, the terms that Stevens has devised are very conven- 
 ient for puri:)oscs of record and for indicating the provisional di- 
 agnosis. 
 
 The next step naturally left to take — the classification, namely, 
 of the motor affections of the eye upon an etiological basis — has 
 been but partially made. Apart from Bonder's researches be- 
 fore mentioned, and V. Graefe's demonstrations of the characters 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 displayed by paretic squint, the main contributions to the sub- 
 ject have been A. Graefe's description of convergence-insuffi- 
 ciency, Landolt's observations upon the comparative effect and 
 relative value of advancement and tenotomy in the treatment of 
 various kinds of strabismus, and some of Stevens' recent papers. 
 Nowhere, however, have the observations bearing upon this 
 point been properly co-ordinated, so as to form a complete classi- 
 fication of all the different anomalies, founded upon a strictly eti- 
 ological and physiological basis. To do this, at least in part, is 
 the object of the present essay, which is based almost exclusively 
 upon observations made by the author himself during the past 
 ten years. The subject has seemed to him to be one not only of 
 scientific interest, but also of great practical importance, since, 
 as experience has shown, our plans of treatment are necessarily 
 largely modified by our notions of the real nature and causes of 
 the condition that we are called upon to correct. Moreover, the 
 cases themselves are very numerous; their symptoms, subjective 
 and objective, are multiform and complex; while the results of 
 treatment, which are often brilliant, are often also disappointing, 
 owing, no doubt, frequently, to our ignorance of the exact na- 
 ture of the case before us. It has seemed proper, therefore, to 
 enter into considerable detail in trying to determine what should 
 be the proper classification of such cases, and what precisely are 
 the differential marks by which they can be distinguished one 
 from the other. 
 
 I. 
 
 NATURE OF THE PROBLEM. 
 
 The task that confronts us when we attempt to make any classi- 
 fication of the kind now essayed is that of framing a scheme by 
 reference to which the following problem may, in most instances, 
 at least, be resolved : Given a case zutth a certain train of symp- 
 toms^ to determine the ultimate cause of these symptoms^ i. e., 
 the part or function that is primarily deranged^ and the manner 
 of its derangement. The solution of this problem obviously pre- 
 supposes, first, an accurate knowledge of the normal state of the 
 various parts and functions that may be involved, and, second, 
 a consideration of the different means we have for determining 
 whether each part or function is actually normal or not. Thus, 
 in the case of deformities about the hip, a proper classification, i. 
 e., one which tells us whether any given deformity is due to a 
 fracture, to a dorsal dislocation, or to hip-disease, is possible only 
 after we have become thoroughly acquainted with the normal re- 
 lations and movements of the hip-joint, and with the means at our 
 
G NEW CLASSIFICATION- OK MOTOR ANOMALIES. 
 
 coinmand for appreciating the various deviations from the nor- 
 mal and their significance. Applying this principle to the eye, 
 ^ve may say that the solution of our problem is contained in the 
 answers to the following questions: 
 
 (1). What are the different normal functions of the neuro- 
 muscular apparatus of the eye, and what is their anatomical 
 seal? 
 
 (2). In \\hat way is it possible for these functions to be de- 
 ranged ? 
 
 (3). \Miat means have \vc for telling whether any special func- 
 tion is deranged or not, and, if so, what the nature of the derange- 
 ment is? 
 
 (4). What are the conditions actually met wdth in practice, 
 and how do they correspond to the scheme that w-e have framed? 
 
 The consideration of these questions we will now take up in the 
 order named. 
 
 II. 
 
 MOVEMENTS OF THE jSTOKMAL EYE. 
 The functions concerned in the group of cases under consid- 
 eration comprise (a) the actions of the individual nntscles that 
 are inserted into the eyeball ; (<5) the ?uovcments possible to each 
 eye separately through the individual or concerted working of 
 these muscles and (c), the character and extent of the move- 
 ments actually performed by the tzvo eyes when acting together. 
 
 The actions of the individual muscles are best exhibited in 
 tabular form, as follows: 
 
 
 
 end 
 ridi- 
 
 (tor- 
 
 i-s-: 
 
 III 
 
 
 0.2 
 
 §s 
 
 
 Field of 
 
 &ilps^ 
 
 
 Hi 
 
 > 
 
 57 
 
 ■■Sg 
 
 1.2-2 
 
 Muscle 
 
 action 1^2 s? ^^ 
 
 Lateral a 
 sional eff. 
 creasing a 
 
 I 
 
 II 
 
 * "3.2 >> 
 
 
 limited to > ii 
 
 llll 
 Pi o « 
 
 Lateral; 
 effects 
 ingto Z( 
 ; is 
 
 it 
 
 II 
 
 External 
 
 Outer half of ' Out 
 
 No ac- 
 
 
 
 No ac- 
 
 
 
 Rectus. 
 
 field of fixation} 
 
 tion 
 
 
 
 tion 
 
 
 
 Internal 
 
 Inner half of 
 
 In 
 
 No ac- 
 
 
 
 No ac- 
 
 
 
 Rectus. 
 
 field of fixation 
 
 
 tion 
 
 
 
 tion 
 
 
 
 Superior 
 
 Upper half of 
 
 In 
 
 in 
 
 Adduct- 
 
 Abduct- 
 
 Up 
 
 Abduct - 
 
 Ad- 
 
 Rectus. 
 
 field of fixation 
 
 
 ed. 
 
 ed. 
 
 
 ed. 
 
 ducted 
 
 Inferior 
 
 Lower half of In 
 
 Out 
 
 Adduct- 
 
 Abduct- 
 
 Down 
 
 Abduct- 
 
 Ad- 
 
 Rectus. 
 
 field of fixation 
 
 cd. 
 
 ed. 
 
 
 ed. 
 
 ducted 
 
 Superior 
 
 Lower half of Out 
 
 In 
 
 Ab.liut- 
 
 .\(ld.K-l- 
 
 Down 
 
 Ail.luct- 
 
 Ab- 
 
 oblique 
 
 field of fixation 
 
 
 id. 
 
 cd. 
 
 
 td. 
 
 ducted 
 
 Inferior 
 
 Upper half of Out 
 
 Out 
 
 Abduct- 
 
 Adduct- 
 
 Up 
 
 Adduct- 
 
 Ab- 
 
 Oblique 
 
 field of fixation 
 
 
 ed 
 
 ed. 
 
 
 ed. 
 
 ducted 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. < 
 
 It will be seen from the foregoing table that, under ordinary 
 conditions the only two muscles which precisely counteract one 
 another's action, or which are, in the language of physiology, 
 direct antagonists, are the external and internal recti. 
 
 The superior and inferior recti, for example, are only partially 
 antagouistic, for. while respectively elevatiug and depressing tlie 
 eye, so as to be directly opposed to each other in this regard, and 
 while 'tlieir action in rotating the vertical meridian of the cornea 
 is also precisely opposite, they both adduet the eye. Hence, when 
 acting together they will reinforce the internal rectus, and this 
 action will be most strongly pronounced Avhen the eye is already 
 markedly adducted, i. e., under conditions in which the internal 
 rectus is Avorking at some mechanical disadvantage. The like is 
 true O'f the combined action of the two obliques, which neutralize 
 each other as far as rotation of the vertical meridian and as far 
 as elevation and depression are concerned, but work 'together in pro- 
 ducing abduction and hence assist the extei-nal rectus, especially 
 Avheu the eye is already strongly abducted. On the other hand, 
 when the eye is strongly adducted, the lateral action of the two 
 obliques falls away, and these two muscles act siimply to elevate and 
 depress the eye respectively. In this position, therefore, they do 
 neutralize each other perfectly, and are direct antagonists. The 
 saime is true of the superior and inferior recti when the eye is ab- 
 ducted. For further remarks upon this subject, see the appendix 
 to this chapter. 
 
 Almost every movement that the eye can make requires the 
 combined action of at least two of the ocular muscles. Thus to 
 lift the eye straight upwards, we must use both the superior 
 rectus and the inferior oblique. 
 
 The superior rectus, acting by itself, would carry the eye inward 
 as well as upward, and would rotate the vertical meridian of the 
 cornea inward. So, too, the inferior oblique, acting by itself, would 
 tend to abduct the eye and rotate the vertical meridian outward. 
 Neither, therefore, alone will carry the eye straight upward, but 
 the two acting together, will neutralize each other as far as their 
 lateral working and their effect upon the vertical meridian are con- 
 cerned, and consequently the eye rises vertically, without swerving 
 to the right or left, and without any deflection of its vertical 
 meridian. 
 
 It is probable that the external and internal recti assist in main- 
 taining the strict verticality of this movement, their simultaneous 
 contraction steadying the eye and preventing it from swerving. In 
 this case, therefore, at least two, and probably four muscles, are 
 concerned in the movement. 
 
 Similarly, depression of the eye is always accomplished by the 
 conjoint action of the inferior rectus and the superior oblique, 
 which neutralize each other to a greater or less extent, as far as 
 their lateral working and their effect upon the vertical meridian 
 are concerned, but which assist each other in carrying the eye 
 downward. Here. too. probably the external and internal recti come 
 into play as steadying and supporting factors. 
 
 Even in so simple a movement as that of abduction, which might 
 be performed by a single muscle, it is probable that at least two 
 
8 XK\V CLASSIFICATION OF MOTOU ANOMALIES. 
 
 (i. e.. both obliques), or even four other niuseles (i. e., all except 
 the internus), take part either in reinforcing the action, or in steady- 
 ing the eye and rendering the movement uniform. 8e<^ Appendix. 
 
 The nioveiiiciits of the individual ocular muscles are, as is well 
 known, presided over by more or less discrete nuclei scattered 
 along the walls of the third ventricle, aqueduct of Sylvius, and 
 fourth ventricle; but the precise method in w^hich these are ar- 
 ranged and inter-connected has not yet been sufficiently deter- 
 mined. 
 
 The Movements Possible to the Eye through the co-ordi- 
 nated action of its six muscles comprise rotations in every con- 
 ceivable plane, the eye being capable of moving from the primary 
 position directly to any secondary position, and from the latter 
 again to any other secondary position, and in so doing may take 
 either a direct or a sinuous course.* The typical direct move- 
 ments from the primary position, together with the muscles con- 
 cerned in the production of these movements, are shown in the 
 following table : 
 
 *This may be proved by making two fine dots upon a card, so 
 close together that unless very accurately fixed (i. e., if seen ever so 
 slig"htly in diffusion circles), they will blend into one. and then mov- 
 ing the card slowly in all directions before the eye. the head re- 
 maining fixed. However the card is moved, the two dots will re- 
 main distinct, thus showing that the eye follows them in all their 
 movements. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 o S P. a 
 
 (Abduc- 
 tiou) 
 
 (Adduc- 
 tion.) 
 
 Move Eye 
 Laterally* 
 
 Syner- 
 gists. 
 
 Superior 
 Oblique 
 
 Inferior 
 Oblique 
 
 Oppo- 
 nents. 
 
 Superior 
 Rectus. 
 
 Inferior 
 Rectus. 
 
 Move Eye 
 Vertically* 
 
 Rotate Upper 
 End of Verti- 
 cal Meridan 
 of Cornea* 
 
 No action. No action, 
 
 Out 1 Action 
 I increas 
 I ing the! 
 y further 
 
 Out 1 the eye 
 I i.s ab- 
 J ducted. 
 
 Down] 1 Action 
 I equal 
 I and op- 
 posite; 
 j-decreas 
 [Up] ing the 
 more 
 
 [Out] 
 
 the eye 
 
 I ■ 
 
 is ab- 
 ducted. 
 
 [In] 
 
 [In] 
 
 "I Actions 
 
 I slight ! [UpJ 
 
 I and de- 
 
 ! creas- 
 
 Hng the 
 
 I more I 
 
 the eye [Down 
 I is ab- 
 J ducted. 
 
 ] Actions 
 1 equal 
 I and op- 
 I posite; 
 1 increas 
 [ing the 
 I more 
 I the eye 
 I is ab- 
 J ducted. 
 
 Ilnternal ! 
 I Rectus 
 
 Syner- 
 gists.] 
 
 Superior 
 Rectus 
 
 Inferior I 
 Rectus 
 
 Oppo- 
 nents. 
 
 In 
 
 Action 
 increas- 
 ing thel 
 • more I 
 the eye 
 is ad- 
 ducted. 
 
 [In] 1 Actions 
 I equal 
 and 
 I oppo- 
 ' site; 
 increas 
 ing the 
 
 I the eve 
 I is ab- 
 J ducted. 
 1 Actions 
 
 equal 
 
 and 
 [In] I oppo- 
 I site; 
 f decreas 
 I ing the 
 I more 
 [Out] i the eye 
 1 is ab- 
 j ducted. 
 
 No action. 
 
 Superior j [Out] 1 Action 
 Oblique I slight 
 
 ! I and di- 
 
 minish- 
 
 Inferior j fO"t] 
 Oblique! 
 
 "I Action* 
 [Up] I equal [In] 
 I and op- 
 f posite; 
 f decreas 
 ;Down] I ing as [Out[ 
 ' the eye 
 
 Action 
 equal [In] 
 
 and op- 
 posite; 
 
 increas 
 
 ing as 
 the eye 
 is ad- 
 ducted, 1 
 
 [Up] 
 
 mg as 
 
 the eye [Out] 
 is ad- I 
 ducted. ' 
 
 I 
 
 1 Actions 
 
 equal 
 
 I and op- 
 
 I posite;! 
 
 'ncreas 
 
 ducted. 
 
 Actions 
 equal 
 and op- 
 posite: 
 dimin- 
 ishing 
 as eye 
 is ad- 
 ducted. 
 
 Resultant 
 
 Effect Upon 
 
 Eye. 
 
 Eye carried 
 out mainly by 
 action of ex- 
 ternal rectus 
 assisted by the 
 two obliques ; 
 the effect of 
 the latter be- 
 ing the greater 
 the more the 
 eye is abduct- 
 ed. The op- 
 posing (ad- 
 ducting) ac- 
 tion of the su- 
 perior and iu- 
 ferior recti 
 also dimin- 
 ishes as the 
 eye is abduct- 
 ed. The eye 
 is steadied 
 and its verti 
 cal meridian 
 kept vertical 
 by the traction 
 exerted by 
 the superior 
 and inferior 
 recti and the 
 two obliques. 
 
 Eye carried in 
 mainly by in- 
 ternal rectus, 
 assisted by the 
 superior and 
 inferior recti: 
 the effect of the 
 latter being 
 greater, the 
 more the aye 
 is adducted. 
 
 The opposing 
 (abducting)ac- 
 tion of the two 
 obliques dim- 
 inishes as the 
 eve is adduc- 
 ted. The eye 
 is steadied and 
 its vertical me- 
 ridian kept 
 vertical by the 
 counterpois- 
 ing action of 
 the two obli- 
 ques and the 
 superior and 
 inferior recti. 
 
 * Movements that are completely neutralized by the action of opposi 
 muscles are placed in brackets. 
 
10 
 
 NEW CLASSIFICATION OK MOTOH ANOMALIES. 
 
 •r «~ Vi 'C O 
 
 fi o Sb^ 
 
 Up 
 (SuTsum- 
 duction) 
 
 Muscles 
 
 Con- 
 cerned. 
 
 Move Eye 
 Laterally 
 
 Rotate Upper d »» » 
 
 Move Eye ,End of Vertical pS^^J^\^°' 
 
 Vertically Meridian of ^,uli}^^ 
 
 Cornea | the Eye 
 
 Superior [In] 1 Move- Up. 
 
 Rectus ments ■ 
 
 Inferior > equal ! 
 
 Oblique [Out] I and op- Up. 
 J posite.i 
 
 Syner- I 
 gists. 
 External [Out] 
 , Rectus 
 
 [In] 
 
 Diagon- 
 ally Up 
 and Out. 
 
 Internal 
 Rectus 
 Superior [In] 
 
 Rectus slight and dim- 
 inishing as eye 
 is abducted. 
 
 Actions No action 
 
 equal 
 and 
 
 oppo- No action 
 site^ ! 
 
 Action 
 
 [In] 1 Actions 
 I equal 
 [andop- 
 
 [Out[ J posite. 
 
 No action 
 
 Up, Action [In] ; Action, 
 
 marked and in- slight and dim- 
 creasiug as eye inishing as eye' 
 bducted. is abducted. 
 
 Inferior 
 Oblique 
 
 Out; Action Up; Action Out : Action 
 increasing as slight and de- marked and in- 
 eye is abduc- creasing as eye creasing as eye 
 ted- is abducted. is abducted. | 
 
 Diagon- 
 ally Up 
 and In. 
 
 Superior I In: Action Up; Actionl In: Action 
 
 Rectus increases as slight and de- increases as 
 
 jeye is carried creasing as eye eye is carried 
 
 linward. is adducted; 
 
 finally U. 
 
 Inferior [Out]; Action Up; Action [Out] Action 
 Oblique slight and de- marked and slight and de- 
 creasing as eye increasing as'creasing as eye 
 is carried in. eye is carried is carried in. 
 in. I 
 
 Internal In. 
 Rectus. 
 
 Eye carried 
 straight up: 
 vertical meri- 
 dian remains 
 vertical. The 
 counterpois- 
 ing actiou of 
 the internal 
 and external 
 recti serves to 
 steady eye and 
 keep it in the 
 vertical line- 
 Eye carried 
 up mainly by 
 superior rec- 
 tus, the elevat- 
 ing action of 
 this muscle in- 
 creasing and 
 that of the in- 
 ferior oblique 
 diminishing as 
 the eye is Jib- 
 ducted. Eye 
 carried out 
 
 mainly by ex- 
 ternal rectus, 
 ' assisted by in- 
 ferior oblique, 
 
 especially 
 when abduc- 
 tion is marked. 
 Vertical meri- 
 dian rotated 
 out. 
 Eye carried up 
 mainly by the in- 
 ferior obliciue, the 
 elevating action of 
 this muscle in- 
 creasing and that 
 of the superior rec- 
 tus decreasing as 
 the eye is adduc- 
 ted. Eye carried 
 i» by the internal 
 rectus, assisted, 
 especially when 
 adduction is mar- 
 ked, by the super- 
 ior rectus, Vertical 
 meridian rotated 
 
 Down 
 
 ! Inferior ] [In] "1 Actions 
 
 Rectus 1 equal 
 Superior [Out] land op- 
 
 Down. 
 
 [Out] 1 Action 
 
 The eye carried 
 
 (Deor- 
 
 
 [equal straight down, ver- 
 
 sumduc- 
 
 Down. 
 
 [In] landop-tical meridian re- 
 
 tionj 
 
 Oblique. J posite. 
 
 Si/ner- 
 gists 
 
 
 J posite. 
 
 maining vertical. 
 External and in- 
 ternal recti by 
 their counter- 
 
 
 External [Out] ) Actions 
 
 No action. 
 
 No action. 
 
 traction serve to 
 
 
 Rectus. 1 equal 
 
 
 [steady eye and 
 
 
 Internal [In] | andop- 
 
 No action. 
 
 No action. keep it in the ver- 
 
 
 Rectus. 1 J posite. 
 
 
 tical line. 
 
NEW CLASSIFICATION OF MOTOH ANOMALIES. 
 
 11 
 
 Muscles 
 Con- 
 cerned. 
 
 Move Eye 
 Laterally. 
 
 Move Eye 
 Vertically. 
 
 Rotate Upper 
 End of Verti- 
 cal Meridi- 
 an of Cor- 
 nea. 
 
 Resultant Effect 
 Upon Eye. 
 
 Diagon- 
 ally 
 Down 
 and Out 
 
 Superior. 
 Oblique 
 
 External 
 Rectus. 
 
 [Inj ; Action 
 slight and dim- 
 inishing as eye 
 is abducted. 
 
 Out; Action 
 increasing as 
 eye is abduc- 
 ted. 
 
 Down; Ac- [Out]; Ac- 
 tion marked ition slight and 
 and increasing diminishing as 
 as eye is ab- eye is abduc- 
 ducted. ted. 
 
 Down: Ac- In; Action 
 tion slight and increasing as 
 diminishing as eye is abduc- 
 eye is abduc- ted. 
 ten. 
 
 No action No action. 
 
 The eye carried 
 doirn mainly by 
 inferior rectus, 
 the depressing ac- 
 tion of this muscle 
 increasing and 
 
 that of the super- 
 ior oblique fle- 
 creasing as the 
 eye is abducted. 
 Eye carried out 
 mainly by external 
 rectus. assisted 
 especially in ex- 
 treme abduction, 
 by the superior 
 oblique. Vertical 
 meridian rotated 
 
 Diagon- 
 ally 
 Down 
 and In. 
 
 Superior I [Out;] Action 
 Oblique, slight and dim- 
 inishing es eye 
 is adducted. 
 
 Rectus increasing as 
 eye is adduc- 
 ted. 
 
 Internal In. 
 Rectus. 
 
 Down; Ac-| I In;] Action 
 tion marked] slight and dim- 
 and increasing, inishing as eye 
 as eye is car- is adducted 
 ried inward 
 
 Down; Action Out; Action 
 light and dim-iincreasing as 
 inishing as eyejeye is adduc- 
 is adducted. ted. 
 
 The eye carried 
 doivii mainly by 
 the superior obli- 
 que, the depress- 
 ing action of this 
 muscle increasing 
 and that of the in- 
 ferior rectus dim- 
 inishing as the eye 
 is adducted. Eye 
 carried in mainly 
 by the internal 
 rectus, assisted 
 especially in ex- 
 treme adduction 
 by the inferior 
 rectus; vertical 
 meridian rotated 
 out. 
 
 The amount that the eye can move in each one of the direc- 
 tions specified maybe determined experimentally by placing the 
 subject experimented upon with his eyes in the primary position 
 and directed at an object whose recognition implies accurate fix- 
 ation, (e. g.) a fine double dot on a card, and then moving the 
 object in the given direction, requiring the patient at the same 
 time to follow it with his eyes, but not with his head. The 
 moment when he ceases to follow it will be evidenced objec- 
 tively by the perceptible wavering of the eye, which hitherto 
 had steadily followed the object, and subjectively by the fact 
 that the object itself becomes confused and no longer recog- 
 nizable. Then the arc through which the eye has rotated in 
 passing from the primary to the terminal position may be 
 measured either roughly with the eye, or accurately by some 
 form of perimeter.* 
 
 *This may also be accomplished by Stevens' tropometer or some 
 similar instrument which measures the rotation of the eye by meas- 
 uring the arc traversed by the corneal reflex. 
 
12 
 
 XKW CLASSIFICATION OK MOTOR ANOMALIES. 
 
 By ascertaining the limits of movement in all directions, we de- 
 fine the boundaries of the field of fixation \. e., of the entire space 
 through which the visual line can be carried without moving the 
 head. 
 
 The measurement of the field of fixation in any given case re- 
 quires that the patient under examination shall, in each excur- 
 sion that he makes with his eyes, put forth the maximum efifort 
 of which he is capable. This he will frequently fail to do, thereby 
 making the field appear incomplete. It is only by making sev- 
 eral examinations and taking the maximum of all the measure- 
 ments, that we arrive at a perfectly reliable result, i. e., one which 
 shows the full extent of excursion of which the eye is capable. 
 The discrepancies thus obtained in repeated examinations are 
 well shown in cases 1, 5, and 6, of the following table, which is 
 constructed from observations of my own, made upon normal 
 eyes with the perimeter, and using the fine double dot as a test- 
 object. 
 
 
 
 
 RIGHT RYES* 
 
 
 
 
 Case. 
 
 rp 
 
 Up & Out 
 
 Up & In 
 
 Out 
 
 In 
 
 Down 
 
 Down & Out 
 
 Down & In 
 
 1 1st exam. 
 
 40 
 
 35 
 
 40 
 
 35 
 
 40 
 
 70 
 
 33 
 
 J5 
 
 .. 2d exam. 
 
 38 
 
 45 
 
 40 
 
 48 
 
 48 
 
 42 
 
 55 
 
 50 
 
 2 
 
 40 
 
 50 
 
 40 
 
 
 
 45 
 
 60 
 
 60 
 
 3 
 
 50 
 
 45 
 
 55 
 
 55 
 
 45 
 
 60 
 
 65 
 
 55 
 
 4 Right eye not 
 
 examined. 
 
 
 
 
 
 
 
 5 1st exam. 
 
 40 
 
 4S 
 
 (50) 
 
 60 
 
 (50) 
 
 62 
 
 65 
 
 (50) 
 
 " 2d exam. 
 
 40 
 
 4S 
 
 (55) 
 
 50 
 
 (55) 
 
 (62) 
 
 50 
 
 (60) 
 
 "3rd exam. 
 
 (30) 
 
 42 
 
 (42) 
 
 50 
 
 (45) 
 
 60 
 
 65 
 
 (60) 
 
 6 1st exam. 
 
 32 
 
 45 
 
 32 
 
 52 
 
 52 
 
 
 65 
 
 50 
 
 " 2d exam. 
 
 38 
 
 
 50 
 
 
 
 
 
 
 7 
 
 32 
 
 35 
 
 35 
 
 55 
 
 52 
 
 72 
 
 65 
 
 (62) 
 
 8 
 
 44 
 
 55 
 
 55 
 
 60 
 
 60 
 
 62 
 
 70 
 
 (65) 
 
 9 
 
 50 
 
 50 
 
 60 
 
 52 
 
 (60) 
 
 80 
 
 (70) 
 
 60 
 
 10 
 
 40 
 
 40 
 
 42 
 
 50 
 
 42 
 
 45 
 
 50 
 
 40 
 
 11 1st exam. 
 
 47 
 
 50 
 
 50 
 
 40 
 
 63 
 
 63 
 
 67 
 
 55 
 
 12 Right eye not examined 
 
 I. 
 
 
 
 
 
 
 13 
 
 45 
 
 55 
 
 (55) 
 
 50 
 
 60 
 
 55 
 
 52 
 
 (53) 
 
 14 1st exam. 
 
 52 
 
 60 
 
 55 
 
 52 
 
 50 
 
 62 
 
 60 
 
 55 
 
 .. 2d exam. 
 
 40 
 
 50 
 
 (45) 
 
 65 
 
 (50) 
 
 65 
 
 SO 
 
 (50) 
 
 15 
 
 (50) 
 
 45 
 
 52 
 
 48 
 
 56 
 
 62 
 
 58 
 
 (60) 
 
 16 1st exam. 
 
 52 
 
 50 
 
 55 
 
 48 
 
 56 
 
 60 
 
 60 
 
 (50) 
 
 17 1st exam. 
 
 40 
 
 38 
 
 50 
 
 40 
 
 (45) 
 
 68 
 
 (65) 
 
 (50) 
 
 .. 2d exam. 
 
 47 
 
 52 
 
 52 
 
 48 
 
 (4S) 
 
 60 
 
 (40) 
 
 60 
 
 18 
 
 60 
 
 70 
 
 62 
 
 75 
 
 60 
 
 65 
 
 73 
 
 60 
 
 •Figures enclo.sed in parentheses mean that at this point the test object disappear- 
 ed from view behind some projecting part of tlic face, but at tlic time of disappear- 
 ance was still within the field of fixation. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 13 
 
 
 
 
 LEFT EYES. 
 
 
 
 
 Case 
 
 rp I 
 
 •p & Out 
 
 Up& I 
 
 n Out 
 
 In 
 
 Down 
 
 Down & Out 
 
 Down & 
 
 1 1st exam. 
 
 .^^l 
 
 40 
 
 45 
 
 35 
 
 45 
 
 70 
 
 60 
 
 50 
 
 .. 2d exam. 
 
 42 
 
 40 
 
 55 
 
 48 
 
 60 
 
 70 
 
 50 
 
 60 
 
 2 
 
 40 
 
 50 
 
 40 
 
 
 
 60 
 
 50 
 
 60 
 
 3 
 
 35 
 
 40 
 
 45 
 
 55 
 
 50 
 
 65 
 
 
 75 
 
 4 
 
 40 
 
 38 
 
 46 
 
 48 
 
 40 
 
 35 
 
 38 
 
 32 
 
 5 1st exam. 
 
 40 
 
 52 
 
 42 
 
 53 
 
 [48] 
 
 65 
 
 70 
 
 [50] 
 
 .. 2d exam. 
 
 43 
 
 50 
 
 [44] 
 
 52 
 
 48 
 
 [68] 
 
 62 
 
 [48] 
 
 i. 3rd exam 
 
 42 
 
 50 
 
 40 
 
 48 
 
 [50] 
 
 65 
 
 60 
 
 [50] 
 
 6 Left eye : 
 
 not examined. 
 
 
 
 
 
 
 
 7 
 
 35 
 
 42 
 
 45 
 
 55 
 
 52 
 
 70 
 
 65 
 
 60 
 
 S Left eye not examined. 
 
 
 
 
 
 
 
 9 
 
 55 
 
 60 
 
 60 
 
 58 
 
 60 
 
 72 
 
 75 
 
 [40] 
 
 10 Left eye 
 
 not examined. 
 
 
 
 
 
 
 
 11 1st exam. 
 
 50 
 
 45 
 
 55 
 
 47 
 
 60 
 
 65 
 
 68 
 
 60 
 
 12 
 
 50 
 
 60 
 
 50 
 
 50 
 
 [60] 
 
 70 
 
 62 
 
 [40] 
 
 13 
 
 [40] 
 
 55 
 
 50 
 
 50 
 
 [50] 
 
 60 
 
 75 
 
 
 14 1st exam. 
 
 46 
 
 60 
 
 55 
 
 55 
 
 45 
 
 72 
 
 72 
 
 60 
 
 .. 2d exam. 
 
 
 
 
 
 
 
 
 
 15 
 
 48 
 
 50 
 
 50 
 
 56 
 
 55 
 
 65 
 
 60 
 
 [60] 
 
 16 Is exam. 
 
 48 
 
 55 
 
 52 
 
 55 
 
 52 
 
 60 
 
 55 
 
 • 52 
 
 17 1st exam. 
 
 40 
 
 42 
 
 [50] 
 
 40 
 
 62 
 
 70 
 
 60 
 
 [52] 
 
 IS 2d exam. 
 
 44 
 
 50 
 
 50 
 
 48 
 
 [50] 
 
 62 
 
 62 
 
 [40] 
 
 
 • 58 
 
 71 
 
 71 
 
 72 
 
 62 
 
 72 
 
 76 
 
 68 
 
 The average of the observations above tabulated gives ratlier a 
 larger field of fixation than has been obtained by other experi- 
 menters. Thus, Landolt's figures, vs^hile showing a close agreement 
 for excursions in the upper field, are appreciably less for movements 
 downward (about 50° in looking down, 38° in looking down and 
 out, and 47° in looking down and in). On the other hand, the ex- 
 periments of Schuurmann and Uonders give the range of downward 
 excursion as 57°, which is somewhat less than those that were 
 found by me, but the upward excursion as only 34°. This latter 
 figure certainly seems too small, in view of the fact that in but 
 one of my cases was the range as low as this, and that in nearly 
 all the others it fluctuated between 40° and 50°.* 
 
 From the range of excursion of the eye in various directions, 
 we can form a tolerably close estimate of the amotitit of xvork 
 that each muscle does in moving the eye. 
 
 For example, when the eye is abducted 30°-35°, its movement up- 
 wards is effected solely by the superior rectus, and, moreover, the 
 latter is then at its maximum as an elevator. Hence, to determine 
 the maximum elevating power of this muscle, we have only to 
 measure the range of excursion upwards that the eye can make 
 when abducted to this extent. Similarly, the range of excursion 
 downwards, when the eye is abducted 30°, measures the maximum 
 depressing power of the inferior rectus. Making use of the results 
 
 *Certainly the value of 20° found for the range of upward excur- 
 sion by Hering (cited in Gi^aefe-Saemisch) seems excessively small. 
 It is not unlikely that here there was a pathological condition 
 present, such as an insufficiency of one or both elevators — a phe- 
 nomenon not infi-equent. 
 
14 NEW CLASSIFICATION OF MOTOK ANOMALIES. 
 
 already talnilated,* we fiud for the maxinnim elevating power of the 
 supevinr rectus a value of 'S0°, and for the ?h«.'J?h«?» depressing poioer of 
 the inferior rectus, a nit-an value of 3r)'^-40'^. 
 
 The maximum elevating power of the inferior oblique and the 
 maximum depressing power of the superior oblique, are not so 
 readily determined, as the eye can hardly be so far abducted as to 
 enable these muscles to work to the greatest advantage, and at 
 The same time do away altogether with the vertical action of the 
 superior and inferior recti. It would appear, however, that the 
 maxinuim vertical effect exerted by the oblinues, does not differ materially 
 from that exerted by the straight muscles; only the effect of the latter in 
 the positions ordinarily assumed by the eye is rather more pronounced. 
 
 The maximum rotating effect of the superior rectus upon the ver- 
 tical meridian (torsion-effect, swivel-movement) will be ascertained 
 by determining the amount of deflection of the vertical meridian 
 Avheu the eye is directed far up and in. In this situation the ver- 
 tical meridian is not acted upon by the other muscles capable of 
 
 Fig. 1. 
 
 rotating it, so that the total rotation it undergoes must l)e ascril)ed 
 to the action of the superior rectus. So, too, the rotating power of 
 the inferior oblique, the supei-ior oblique, and the inferior rectus 
 is measured by the amount of tilting of the vertical meridian when 
 the eye is directed up and out, down and out, and down and in. 
 respectively. 
 
 The adducting effect of the superior and inferior recti and the 
 abducting effect of the obliques are not determinable directly in 
 the normal eye, since these actions ;ilw;iys occur as reinforcements 
 of the adducting and abducting actions of tlie interual and external 
 recti. 
 
 •■This can be accomplished by a simple calculation, based upon the 
 principles of spluM-ical trigonometry. 'J'luis if AB represents the 
 patli of tlie visual line in passing from the primary position obhipiely 
 up and out, BC (or a) will l)e tlie elevation and AC (or b) tlie outward 
 excursion or aliduction of the eye. Then Sin. a ::= Sin. A. Sin. c and 
 Sin. b = cot A. tan. a. Here c = the range of excursion up and out as 
 given by our table {— about 45'^), a = ;{0, and b = 3G^. 
 
XKW CLASSIFICATION OF MOTOK AXOMAI-IES. 15 
 
 For the same reason, the total adduction or abduction that the 
 eye is capal)le of is not a precise measure of the maximum poicer 
 of the erternal and internal recti, since the hitter are to a certain 
 extent, assisted in their action by the vertical muscles, and partic- 
 ularly so when the eye is already carried pretty far out or in. It 
 is probable, however, from observations in'cases of paralysis, that 
 the lateral action of the vertical muscles does not amount to more 
 tliau 4" or 5° at most, so that the abducting poirer of the e.'-ternns may be 
 stated as 40*-"-45o, and the adducting power of theinternus as about 50". 
 
 Passing now to the third group of fttnctions under considera- 
 tion, namely the character and relations of the movements p er- 
 formed by the two eyes when working together we arc struck by 
 the fact that, with unimportant exceptions,''' these movements are 
 limited to those subserving binocular fixation. 
 
 Thus, in order to produce the binocular fixation of distant ob- 
 jects, the visual lines must be parallel. In harmony with this 
 fact, we find that there is a whole series of movements — associ- 
 ated parallel inovements — in which the visual line of one eye is 
 kept strictly parallel with that of the other; and, moreover, the 
 vertical meridians of the two cornae also remain parallel, no mat 
 ter how the eye is directed. 
 
 A second class of movements — iiiovcmeiits of convergence — 
 adapt the eyes for the binocular fixation of near objects. 
 
 A third sort of movement is that of divergence in the horizon- 
 tal plane, causing the eyes to pass from the consideration of a near 
 object to that of one more i emote. In doing this, this movement, 
 like the preceding, svtbserves binocular fixation; but it may 
 to a certain limited extent, also antagonize the latter by carr}-ing 
 the eyes still further, i. e., from a position of parallelism to one of 
 actual divergence. 
 
 Another kind of movement, of very limited extent, is that of 
 divergence in a vertical plane^ produced by the elevation of 
 one visual line and the depression of the other. This move- 
 ment, called sursumvergence (or deorsumvergence) is denoted 
 as right or left, according as the right or left visual line is 
 higher (or lower). 
 
 *The exceptions are very clearly described by Helmholtz (Phys. 
 Optik, 2d Ed., pp. 631, et seq.) He seems to me, however, to have 
 laid too much stress upon the ability of the eye to make exceptional 
 movements of this sort; the fact being that such movements ar.- 
 extremely limited and, beyond a certain point, cannot be increased 
 by practice. It seems, therefore, that in spite of his statement 
 to the contrary, there is some anatomical basis for the inability of 
 the eye to make unaccustomed movements and tliat it is not simply 
 a question of training. 
 
16 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 A fifth class of iiioveinents comprise those in which the vertical 
 niv)-idia7is of the two cornccc are so rotated as to be no longer 
 parallel. Such a rotation occurs normally in positions of marked 
 convergence, the vertical meridians then diverging at their up- 
 per extremities, and the amount of divergence increasing as the 
 eyes are elevated (Meissner, Le Conte). But, apart from this 
 physiological torsion-movement, a divergent or convergent ro- 
 tation of the vertical meridians may be produced in the normal 
 eye and demonstrated by suitable apparatus (Helmholtz). 
 
 The Associated Parallel Movements of the two eves with the 
 muscles concerned in their production are shown in the follow- 
 ing tables: 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 17 
 
 Both I 
 Eyes 
 Movetoi R. Eye 
 
 Muscles con- 
 cerned 
 
 Move eyes 
 laterally* 
 
 Move eyes 
 vertically* 
 
 meridians ' " 
 
 ofcorneae. 
 
 1 
 
 Right j 
 
 External Internal 
 
 To R. 
 
 ! 
 
 No action 
 
 No action 
 
 R eye carried 
 
 Rectus Rectus 
 
 
 
 
 toRby the ex- 
 
 (Dex- 
 
 
 
 
 
 ternal rectus 
 
 1 
 
 
 
 
 assisted by the 
 
 sion.) 
 
 Synergists 
 
 
 
 [ToL a&. 
 
 obliques: 
 
 L eye carried 
 to R by intern- 
 
 
 Superior Inferior 1 
 
 To R, ac- 
 
 Down actions 
 
 al rectus assist- 
 
 
 Oblique Rectus ' 
 
 tion in- 
 
 1 equal 
 
 O 
 
 ed by the supe- 
 
 
 
 creasing 
 
 andop- 
 
 rior and infer- 
 
 
 Inferior Superior 
 
 the more 
 
 i posite 
 
 S3 
 
 ior recti. The 
 
 
 Oblique Rectus J 
 
 eyes are 
 
 [Up 
 
 [•ToR ^-c 
 
 other muscles 
 
 
 
 carried 
 
 
 J C £. 
 
 act to steady 
 
 
 1 
 
 UoR 
 
 
 
 the eyes and 
 keep them in 
 
 
 Opponents. 
 
 
 
 
 the horizontal 
 plane. Vertical 
 
 
 Superior Inferior! 
 
 ■ [To L] ac- 
 
 [UpJ 
 
 Actions 
 
 [ToLlgS 
 
 meridiansboth 
 
 
 Rectus Oblique i 
 
 tion sli't 
 
 
 equal 
 
 S"? 
 
 remain verti- 
 
 
 I 
 
 & dimin- 
 
 
 and op- 
 
 '■2 '^ 
 
 cal. 
 
 
 Inferior Superior 
 
 ishing as 
 
 
 posite 
 
 
 
 Rectus Oblique J 
 
 1 eyes are 
 1 carried 
 
 [Down 
 
 
 n 
 
 [Tor ^-I 
 
 
 
 i 
 
 I to R. 
 
 
 
 
 n p 
 
 
 Left 
 
 Internal External 
 
 ToL- 
 
 No action. No action 
 
 R. eye carried 
 
 
 Rectus Rectus ' 
 
 
 
 to L. by the in- 
 
 (Sinis- 
 
 
 
 
 ternal rectus, 
 
 
 
 
 1 assisted by the 
 
 sion.) 
 
 Synergists. \ 
 
 
 ToL 
 action 
 
 ~1 ac- 
 
 ] g ^ 1 superior and 
 c.-.' inferior recti: 
 
 
 Superior Inferior 
 
 
 increas 
 
 [ U p 1 tions [ To L 1 o § ' L. eye carried 
 
 
 Rectus Oblique 
 
 
 es the 
 more 
 
 .equal ^§ » : to R. by theex- 
 
 and go ternal rectus, 
 
 [Down oppo-;[ToR ^-c assi.sted by the 
 
 J site. ! h^' obliques. The 
 
 1 t other muscles 
 
 
 Inferior Superior 
 Rectus Oblique 
 
 
 eyes 
 are car- 
 ried to 
 
 
 
 
 T.. 
 
 
 act to steady 
 
 
 
 
 
 1 the eyes and 
 
 
 Opponents. 
 
 
 [To R] 
 
 "1 ac- 
 
 keep them in 
 1 » » 1 the horizontal 
 
 
 Superior Inferior 
 Oblique Rectus 
 
 
 B^ 
 
 [Down tionsi[ToL §.» plane Vertical 
 
 equall o o meridians re- 
 
 f and 1 § S i maiii vertical 
 
 
 Inferior Superior 
 
 
 
 |Up] oppo-[ToR o^ 
 
 
 
 Oblique Rectus 
 
 
 J site. J || 
 
 
 
 
 
 
 
 
 1 
 
 [ToL]|§ 
 
 i ;[ToLl 
 
 S^L ,u 
 
 Up 
 
 1 Superior Inferior 
 
 Up 
 
 
 acr.lBoth eyes car- 
 
 
 Rectus Oblique 
 
 
 
 o g I ried vertically 
 
 [Sur- 
 
 
 1 
 
 
 t) S up by combiu- 
 
 suni- 
 
 
 1.1 
 
 
 
 ■grt ied action of su- 
 
 ver- 
 
 
 
 
 ii.c perior rectus 
 
 sion.] 
 
 1 Inferior Superior 
 Oblique Rectus 
 
 [ToR]i''£ 
 
 Up 
 
 [ToR 
 
 g^£,l and inferior 
 oblique. Exter- 
 nal and inter- 
 
 
 Si/nergists. 
 
 >» 
 
 
 i ual recti act to 
 steady eye and 
 
 
 External Internal 
 Rectus Rectus 
 
 [ToR] 
 
 
 No action 
 
 No action keep it in verti- 
 cal plane. Ver- 
 tical meridians 
 
 
 1 Internal External 
 
 
 " 
 
 remain verti- 
 
 
 Rectus Rectus 
 
 [To L] ^•g 
 
 ... 
 
 *Portions enclosed 
 ized. 
 
 brackets indicate movements which are completely neutral 
 
18 
 
 XEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 Both Muscles coucerued 
 
 Eyes 
 
 Move R Eye • L Eye 
 
 and 
 to R. 
 
 and to 
 L. 
 
 Move eyes 
 
 t-ertically 
 
 Rotate up- 
 per ends of 
 
 vertical 
 meridians 
 of corneae 
 
 Resultant 
 effects up- 
 on eyes 
 
 Superior Inferior 
 Rectus Oblique 
 
 Inferior Superior 
 Obliciuc Rectus 
 
 Syiierglsti. 
 
 External Internal 
 Rectus Rectus 
 
 [To L.] Up. Action 
 Action marked and 
 
 slight and increasing as 
 decreasing eyes are ear- 
 as eyes are ried to R. 
 carried to R 
 I 
 To R. Up. Action 
 
 Actions slight and de 
 marked & creasing as 
 increasing | eyes are ear- 
 as eyes are iried to R. 
 carried to R 
 
 [To I J Ac- 
 tion slight 
 
 and de- 
 creasing as 
 eyes are 
 carried to R 
 
 To R. 
 
 Action 
 marked & 
 increasing 
 as eyes are 
 carried to R 
 No action. 
 
 R. eye carried 
 up by superior 
 rectus; L. by in- 
 ferior oblique. 
 R. eye carried 
 to R. by exter- 
 nal rectus as- 
 sisted (espec- 
 iallyin extreme 
 abduction ) by 
 inferior obli- 
 que: L. eye car- 
 ried to R by in- 
 ternal rectus 
 assisted by su- 
 perior rectus. 
 Both vertical 
 meridians tilt- 
 ed to R. 
 
 Inferior Superior 
 Oblique Rectus 
 
 Superior Inferior 
 Rectus Oblique 
 
 Sinierffiutt^ 
 
 [ToR] Ac- Up. Action 
 jtion slight marked and in- 
 & decreas- creasing as 
 ling as eyes eyes are car- 
 are carried ried to R 
 to L. 
 I I 
 
 To L. Up. Action 
 
 I Action I slight and de- 
 marked & creasing as 
 increasing eyes are ear- 
 as eyes are | ried to L. 
 carried toL 
 
 [To Rl Ac- 
 tion slight 
 & decreas- 
 ing as eyes 
 are carried 
 to I,. ! 
 
 To L Ac- 
 tion mark- 
 ed and in- 
 creasing as 
 eyes are 
 carried to 
 
 Internal External To L. 
 
 Rectus Rectus 
 
 R. eye carried 
 up mainly by 
 inferior ob- 
 lique, I, eye by 
 superior rec- 
 tus: R eye car- 
 ried to L by in- 
 ternal rectus 
 assisted by 
 superior rec- 
 tus. L eye car- 
 ried to L by ex- 
 ternal rectus 
 assisted by in- 
 ferior oblique. 
 Vertical meri- 
 dians both ro- 
 tated to L 
 
 Down 
 
 (Deor- 
 sum 
 ver- 
 sion) 
 
 Inferior Superior 
 Rectus Oblique 
 
 Superior Inferior 
 Oblique Rectus 
 
 Si/nerfflsts. 
 
 External Internal 
 Rectus Rectus 
 
 Internal External 
 Rectus Rectus 
 
 [ToR 
 
 [ToRl 9?", 
 
 [ToLhS 
 
 [Tol 
 
 [To R I R?^ Both eyes car- 
 o a! ried vertically 
 I 2 S ! down by com- 
 bined action of 
 inferior rectus 
 and superior 
 oblique. Ex- 
 ternal and 
 internal recti 
 act to steady 
 I eyes and keep 
 hen 
 
 ■ ertical plane. 
 Vertical mer- 
 idians remain 
 vertical. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 19 
 
 Both 
 Elyes 
 Move 
 
 Muscles concerned 
 R Eye L Eye 
 
 Move eycf 
 laterally 
 
 Down 
 and to 
 R. 
 
 Inferior Superior 
 Rectus Oblique 
 
 Superior 
 Oblique 
 
 [To L.] Ac 
 tiou slight 
 & decreas 
 
 Inferior To R. Ac- 
 Rectus tions 
 
 marked & 
 increasing 
 
 Move eyes 
 vertically 
 
 Rotate up- 
 per ends of 
 
 vertical 
 meridians 
 of cornese 
 
 Si/nergists. 
 
 External Internal 
 Rectus Rectus 
 
 Down. Action 
 marked and in- 
 creasing as 
 eyes are car- 
 ried to R 
 
 Down. Actions 
 slight and de- 
 creasing as 
 eyes are ear- 
 
 as eyes are ried to R. 
 carried to 
 
 [To R.] 
 Action 
 slight and 
 decreasing 
 as eyes are 
 turned to 
 R. 
 
 ToL. 
 Action 
 marked 
 and in- 
 creasing as 
 eyes are 
 carried to 
 R. 
 
 No action. 
 
 Resultant 
 effects up- 
 on eyes 
 
 R. eye carried 
 down mainly 
 by inferior 
 rectus, R. eye 
 by superior ob- 
 lique, R. eye 
 carried to R by 
 external rec- 
 tus assisted by 
 superior ob- 
 lique, L- by 
 internal rectus 
 assisted by 
 inferior rectus. 
 Both vertical 
 meridians ro- 
 tated to L. 
 
 Down 
 and to 
 
 Superior Inferior 
 Oblique Rectus 
 
 Inferior Superior 
 Rectus Oblique 
 
 Synergists. 
 
 Internal External 
 Rectus Rectus 
 
 [To R.] Ac- 
 tion slight 
 and de- 
 1 creasing as 
 jeyes are 
 carried to 
 L. 
 
 ;To L. a 
 Jtion 
 marked 
 and in- 
 
 Down. Ac- 
 tion malted 
 and increasing 
 as eyes are 
 carried to L. 
 
 [ToL.] Ac- 
 tion slight 
 and de- 
 creasing as 
 eyes are 
 carried to 
 L. 
 
 creasing as ried to L. 
 eyes are i 
 carried to 
 
 ,L. I 
 
 Down. Action To R 
 slight and de 
 creasing as 
 eyes are 
 
 To L. 
 
 No action. 
 
 Ac- 
 
 tion 
 marked 
 and in- 
 creasing as 
 eyes are 
 carried to 
 L. 
 
 No action. 
 
 R. eye carried 
 down mainly 
 by superior 
 oblique, L. by 
 inferior rectus. 
 R. eye carried 
 toL.bj' internal 
 rectus assisted 
 by inferior 
 rectus; L. 
 eye carried 
 to L. by exter- 
 nal rectus as- 
 sisted b}' supe- 
 rior oblique. 
 Both vertical 
 meridians ro- 
 tated to R. 
 
 An inspection of the tables just given will show that in all 
 parallel movements of the eyes each muscle acting upon the 
 right eye is associated with a muscle which acts upon the left 
 eye in a precisely similar manner, and to a precisely equal extent. 
 Such a pair of muscles, one in each eye, are termed associated 
 antagonists (A Graefe). 
 
 Thus the superior rectus of one eye and the inferior oblique of the 
 other are associated antag-onists. since in all positions that the two 
 eyes may assume, these muscles move their respective eyes to the 
 same extent and in the same direction, so that if they acted alone 
 they would always keep both visual lines and both vertical meri- 
 dians parallel. The associated antagonists and their action may be 
 summarized as follows: 
 
20 
 
 NKW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 ASSOCIATED ANTAGONISTS. 
 
 Muscle. 
 R. eye. 
 
 Moves eye 
 
 laterally 
 
 to 
 
 Moves eye 
 1 Vertically 
 
 i 
 
 Vertical 
 action in- 
 creasing & 
 Rotates up- latent ac- 
 per end of tiondimin- 
 vertical ishing as 
 meridian eyes are 
 cornea | turned to 
 
 ASSOCIATED 
 
 ANTAGONIST. 
 
 L eye 
 
 External Rectus 
 
 R 
 
 No action 
 
 1 
 No action ! 
 
 Internal Rectus 
 
 Internal Rectus 
 
 L 
 
 No action 
 
 No action 
 
 External Rectus 
 
 Superior Rectus 
 
 L 
 
 ; Up 
 
 h R 
 
 Inferior Oblique 
 
 Inferior Rectus 
 
 L 
 
 Down 
 
 R R 
 
 Superior Oblique 
 
 Superior Oblique 
 
 R 
 
 Down 
 
 L I. 
 
 Inferior Rectus 
 
 Inferior Oblique 
 
 R 
 
 1 - 
 
 R L 
 
 Superior Rectus 
 
 The determination of the ra??/fe of excursiojt in associated 
 ■parallel movements comprises the solution of two distinct prob- 
 lems, namely, the determination of the field of binocular single 
 vision and the determination of the field of binocular fixation. 
 We delimit the Jield of binocular fixation by ascertaining for 
 each direction of the gaze the point at which either one of the 
 eyes fails to follow an object moving before the two. This 
 can be done very conveniently with the double dot used for 
 testing the monocular field of fixation, since the moment when 
 either eye fails to follow the dots or when either eye fails to 
 keep up with the other in following them, is rendered evident 
 by a blurring of the image causing the two dots to run into one. 
 
 Heriug:, who used a different method (with after-images), found 
 the binocular field to be of quite small extent, being considerably 
 smaller than the portion common to the tAvo monocular lields. 
 
 It seems likely, however, that his tests in this case, as in the ease 
 of the monocular Held, were made upon a not altogether normal sub- 
 ject. My own researches, altliough few, to be sure, were made upon 
 quite normal individuals. They gave the following results:* 
 
 MOVEMENTS OF BOTH EYP^S. 
 
 Down and Down and 
 risht. left. 
 
 TT„ Up and Up and tj:„v,. 
 Up- right. left. K'^^^- 
 
 Left. Down. 
 
 Case I.... 
 
 .. 38 
 
 fi'i 
 
 4.5 
 
 58 
 
 52 
 
 Case 11... 
 
 .. 50 
 
 r)2 
 
 53 
 
 06 
 
 n'.t 
 
 The delimitation of the field of binocular single vision is ef- 
 fected by noting in any particular direction Of the gaze the point 
 at which one eye can no longer keep pace with the other, as 
 evidenced by the development of an insuperable diplopia. 
 
 The field defined by joining all such points is not necessarily coin- 
 cident with the field of binocular fixation, since it is quite conceiv- 
 able that the two eyes folloAving a moving object might fail to fix 
 
 lOxaminatidu made for near ]><)ints. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 21 
 
 it, but might yet both lag behind to au equal extent, so that the 
 two images, although not formed upon the macula;, would still be 
 formed upon corresponding points. In this case, binocular single 
 vision would still be present, although binocular fixation would no 
 longer exist. 
 
 A point upon which some stress has been laid is that this method 
 of delimiting the held of fixation gives uncertain results, since, as 
 is alleged, many people fail to recognize diplopia in eccentric posi- 
 tions of the gaze. It is claimed, in other words, that the normal 
 field of binocular single vision is quite small, and that diplopia 
 occurs normally in looking far up, far to the right, etc., but that 
 its existence is not suspected, because the subject under examination 
 either fails to notice or actually suppresses one image. My own 
 experiments, however, lead me to negative this idea completely. If 
 we employ a candle for our test-object, and place a red glass before 
 oue eye of the individual examined, the presence of binocular single vision 
 will be shown by the fact that the candle-flame appears pinkish or, more 
 commonly yellow with a reddish border. Manifest diplopia will be shown 
 by the presence of two flames, one red and the other yellow, and dip- 
 lopia with the snppression of either image by the presence of one flame, 
 either pure red or pure yellow. The differences presented are marked 
 and readily appreciated by an intelligent patient when once they have 
 been pointed out to him. 
 
 Testing in this way a large number of people with apparently 
 normal eyes, I have uniformly found that the field of binocular 
 single vision extends not less than 40° in atzy given direction 
 and usually extends up to 50° or more. Indeed, most persons 
 still get true binocular single vision, even when the eyes are 
 carried to the extreme limit of their excursion, the field of bin- 
 ocular single vision being larger than either monocular field 
 of fixation taken separately. This is but another instance of 
 the law that the movements of the eyes, however extensive or 
 however limited in themselves, are always under normal con- 
 ditions modified in such a way as to best subserve binocular 
 fixation and binocular single vision. Thus, as the experiments 
 just adduced seem to show, it appears that, no matter what the 
 maximum range of excursion of each eye separately is, the ex- 
 cursion of both together, effected by the co-ordinating action 
 of the association-centres, is such that one eye keeps pace with 
 the other, going neither faster nor slower, and that each stops 
 moving when the other does. Hence, however far the object 
 looked at may be carried in any given direction, no diplopia 
 occurs, or, if it does, it is transient and superable.* 
 
 *These statements presuppose (1) that the visual lines are not 
 far from parallel, i. e., the test-object should not be less than :: 
 feet from the eyes: and (2) the person examined should endeavor all 
 the time to follow the o^bject. i. e., must not look beyond it. In the 
 latter case, of course, the test-object will seem to him double. Such 
 diplopia is. however, usually at once superable by voluntary effort. 
 
22 NEW CLASSIFICATION' OF MOTOK ANOMALIES, 
 
 Each of the main associated parallel movements turning 
 (dextroversion, or the turning of both eyes to the right, 
 sinistroversion, or the turning of both eyes to the left, sur- 
 sumversion, or parallel movement up, and deorsumversion, or 
 parallel movement down) is apparently fresided over by a dis- 
 tinct nucleus (association centre). The precise location of these 
 centres has not been satisfactorily determined, but the evidence of 
 their existence from pathology is very strong, lesions in which 
 dextroversion and sinistroversion alone are afifected being not in- 
 frequent, and isolated involvement of sursumversion also hav- 
 ing been recorded. These facts will be referred to later on. 
 
 Movements of convergence may be regarded as associated 
 parallel movements to which a simultaneous contraction of 
 both interni has been superadded. Thus in looking at a near 
 object situated up and to the right there is a movement of sur- 
 sumversion and dextroversion combined with a contraction of 
 both interni, which neutralizes in part the right-hand move- 
 ment of the right eye, and reinforces the right-hand movement 
 of the left eye. 
 
 This double contraction of tlie interni is presided over by a 
 special centre (convergence centre)^ distinct from the association 
 centres for parallel movements. 
 
 Convergence, when marked, modifies somewhat the effect of the 
 other muscles that are acting with tlie interni. Thus when the gaze 
 is directed at a near object in the median line, the superior rectus 
 of one eye and tlie inferior oblique of the other no longer act as 
 associated antagonists, the fonner serving mainly to adduct, and 
 the latter to elevate the eye. In this case, in fact, the superior and 
 inferior obliques in each eye neutralize each other completely, and 
 the two superior and two inferior recti act as synergists to the two 
 interni, all adducting the eye. Again, when the gaze is directed 
 at a. very near object, situated upward and to the right, the right 
 superior rectus, since the right eye is not pointed as far to tlie 
 right as the left one is, will not be working as an elevator at quite 
 the same mechanical advantage as does the left inferior oblique. 
 Theoretically, therefore, the right eye will lag somewhat below thf 
 left. Practically, I have not observed this to occur, although it 
 does seem to me that the field of binocular single vision is smaller 
 for convergent than for parallel movements. 
 
 The tnaximtini power of convergence is obviously represented 
 either by the angle formed by the two visual lines when both 
 eyes are turned in to their utmost extent, or by the distance from 
 the eyes of the nearest possible point upon which they can be 
 converged. This point is called the fusion near-point, or. better 
 the near-point of convergence (Pc.) Bonders in a boy of lo 
 found the maxinuim angle of convergence to be 70*^, which, 
 
NEW CLASSIFICATION OK MOTOlt ANOMALIES. 23 
 
 with an interocular distar.ce of 00 mm., would signify a near- 
 point of convergence situated 52 mm. from the centre of rotation 
 of. either eye and 42 mm. in front of the hne joining the centres 
 of both eyes , or about 1^" from the cornea and ^" in front of 
 the bridge of the nose. Some can converge to even a greater 
 extent. Prof. Le Conte, for example, who had acquired ex- 
 traordinary facility in the use of his eyes, had a convergence- 
 angle of nearly 90=*. Schuurmann, on the contrary, found a 
 maximum convergence-angle of only 43°, which would corre- 
 spond to a convergence near-point situated about 25" from the 
 corneie and 22" in front of the bridge of the nose ; and v. Graefe 
 gives to the convergence-angle a value of 00° corresponding to 
 a distance of 2" from the eye, and 1^-'' from the bridge of the 
 nose. My own experience leads me to regard Schuurmann's 
 figures as expressing most nearly the results found in the general 
 average of cases, the convergence near-point in the majority 
 of normal persons that I have examined being situated at about 
 1" in front of the nose. A distance of \\"-\L" may, in fact, be 
 regarded as the normal for adults. Children often have a greater 
 power of convergence, and in them the distance may not ex- 
 ceed V . A distance of less than 1" denotes excessive, and one 
 of over 2^'' deficient convergence-power. 
 
 Another method of determining the power of convergence is 
 by ascertaming the- sfreno-//i of prism, which can be overcome 
 by the eyes when placed before the latter with its base out or 
 towards the temple. 
 
 This method is analogous to that employed by Donders for de- 
 termining the positive portion of the range of accommodation. TIi3 
 strength of prism overcome, in fact, represents the amount of 
 residual convergence* that the subject under examination can ex- 
 ercise when his eyes are adjusted for the distance of the test-ob- 
 ject employed, just as the strength of the concave glass that he 
 can overcome represents tlie amount of his residual accommodaiion 
 under the same conditions. The amount of this residual conver- 
 gence naturally varies with the distance of the test-object, decreas- 
 ing as the latter is brought nearer. It also varies considerably for 
 the same distance in different individuals, until the latter have by 
 training learned to do what at the outset is quite difficult for them, 
 namely, to look at a distant object and at the same time direct 
 their eyes as if it were much nearer than it really is. When this art 
 has been learned, it will be found that. 
 
 Normal subjects will for test-objects at a, distance of twenty 
 feet overcome prisms of 00°-70° refracting angle (equivalent to 
 a convergence of 40°-.50°), so that the maximum convergence 
 produced in this way equals that produced in the natural fashion, 
 i. e., by looking at a very near object. 
 
 ♦Often improperly called the adduction. 
 

 
 
 Cor 
 
 responding amount 
 accommodation for 
 
 Actual amount of 
 
 con- 
 
 
 of 
 
 vcrgence produced by 
 
 Accommodation ex- 
 
 a natural convei-gence 
 
 overcoHiingtliepi 
 
 risiu. 
 
 erted. 
 
 of the same degree. 
 
 4.3" 
 
 
 0.25 
 
 
 1.25 
 
 6.5^ 
 
 
 0.50 
 
 
 2.00 
 
 11.00^ 
 
 
 1.50 
 
 
 3.25 
 
 15.5'^ 
 
 
 2.50 
 
 
 4.50 
 
 19.3° 
 
 
 5.00 
 
 
 5.50 
 
 24 XEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 Convergence thus produced by prisms is at first associated 
 with an accoiiinwdative effort similar to, but less than that ac- 
 companying a natural convergence of the same degree. Thus 
 two cases that I examined showed the following amount of ac- 
 commodation : 
 
 Ctiise 1 
 Case 2 . 
 
 By continual practice, however, the patient may learn to relax 
 the accommodation while maintaining the convergence, and in this 
 way prisms of 20° or 30°, base out, may be overcome without the 
 accommodation being used at all. I have met with an extreme in- 
 stance of this sort in which the patient could, without making any 
 accommodative effort whatever, overcome prisms representing a 
 convergeuce-angle of nearly 40°. 
 
 Divergence, or the simultaneous lateral separation of the 
 visual lines, is a process which ordinarily subserves binocular 
 fixation, being used when the eyes fix in succession objects more 
 and more remote. The process may, however, be performed 
 to excess, so that the visual lines diverge from the object of fixa- 
 tion, as when the homonymous diplopia caused by a prism 
 placed base in before the eye is overcome, or, on the other hand, 
 an involuntary or voluntary crossed diplopia is produced by 
 turning the eyes outward. 
 
 Divergence of the sort last mentioned, i. e., that giving rise 
 to a crossed diplopia, varies greatly in amount, and, although re- 
 garded as normal by those experimenters who have acquired a 
 peculiar facility in producing it, is probably to be classed among 
 the abnormalities. At all events, there are not many in whom the 
 phenomenon is habitual, or who can produce it at will, and when 
 present, it is generally associated with lack of muscular balance, 
 and other evidences of a pathological state. 
 
 On the other hand, a divergence produced in the act of over- 
 coming a prism placed, base in, before the eyes, is an entirely 
 normal phenomenon of very definite character. Its maximum 
 amount naturally varies with the distance of the object of fixa- 
 tion, increasing as the latter approaches the eye. The strength, 
 in fact, of the prism, base in, that the eyes can overcome when 
 regarding an object at any given distance, represents the amount 
 by which the eyes, when converged upon the object and accom- 
 morlatod for tlic latter, can diverge; jxist as the strength of the 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 20 
 
 convex glass that can be overcome in looking at the object rep- 
 resents the negative portion of the range of accommodation for 
 the same distance. For distance, i. e.. when the visual lines are 
 parallel, the divergence* amounts quite regularly to from 3° to 
 5° (= divergence produced in overcoming a prism of 6° to 10°) ; 
 and variations above or below these limits must be regarded as 
 distinctly pathological. 
 
 As to the true nature ofdivergt^nce, i. e. ; whether it consists in 
 an active muscular contraction as in the case of convergence, or 
 whether it is simply a relaxation of the interni, allowing the eyes 
 to return to a position of rest, there has been much difference of 
 opinion. 
 
 Those who adopt the hitter view assume that the natural position 
 of the eyes, i. e., that in which all the muscles are fully relaxed, is 
 one of slight divergence, parallelism itself requiring" a certain tonic 
 and constant contraction of the interni for its maintenance (Hansen 
 Grut). Some liave even thought that the position of complete re- 
 laxation is that in which each visual axis coincides with the axis 
 of the orbit — a state of things implying a divergence of 25°-30° (l.e 
 Conte). Those who thus think, however, appear to be misled in 
 reg'arding as natural a condition which is abnormal, not to say patho- 
 logical. Schweigger lias argued strenuously against Hansen Grut's 
 theory and especially to his application of it as explaining the 
 nature of divergent squint, and Sehueller also has adduced a variety 
 of arguments, which, however, are not very convincing, to prove 
 that the function of divergence is an active process. For my own 
 part, I believe that in the majority of cases the poisition of perfect 
 physiological rest is not one of divergence and that, consequently, 
 the lateral separation of the visual lines must be regarded as, in 
 part at least, an active process due to simultaneous contraction of 
 the externi. One argument in favor of this is that many people, 
 when we test their divergence with prisms, experience a marked 
 sense of strain analogous to that felt in overcoming prisms by con- 
 verg'ing the eyes. The latter is certainly an active process, and the 
 former, therefore, in these cases at least, would seem to be one also. 
 Patients, to be save, who can diverge at will so as to produce 
 crossed diplopia, often assure us that they do so by "relaxing" tlie 
 eyes; but several o'bservations have convinced me that this relaxa- 
 tion is really a muscular contraction. f 
 
 Perhaps the strongest argument in favor of the idea that diver- 
 gence is a passive and not an active process is that, in the great 
 majority of cases at least, the diverging power, as measured h>i 
 the ability to overcome prisms, base in, can not be increased at all 
 beyond the initial amotmt, shown by the subject experimented upon 
 If. for exatnii>le. in our first ti'ial of a patient, at the maximum prism. 
 base in, that he can overcome is one of 8°, we s'hall generally find 
 
 ♦Usually but improperly called the abduction. 
 
 fA similar instance in which an undoubted muscular contraction 
 was described by the patient as a "relaxation" was one that I met 
 with, in which an homonymous diplopia of 15° (prism) was produced 
 at will. Here, of course, a condition of convergence was present, 
 which could only have been brought about by an active contraction 
 of the interni. 
 
2G NEW CLASSIFICATION OF MOTOH ANOMALIES. 
 
 that we can not get him beyoud this ixjiut by aiiy amouut of sub- 
 sequent traiuiuy. If divergence were a process of active muscuku- 
 contraction it would seem as if it ouglit to be su8ceptil)le of being 
 increased by exercise. 
 
 But whatever the nature of divergence, whether active or pas- 
 sive, it is certainly a distinct function of the eyes, and probably 
 regulated by a distinct nervous mechanism. The evidence af- 
 f(^rdcd by patliology, at all events, point very stronglv in this 
 direction. 
 
 Separation of the visual lines in a vertical plane (sursumduc- 
 tlon, or, inore properly, sursumvergence) is a movement which 
 all normal eyes can perform. It is, however, very limited in 
 amount, not normally exceeding 1° or 1|° {= the divergence 
 produced by a prism of 2° or 3°). It is evidently an active pro- 
 cess associated with a sense of considerable strain, and appears 
 susceptible of being increased by exercise, particularly in those 
 that have a natural or acquired vertical deviation (hyperphoria). 
 
 The power of producing convergence or divergence of the 
 vertical meridiaas of the two eyes, the visual lines remaining 
 parallel, is a subject about which very little is known. Even the 
 experiments of Helmholtz, which seem to prove its existence, 
 have been called into question by some, althotigh probably with- 
 out sufficient reason. 
 
 Appendix. The analysis of the complicated problems involved in 
 the study of the mnvenients of the eyes may be facilitated by re- 
 ference to the diagram (Fig. 2), which represents the field of fixation 
 of a normal eye having a rather extensive power of motion. 
 
 PROJECTION OF THE FIELD OF FIXATION AND OF THE 
 
 FIELD OF ACTION OF EACH OF THE 
 
 OCULAR MUSCLES. 
 
 C, projection of extremity of line of sight (point of fixation), when 
 eye is in primary position; D, E, O, projection of same when eye 
 IS abducted 18°. 30°, and 50°, respectively; B, A, P, projection when 
 eye is adducted 20°, 50°, and G0°, respectively. The distance CO 
 represents the maximum degree of excursion of the eye outward 
 Most of this movement is effective by the e.rtenml m7»s, but a cerlain 
 portion especially towards the outer eud of the excursion is accomplished 
 by the united action of the two obliques (see ivfra). The distance CT 
 represents the niaxinuiiii range of excursion of the eye inward This 
 inward movement is effected mainly bv the i»(ernal rectus, assisted 
 especially towards the eud of the excursion by the superior and inferior 
 recti (see infra). 
 
 The black lines AA,, 15B,, C(\. 1)D,. EEi, repre.sent the amount 
 and direction of the movement produced by the superior rectus when 
 the eye is respectively addncled r>0^' (A); adducted 20« (H); j,, the 
 primary position (O) ; abducted ]S-' (D); and abducted M0« (K) The 
 red lines AAt, BH,,. CC,,. 1)1).,, EE,,. represent the amount and di- 
 rection of the nioveiiient eflfected by the inferior oblii/ue. and the 
 (lotted lines AA,j, BB.i, CCa, DDg, EE3, tJie moveiuent effected by the in- 
 
NEW CLASSIFICATION OF MOTOR ANOMAI.ItS. 27 
 
 ferior oblique and the superior rectus acting together. Similarly, the 
 black lines AA4, IJB4, ('C4, 1)1)4, KK4 represent the lines of action of the 
 inferior rectus; AA5. BB5, CC5, DDs, EEs, those of the superior oblique; 
 and AAe, BBg, CCe, DDq, EEe, those of the two latter muscles combined. 
 The heavy black lines AiBiCiDiKi and A4B4C4D4E4 represent the limits of 
 the Jiekls of action of the superior and the inferior recti; and the heavy 
 red lines, A2B2C2D.2E..; and AftB^CsDsEs the limits of the tields of action of 
 the inferior and the superior obliques. The heavy dotted line AePAaBs 
 C3, etc., represents the limit of ihQ field of fixation. 
 
 It will be seen from the diagram how the vertical (elevating and 
 depressing) action of the superior and inferior recti increases, and 
 how the vertical action of the obliques decreases progressively as the 
 eye is carried from a position of marked adduction (A) to one of 
 moderate abduction (E). It will also be apparent how the lateral 
 action of each of these muscles diminishes as its vertical action in- 
 creases; so that the adductive power of the superior and inferior 
 recti shows a progressive diminution, and the abduetive power of 
 the two obliques a progressive increase as the eye passes from A 
 to E. That is, at A (i. e., when the eye is adducted 50°) the superior 
 ;ind inferior recti have no vertical action at all, but simply adduct 
 the eye through a comparatively large extent, while the two oWiques 
 liave no lateral action at all, but simply elevate and depress the 
 eye. 
 
 At E, on the other hand (when the eye is abducted 30°), the two 
 recti no longer act as adductors at all, but simply elevate and de- 
 press the eye; and the two obliques no longer exert any vertical 
 effect, but combine to carry the eye outwards, their abduetive action, 
 in fact, being here at its maximum. 
 
 At A the superior rectus and the inferior oblique acting together 
 to their full extent will cariT the eye up and noticeably inwards 
 to A3) ; since here the adductive action of the rectus is at its max- 
 imum and besides is not balanced by any opposing abduetive action 
 on the part of the oblique. Similarly at E the two muscles acting 
 together will carry the eye upwards and noticeably otttwards. In In- 
 tel-mediate positions, as at B and D, the lateral action of one muscle 
 will partially counteract that of the other, so that the net lateral 
 effect will be less. E. g., at B the adductive action of the superior 
 rectus is less than it was at A and moreover is now opposed by a 
 moderate abduetive action on the part of the inferior oblique, so 
 that the net adductive effect is but slight. The eye, therefore, here 
 is carried up by the inferior oblique, assisted somewhat by the 
 superior rectus, and is also carried slightly inwards (to B3). At D, 
 on the contrary, it is carried upwards mainly by the superior rectus, 
 assisted somewhat by the inferior oblique, and is also carried 
 slightly outwards (to D3), by the preponderating lateral (abduetive) 
 action of the latter muscle. At C (the primary position) the adduc- 
 tive action of the superior rectus apparently balances the abduetive 
 action of the inferior oblique, and hence the etfeot of the two ele- 
 vators acting together will be to carry the eye straight upwards. 
 
 In a similar way the inferior rectus and the superior oblique acting to- 
 gether will carry the eye down and in (AAe, BBe) , down and out (DDg, EEk) , 
 or straight down (CCe), according as the eye is already adducted, ab- 
 ducted, or in the primary position. 
 
 The superior or inferior rectus actina together with Just sufficient 
 force to neutralize each other's vertical action, will combime to ad- 
 duct the eye, the adducent effect being forcible at A ''=AAi4-AA4 or 
 AA7), and diminishing graduallv to E where it is zero. At E. there- 
 fore, i. e.. when the eve is abducted ."^O", the inferior and superior 
 
28 NEW CLASSIFICATION OV MOTOK ANOMALIES. 
 
 recti aetiugr together will pi-oduce no movemeut aud beiice in this 
 position are dii-ect antagonists. 
 
 Similarly the superior and inferior oblirjnes acting together neu- 
 tralizes each others' vertical action, but combine to abduct the eye. 
 The abducent effect is greatest at E (= EE2+EEo=KE8j, aud dimin- 
 ishes progressively to A, where it is zero. In tlie latter position, there- 
 fore, i. e., when the eye is abducted 50°, the two obliques, acting simply 
 to elevate and depress the eye respectively, are direct antagonists. 
 
 The four muscles, superior atid inferior recti and superior and in- 
 ferior oblii/nes acting together with ihe force required to neutralize 
 each other's vertical action, will produce a lateral efltect varying 
 with the amount by which the eye is already abducteil or adductcd. 
 Thus if the eye is already adducted 50° (to A), a position in which 
 the obliques exert no lateral action at all, the total effect of tlu' 
 four muscles will be to carry the eye quite a little distance further 
 inward (to At). If the eye is adducted only 'M^ (B), the resultant 
 action of the four muscles will be the difference between the adduc- 
 tive action of the two recti (BB7), and the less marked abducent 
 action of the two obliques (UBs); i. e., the eye will be adducted 
 slightly (to IJy). At C (the primary povsition), the abducent action 
 of the obliques balances the adducent action of the superior aud in- 
 ferior recti, so that the contraction of the four muscles will causi- 
 the eye to remain stationary. At D, on the contrary, the abductive 
 effect will preponderate somewhat, and the eye. already abducted 
 18", will be carried still further moderately outward< (to \h). At E. 
 i. e., when the eye is abducted 30°, the abducent effect is stiil more 
 pronounced (= EEs). 
 
 It is thus apparent that if all four muscles act together they will, 
 if the eye is being adducted or abducted, tend to carry it still further 
 in the direction in which it is goinq. They will, therefore, reinforce 
 the external rectus in abducting and the internal rectus in adductiui: 
 the eye, aud tlie amount of the reinforcement will increase in propor- 
 tion as the eye is already abducted or adducted. So that the in- 
 ternal rectus, for example, when it begins to contract (i. e.. is just 
 leaving the primary position at C) will receive little or no aid from 
 the contraction of the other four muscles, but. as it continues to act. 
 (e. g. at B). will be more and more assisted by them, and finally 
 when it reaches the limit of its contraction (at A) and is consequently 
 working at a great mechanical disadvantage, will be strongly rein- 
 forced. In like manner the external rectus will, as its own etticiency 
 diminishes with the increasing abduction of the eye, be assisted 
 more and more by the simultaneous contraction of the other mus- 
 cles. And it is altogether probable that it is in this way that the 
 outward and inward excursion movements of the eye are rendered 
 regular and uniform.* 
 
 *It may be noted that the action c*f the superior and inferior recti 
 in compensating for an increasdng feeblenes.s of the internal rectus 
 is shown in another way also. The internal rectus, as Weiss has 
 ])oiu(('d out (.\rch. f. Augenheilk; Vol. xxix). acts very much mori' 
 feebly when llic divergence of the orbits is great, i. e.. when the orbits 
 :ire sli:illi>w and the eyes far apart. Rut it is under just these condi- 
 tions that tlie sujierior iiud inferior recti act to most advautjige as ad- 
 ductors, .-^iiice. the gre:iter the divergeiic(> of the orbits, the greater 
 Ihe angle wliich the line of action of tliese two nmscies nutkes witii 
 tlie aiitero-i>osterior axis of tlu> eye. and tlie greater tMUsequently is 
 tlie l;iier;il effecl which tliev ar(> able to (>xi'rt. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 29 
 
 Our diagram may also be used to illustrate the action of the as- 
 sociated antayonists. If alongside of Fig. 3, which represents the 
 Held of axatiuu of the right eye, we place one representing the field 
 of fixation of the left eye (which may be done by turning Fig. 3 
 end for end, so that O is on tlie left and P on the right of the figure), 
 we shall see how the field of action (A2B.2C2D2E2), of tlie in- 
 ferior oblique of the right eye agrees in all respects with the field 
 of action of the superior rectus of the left eye. So also of the other 
 associated antagonists (R. superior rectus and L. inferior oblique; R. 
 inferior rectus and L. superior oblique; R. superior oblique and L. 
 inferior rectus). 
 
 Another point elucidated by the diagram is the amount and kind 
 of torsion movement (rotation of vertical meridian of the cornea) 
 produced by the various muscles. That is the Hue BBi represents 
 the fact that when the eye is adducted to B the superior rectus 
 will not only carry the eye itself upwards and inwards (to Bi), but 
 will also rotate the vertical meridian of the cornea so that the latter 
 will have the inclination BBi, i. e., will be inclined inwards. In a 
 similar way, the inferior oblique in the same situation will not only 
 carry the eye upwards and outwards (to B2), but will also 
 rotate the vertical meridian of the cornea outwards, so that it will 
 have the direction BB2. And the combined action of the two muscles 
 will be to give the vertical meridian the inclination BB^, i. e., one 
 of slight rotation inwards. So also BBe represents the inclination 
 of tlie vertical meridian of the cornea (viz., with the upper end 
 rotated inwards), when the eye is carried do'wnwards from a position 
 of adduction (B). Again, the fact that CC3 is strictly vertical shows 
 that when the eye is in the primary position it is not only carried 
 straight upw-ards by the combined action of the two elevators, but 
 its vertical meridian also remains vertical during the ascent. 
 
 It will also be observed that the combined action of the superior 
 and inferior recti or of the superior and inferior obliques, or of all 
 four muscles together will be not only to keep the eye in the hori- 
 zontal plane (in the line OP), but also to keep its vertical meridian 
 from rotating either to the right or to the left, as the eye is carried 
 outwards or inwards.* 
 
 In fact, all the various applications of the laws of Bonders and 
 Listing may be deduced from the study of thisi diagram. 
 
 Finally the diagram shows the limitation of the field of fixation 
 and the kind and amount of diplopia present in paralysis of any 
 one of the ocular muscles. Suppose, for example, that the superior 
 rectus is paralyzed. Then the field of fixation while normal below, 
 will, since the inferior oblique is the only elevator left, he repre- 
 sented above not by A3B3C3D3E3, but by A2B2C2D2E>. In other words, 
 when the attempt is made to elevate the eye as far as possible, it will 
 stand at A2, instead of A3, at B2, instead of B3, etc. Since its fellow eye 
 has a normal field of fixation and hence under the same conditions rises 
 to A3, B3, etc., the difference in position of the two eyes and conse- 
 quently also the amount and kind of diplopia produced will be repre- 
 sented by the difference between A2 and A3, Bo and B3, etc. The diagram 
 thus gives us a graphic representation of the fact that in paralysis of the 
 
 *E. g., at C the inward rotation of the vertical meridian produced 
 by the superior rectus will be represented by the angle C3CC2; this 
 
 inward rotation will be neutralized by the equal outward rotation 
 CeCC^, produced by the inferior rectus: and hence the combined 
 
 effect of these two muscles will be to keep the vertical meridian 
 
 from rotating either one way or the other. 
 
30 \i;\V CLASSIFICATION OK MOTOR ANOMALIES. 
 
 superior rectus the vertical diplopia increases rapidly when the eye is 
 carried upwards and outwards, wliile the lateral (crossed) diplopia in- 
 creases as the eyes are carried upwards and inwards. 
 
 The diagram may also be utilized to map out the field of fixa- 
 tion in cases of combined paralyseK. Thus the Held of fixation iu a case 
 of paralysis of both the superior rectus and the superior obliciue would 
 be represented by AoB.)02D.jE2K4l)4C4B4A4; and in a combined paralysis 
 of the superior and inferior rectus by AoBjCaDoE-iD.'iCsBsAs. 
 
 III. 
 
 THE TESTS EMPLOYED AND THEIR SIGNIFICANCE, 
 
 The object of the various tests that we make use of is to deter- 
 mine the following data : 
 
 (1). The precision and steadiness with which binocular fixa- 
 tion is effected (Static Tests). 
 
 (2). The ability of the eyes to move in various directions 
 while still maintaining binocular fixation (Dynamic Association- 
 tests). 
 
 (3). The ability of the eyes voluntarily to deviate from the po- 
 sition of binocular fixation (Dynamic Disassociation-tests). 
 
 These tests may be performed both for distance (with the vis- 
 ual lines parallel) and for near (with the visual lines converged). 
 
 The chief tests for binocular fixation are : 
 
 (1). Inspection with both eyes uncovered. This gives us 
 an approximate idea as to whether both eyes are directed at the 
 same object, a non-fixing eye appearing to deviate in, out, up. 
 or down, according to circumstances. 
 
 In making' this test we must be careful not to be misled by the 
 presence of a large angle alpha, which may simulate a deviation where 
 none exists. Any error on this score will be prevented by compar- 
 ing the findings with those of the screen test; for a deviation, great 
 enough to be noticeable upon simple inspection, will eertaiuly give 
 evidence of its presence by a distinct movement of the eyes when 
 the cover is shifted from one eye to the other. 
 
 (2) Fixation and Diplopia Tests. A patient with normal 
 eyes and perfect l)inocular fixation, will see distinctly with either 
 eye alone, or with both together, and will also see single. If 
 either eye or both fail to fix the object looked at, that object 
 will appear blurred (Fixation-test), and if one eye fixes and tlie 
 other docs not, the patient will in general see double ( Diplopia- 
 test), the image of the fixing eye being clear and that of the 
 other more or less shadowy and indistinct. The kind of diplopi:> 
 present indicates the nature of the deviation. Thus an /toniony- 
 inous diplopia (i. e., one in which the image formed by the 
 right eye is on the right side, and that formed by the left e\e imi 
 
NEW CLASSIFICATION OK MOTOR ANOMALIES. 
 
 :n 
 
 the left side) signifies abnormal converg-ence of the visual lines; 
 a crossed or hetcronyvious diplopia (in which the image of the 
 right eye is on the left side and vice versa) signifies lateral di- 
 vergence ; and vertica/ diplopia (in which one image is higher 
 than the other) signifies vertical separation of the visual lines, 
 so that one is higher than the other. The last-named variety 
 may be further differentiated into right diplopia, in which the 
 image formed by the right eye is below (indicating the condi- 
 tion in which the right visual line is the higher), and left diplo- 
 pia^ in which the contrary conditions prevail. 
 
 The amount of diplopia is precisely proportional to the amount 
 of deviation. It may be measured either by estimating the linear 
 distance between the two images, the distance of the object 
 looked at being also known,* or by determining the strength of 
 the prism which appropriately placed, will correct the diplopia.f 
 In order to differentiate the double images it is convenient to 
 use a light as a test-object, and have a red glass placed before 
 one of the eyes. By thus giving the two images a different colort 
 we enable the patient the better to distinguish between the two 
 and recognize the fact that diplopia exists; and, moreover, since 
 the red flame must belong to the eye covered with the red glass, 
 we can determine from the patient's statements as to the relative 
 place of the red and white images, whether we are dealing with 
 homonymous or crossed (lateral) or with right or left (vertical) 
 diplopia. 
 
 (3) Equilibrium Test. This is simply a variety of the diplo- 
 pia test. It consists of two steps. In the first an artificial ho- 
 monymous diplopia is produced by means of a prism of 12° or 
 more, placed 'base in, before the eyes. If the two images thus 
 produced are on a level, the visual lines themselves are on a level. 
 If, however, the right-hand image should be lower, there is really 
 a natural right diplopia present in addition to the artificial ho- 
 monymous diplopia, i. e., the right visual line is higher, or, to use 
 Stevens' nomenclature, there is right hyperphoria. The amount 
 
 *A linear distance of 1" between the images is equivalent to a 
 deviation of li/o° in the visual lines when the test-object is 1 metre 
 distant and to i/i° when the latter is 20 feet distant. 
 
 tA prism rarely measures the full amount of the diplopia, a-s a 
 prism which slightly undereorrects the latter nevertheles)S brings 
 the double images so close together that the residual correction can 
 be and is effected by the eyes themselves. 
 
 JA similar difference in character may be imparted to the images 
 by placing a Maddox rod or a Stevens' sphere before one eye; but 
 the red glass is simpler and, in comparison with the Maddox rod 
 at least, is less confusing to the patient and less apt to give am- 
 biguous results. 
 
32 NEW CLASSIFICATION OK .MOTOI{ ANOMALIES. 
 
 of this latter may be measured by the degree of prism, which, 
 placed base down before the right eye, will rectify the diplopia, 
 i. e., will bring the images on a level. In the next step of the test, 
 a strong prism is placed base down before the right eye, produc- 
 ing a marked vertical (left) diplopia. If both eyes are properly 
 adjusted for the object of fixation, the two images will be in a ver- 
 tical line. If, however, the upper image is to the right of the 
 lower, there is really, besides the artificial vertical displacement, 
 a natural homonymous diplopia, or, to use Stevens' expression, 
 there is an esopJioria. Similarly, if the upper image is to the left 
 of the lower, there is really a crossed diplopia or cxophoria. In 
 either case the amount of the esophoria or exophoria may be 
 measured by the strength of the prism which, placed base out or 
 base in will rectify the diplopia, i. e., will bring the two images 
 into a vertical line. 
 
 In Stevens' phoTometer, which is the best instrument for this pur- 
 pose, the measurement of the deviation is effected, not by placing 
 additional prisms before the eyes, but \>j revolving the prism that 
 lias been used to produce the initial latea'al or vertical diplopia until 
 the images are truly horizontal or vertical. The amount of rota- 
 tion is read off on an arc graduated so as to indicate directly 
 the amoimt of hyperphoria, esophoria, or exophoria present* 
 
 One defect of the equilibrium test is that patients often try in- 
 voluntarily to bring the two images into line and thus appear 'to 
 have no deviation of the visual lines, although one actually exists. 
 On the other hand, the involuntai-y movements set up in the attempt 
 made to compare two similar images placed at a distance from each 
 other may cause a deviation to be simulated where none is present. 
 I have seen this occur not infrequently— sometimes to a very marked 
 degree. The equilibrium test being thus apt to set up a certain 
 amount of muscular tension and hence disturb the tnie relation of 
 the visual lii-es, is in actual practice best performed after the tests 
 next to be described in which the eyes are under more normal 
 conditions. 
 
 (4) Screen Test. This depends upon the fact that the ten- 
 dency to binocular fixation is so strong that it still persists, even 
 when one eye no longer sees the object of fixation. If, therefore, 
 a card be placed before the left eye, and the gaze be directed at 
 a distant object, the left eye will, in case there is no disturbance 
 of innervation causing it to deviate, look straight at the object, 
 just as if the latter were still visible. If now the card is shifted 
 from the left eye to the right, the former being already properly 
 directed, will not have to change position in order to fix the ob- 
 
 ♦The same thing may readily be done with the ordinary trial- 
 frame, if we use in it a 12° prism and recollect that with this 
 each rotation of 5° from the horizontal represents 1° of hyperphoria, 
 and each rotation of 5° from the vertical 1° of esophoria or ex- 
 ophoria. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 33 
 
 ject, and will hence remain stationary. If, however, the left eye 
 when screened, deviates in any way, e. g. outward, it will, when 
 the screen is transferred to the right eye, have to turn inward, or 
 to the right, in order to fax the object, and the amount of its ex- 
 cursion inward (movement of redress) will be precisely equal to 
 the amount of its previous deviation. At the same time that the 
 left eye turns inward, or to the right, in order to perform fixation, 
 the right eye, which is now covered by the card and which, ac- 
 cording to the law of associated parallel movements, receives an 
 impulse to move to the right equal to that communicated to the 
 left eye, will move outward. 
 
 Whether it moves outward to the same extent that the left eye 
 moves in or not, depends upon the relative ability of the muscles 
 of the two eyes to respond to the stimulus imparted to them. If, 
 for instance, the left interuus is weak (paretic) a very strong impulse 
 will be required in order to make the muscle contract enough to 
 cause the eye to move in to the proper extent. According to the 
 law of association, an equally powerful impulse will be communi- 
 cated at the same time to the right externus; and, if the latter is 
 normally strong, it will respond much more efficiently to this im- 
 pulse than did the weak internus of the other eye, and will, con- 
 sequently, carry the right eye out much further than the left eye 
 was caiTied in. 
 
 It may be stated as a general rule (to which, however, there are 
 not a few exceptions) that in concomitant deviations the deflec- 
 tion behind the screen, and hence also the movement of redress 
 that the eye makes when the screen is removed, are equal for. 
 the two eyes, and that in non-concomitant deviations they are 
 unequal, being greater in the eye which has the more powerfully 
 acting muscles. 
 
 The screen test may also be used to ascertain ivhich oj th 
 two eyes habitually fixes. 
 
 In doing this the screen instead of being shifted from one eye 
 to the other is simply removed from the eye before which it is placed, 
 leaving both eyes uncovered. Each eye under these circumstances 
 will deviate when the screen is in front of it, and the other eye 
 will fix. If now the eye that is behind the screen is the one that 
 in binocular vision is regularly employed for fixation, it will move 
 into the position of fixation as soon as the screen is taken away, 
 and the other eye will deviate. If, however, the eye that is behind 
 the screen does not ordinaTily perform fixation, it will not move 
 when unscreened, and the other eye will continue to fix, i. e., will 
 remain steady in its place. That lis, the fact that the eyes perform 
 a movement" of redress when the right is unscreened and both are 
 left open indicates that the right eye haibitually fixes. If no move- 
 ment takes place, when the right eye is unscreened, the latter can 
 not be the eye that habitually fixes; and if no movement takes place 
 when the right eye and the left alternately are unscreened, there 
 must be an alternating deviation, i. e., one in which either eye in- 
 differently is used to fix with. 
 3 
 
34 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 The amount of deviation behind the screen, or of the move- 
 ment of redress made by the eye from which the screen has been 
 removed, may be roughly estimated by marks made upon the Hds 
 or may be more accurately determined with the perimeter or by 
 some of the various strabometric methods which have been well 
 described by Maddox ( A rchivcs of Op/it/i., XXL , 1 , 1892). An 
 angular deviation of l°-2° is generally sufficient to produce a 
 noticeable deviation behind the screen. 
 
 Finally, it must be n >ied that the sci-een test is valueless U7iless 
 the patient can be got to Jix with the uncovered eye. Hence, the 
 test is of no service in those who, owing to a deviation of long 
 standing, have lost the power of fixation; and it may likewise 
 prove nugatory in children who fail to keep their gaze directed 
 at the object that they are told to look at. 
 
 (5) Parallax Test. When the screen test is employed, the 
 patient, if his eye deviates behind the screen, will in general no- 
 tice a movement of the object whenever the screen is shifted. 
 This movement is called the parallax^ and, if the test-object is so 
 placed as not to be projected upon any surface back of it (e. g., if 
 it is a spot upon a blank wall), furnishes a valuable indication of 
 the amount and character of the deviation. The perception of 
 this movement is really nothing but the perception of a diplopia, 
 which differs from ordinary diplopia in the fact that the t^vo im- 
 ages are seen in succession^ instead of at the same ti/ne, and, as 
 they occupy different places, give the impression of a single im- 
 age which has moved from one place to another. Thus, if there 
 is convergence (esophoria), the right eye, when unscreened, and 
 before it has had a chance to assume the position of fixation, sees 
 the object a little further to the right than the left eye saw it, i. e., 
 the object appears to have moved from left to right (homony- 
 mous parallax). If, on the other hand, there is divergence (ex- 
 ophoria), the right eye will when unscreened see the object a 
 little further to the left than the left eye did when it was fixing, 
 i. e., the object appears to have moved from \\^\iio\G.ii( crossed 
 parallax). So, too, right hyperphoria is indicated by the fact 
 that the object appears to move down when the right eye is un- 
 covered (right parallax), while in left hyperphoria the object 
 seems to move up (left parallax). These various movements are 
 noticeable even when the deviation is verv slight; a hvpcrplioria 
 of 0.1", for example, being made ajipreciable bv a distinct up 
 and down movement of the object. 
 
 The amount of the parallax may be measured by the strength 
 of the prism which, placed before the eyes, will neutralize the 
 
NEW CLASSIFICATION OF MOTOR ANOMAMKS. 
 
 35 
 
 movement. Homonymous parallax will be neutralized by a 
 prism base out, a vertical parallax by a prism with the base up or 
 down, etc. The fact of neutralization or reversal is generally in- 
 dicated by the patient with great precision. 
 
 Tests for the Associated Parallel Movements. The ability 
 of the eyes to perform associated parallel movement^, i. e., the 
 range through which they can move in any direction and still 
 car'ry on binocular fixation, is tested in the same v^ ay as the abil- 
 ity to maintain binocular fixation while in the primary position. 
 All the tests just described are applicable. Thus inspection en- 
 ables us to say whether the movement of the eyes in, out, up, or 
 down, is too slight or too excessive; also the point where one eye 
 ceases to keep up with the other, this being shown by the fact 
 that the former visibly lags behind or wavers in its course. In: 
 this way we may map out the monocular ox bi)iocular field of fix- 
 ation, as may also be done more accurately by the fixation test 
 (with the double dot, as already described). So, too, by the 
 diplopia test we m-A}^ out ihe field of binocular single vision, and 
 thus also determine whether the eyes follow each other to a nor- 
 mal extent or not. With the same object in view we apply the 
 screen, parallax, and equilibrium tests to ascertain if there is 
 any visible deflection, parallactic movement, or heterophoria 
 within the limits of the normal field of fixation, and, if so, where 
 they begin, and in what direction they increase. 
 
 By these various means we determine whether the n?ovenicnis 
 in any given direction are excessive or restricted. In this re- 
 gard, inspection and the diplopia and screen tests are practically 
 the most applicable. The mapping out of the field of fixation is 
 laborious and, for the reasons already given, the results obtained 
 are very uncertain, unless a series of examinations upon the same 
 patient happen to be quite concordant. 
 
 On the other hand, the diplopia test is readily applicable, and in 
 my experience gives much more constant and reliable results.. 
 Diplopia may, to be sure, occur normally, as a transient phenom- 
 enon (physiolrgical diplopia) in most people when the gaze 
 is carried far towards the periphery of the field of fixation ; but 
 such diplopia, as already stated, is inconstant and superable by 
 voluntary effort. A diplopia occurring under all circumstances 
 as soon as the gaze has been carried from 35° to 40° from the 
 primary position, in any given direction, indicates an abnormal 
 weakness. This again may be temporar}-, and a diplopia of 
 this sort occurring about equallv far in all tlirections from the 
 periphery (concentric contraction of the field of single vision) 
 
36 NKW CLASSIKICATION uF MO I OK ANOMALIES. 
 
 indicates a temporary enfeeblenient of all the ocular muscles 
 such as may happen in neurasthenia and form one of the evi- 
 dences of a general depression of the muscular forces. On the 
 other hand, a diplopia, insuperable by voluntary efifort and con- 
 stantly occurring as soon as the gaze is carried 30° or less in 
 any given direction from the primary position, indicates a true 
 weakness or paresis, of some one of the ocular muscles (paretic 
 diplopia). The differential diagnosis of this condition, based 
 upon the character of the diplopia, will be touched upon later. 
 
 Tests for Convergence. The tests for binocular fixation in 
 convergence are the same as those for distance, namely, inspec- 
 tion, the fixation and diplopia tests, the screen and parallax tests, 
 and the equilibrium test. All of these, in fact, are habitually ap- 
 plied with the test-object held at the ordinary reading distance, 
 as well as at a distance of 20 feet. The test-object itself for the 
 examination at near points should, as Randall has well said, be 
 something requiring accurate fixation (e. g. a pen-point or fine 
 dot, mstead of the finger which is habitually used). In determin- 
 ing the parallax, some device such as a dot on a large card, which 
 does not allow the test-object to be projected upon any surface 
 beyond it, should be employed. 
 
 It must be borne in mind that, while orthophoria— absence of 
 deviation — is the ideal state for distance, a slight amount of di- 
 vergence is physiological for near. Thus, in testing at 12", we 
 expect to find with the phorometer an exophoria of 3° to 0°, 
 and with the screen a crossed parallax of the same, or a somewhat 
 less amount; and orthophoria at this range is actually to be re- 
 gf'.rded witi' suspicion, as probably indicating an undue tendency 
 to convergence. This fact does not militate against the exist- 
 ence in these cases of true binocular fixation for reading, or other 
 occupations requiring precise adjustments. 
 
 The tests for the associated movements in conveigence, like- 
 wise are made in the same way as for the associated movements 
 at a distance. In making the diplopia test at near it is best, if 
 using the candle, to hold the latter not less than 30'' from the 
 eyes, so as to reduce as much as possible the effects of projection. 
 If it is desired to determine the field of binocular single vision 
 for closer ranges, the effects of projection may be obviated by 
 using for a test-object a dot on a large card, the latter being tilted 
 sc; as ahvays to be perpendicular to the patitnt's line of sight. 
 
 A further important fact to determine in testing movements of 
 convergence is the convergence near-point (Pc). This is ascer- 
 tained by rnrrying a fine object nearer and nearer to the eyes, un- 
 
JEW CLASSIFICATION OK MOTOR ANOMALIES. 
 
 37 
 
 til tlio latter can no longer be converged upon it, or until it ap- 
 pears double. The distance of the object from the root of the 
 nc5-e may then be measured. Notice at the same time should 
 be taken as to which eye is the first to deviate when the limit'of 
 convergence is reached. The same test should be repeated from 
 either side, the object of fixation being first placed at some point 
 A to the right of the middle line and then carried directly towards 
 the left eye L. The latter obviously will not have to change its 
 position of rdduction, but the right eye, R, in order to follow the 
 object, must swing inwards through a considerable arc, A C P. 
 If, on repeating the test with the left eye, one of the two is found 
 
 Fig. 3. 
 
 to sag off from the test-object much sooner than the other eye 
 does, the former must have a relatively weak adducting power. 
 
 Not only the distance of the convergence near-point, but also 
 the ability of the eyes to maintaiii convergence at this distance, 
 should be noted. 
 
 Lastly, the C'liwergence must be tested by determining the 
 maximum strength of prism placed base out before the eyes, 
 which the latter can overcome when looking at a distant object. 
 Usually, if the patient can at the outset overcome a prism of 20° 
 refracting angle, with ease, w-e assume that he could readily learn 
 to do two or three times as much if sufificiently exercised, and we 
 consider his prism-convergence as normal. Exceptionally, es- 
 pfcially in cases of convergence-insufficiency, w^e find that the 
 
38 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 prism-convergence even after repeated trials cannot be got 
 above 10° or 12° (prism), and that even this amount is hard for 
 the palient to do and still harder to maintain. 
 
 As the exercise of the prism-convergence not infrequently be- 
 gets a condition of convergence-spasm, it is generally best to de- 
 fer testing the convergence in this way until after the divergence 
 has been determined. 
 
 1 1 is well in testing the convergence by means of adducting 
 prism to ascertain hoxv in7ich accommodation the patient is as- 
 sociating with it. This can be done by using the test-types for 
 the object of fixation and finding what concave glass is required 
 to give the patient full sight. It will generally be found that by re- 
 peated practice with an object of this sort, the strength of the 
 concave glass can be gradually diminished — i. e., the patient 
 gradually acquires the ability, when looking at a distant object, 
 to converge without using his accommodation. A case in which 
 extreme facility in this respect was acquired has already been 
 spoken of. It is often important therapeutically to efifcct a dis- 
 association of this sort between accommodation and convergence, 
 especially in cases of convergence-insufficiency. 
 
 Tests for Divergence. The diverging power is determined 
 by the amount of jjrism placed, base in, before the eyes, which 
 the latter can overcome when looking at a distant object. The 
 strength of prism thus overcome varies in normal cases from G° 
 to 8° (refracting angle). A divergence of less than 5° (prism) 
 means insuflficiency, and one of over 9*^ an excess of diverging 
 action. 
 
 Tests for Sursumvergence. The sursumvergence, l e., the 
 amount by which the eyes can diverge in a vertical plane, is de- 
 ternnned by the strength of prism placed base up or down before 
 the eyes, which the latter can overcome when looking at a dis- 
 tant object. The right snrsumvcrgejice (in which the prisms are 
 so adjusted as to cause the right visual line to be the higher of the 
 two) and the left sursumvergence should both be ascertained. 
 It is usually best to leave some interval of time between the two 
 tests, as after making the efifort required to produce right sur- 
 sumvergence (or left deorsumvergence) it is difficult at once to 
 perform the contrary action. 
 
 A difference of 1° or more between the right anil Ictt sursum- 
 vergence or, in any case, a sursumvergence exceeding *1° (prism), 
 indicates the probable existence of a hyperphoria. 
 
NEW CLASSIFICATION OF MOTOll ANOMALIES. 39 
 
 Way in which the Tests are applied in Practice. In prac- 
 tice I have found it best to apply the tests in the following order: 
 
 (1) Inspection, I note the apparent relations of the eyes in 
 the primary position and also for associated parallel and con- 
 vergent movements, using for the purpose some rather fine test- 
 object such as a pen-point which the patient is made to follow 
 with the eyes as it is carried in different directions. Any very obvi- 
 ous deflection, e. g., a marked concomitant strabismus or a par- 
 alytic squint, can be made out at once by this means alone. 
 
 (2) Screen and Parallax Tests. These are made simultan- 
 eously. First, a test-object 20 feet off is taken, and then one at 
 the ordinary reading distance. If inspection has revealed any 
 marked deviation or one which increases notably in any given 
 direction of the gaze, the screen test also is applied in different 
 portions of the field of fixation in order to corroborate these find- 
 ings. 
 
 (3) Equilibrium Test both for distance and near with the 
 phorometer or with prisms in the trial-frame. 
 
 (4) Test for Divergettce by means of prisms placed base in 
 before the eyes (Abducticn-test of most authors). 
 
 (5) Determination of the Convergence Near-point both in 
 the median line (test for bilateral convergence) and also, as has 
 been previously explained in the course of this brochure, in 
 lateral positions of the gaze (test of eccentric convergence). 
 
 (6) Test for Convergence by prisms placed base out before 
 the eyes (Adduction-test of most authors). 
 
 (7) Diplopia Test with candle at 40" or more, and some- 
 times also with card and dot at XT'. In order to make this test 
 available for diagnosis we must Have some ready method of re- 
 cording which shall indicate, not only the character of the diplo- 
 pia, but also its approximate amount, the point at which it be- 
 gins to appear, and the way in which it increases or decreases in 
 different directions of the gaze.* 
 
 These comprise all the tests really necessary, and all these can 
 in most cases be readily performed within ten minutes. If 
 further tests are thought requisite, the Sursumvergence Test (8) 
 
 *A sample of the scheme which I have adopted for my entries is 
 as follows: 
 
 Eu 20", Er 25^^— DL; Eu 25^, Er 30«-DL 2", DX 2", which would 
 mean that when the eyes were carried 25°, to the right and 20° up 
 from the primary position vertical diplopia appeared: the image 
 of the left eye being lower (left diplopia): and that when the eyes 
 were carried 30° to the right and 25° up the image of the left eye 
 was 2° below and 2° to the right of that found by the right eye 
 (i. e., there was a left and crossed diplopia of 2° each). 
 
40 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 and the mapping out of the Field of Fixation (9), may be under- 
 taken. If they are, they should be left to the last, as they gener- 
 ally cause considerable strain of the eyes, and hence, if performed 
 early, are apt to derange the normal relations of the eyes, and 
 thus interfere with any tests that may be made afterwards. 
 
 If the patient is ametropic or presbyopic, the various tests enu- 
 merated should be made both with and without the correcting 
 glasses, in order to ascertain the effect of the latter upon the mus- 
 cular condition ; and other factors that might modify the latter, 
 e. g., the existence of atropine mydriasis, should also be noted. 
 
 (To be continued.) 
 
Reprinted from Annals op Ophthalmology, January, 1897. 
 
 A NEW CLASSIFICATION OF THE MOTOR ANOMA- 
 LIES OF THE EYE, BASED UPON PHYSIO- 
 LOGICAL PRINCIPLES. 
 
 the prize essay of the alumni association of the college of 
 physicians and surgeons, new york, for 1896. 
 
 By Alexander Duane, M. D., 
 
 NEW YORK. 
 
 Part 2. Pathology. 
 
 IV.. Classification of Ocular Deviations. Nature of functions 
 that may be affected.— Nature of lesions affecting these functions. 
 — Hypokinesis, Hyperkinesis, Parakinesis.— Variation in degree 
 of the lesions. Superable and insuperable deviations (Hetero- 
 phoria and Squint) .—Classification propounded.— Comitant and 
 non-comitant deviations.— General diagnostic laws based upon 
 the presence or absence of comitancy.— Transformation of non- 
 comitant into comitant deviations. 
 
 V. Anomaliesoftlie Individual Muscles. Muscular under-action 
 and over-action. Three main varieties.— Structural muscular de- 
 viations. Structural (Muscular) squint (Sclineller's cases). 
 Structural heterophoria.— Insertional squint and heterophoria.— 
 Innervational deviations. Muscular Paresis. Muscular Spasm; 
 varieties and cases.— Symptoms and Differential Diagnosis of the 
 different Varieties of Muscular Over-action and Under-action. 
 Identity in the symptoms presented by the three varieties. Con- 
 genital deviations. Course of acquired deviations. Diagnosis 
 between under-action and over-action. Slight weakness and 
 over- action (explaining cases of heterophoria and particularly 
 hyperphoria). Diagnosis by the double images. Principles and 
 diagnostic tables. Deductions from the tables. Treatment of 
 muscular over-action and under-action.— Tremor of individual 
 ocular muscles; Unilateral nvstagmus. 
 
 VI. Anomalies of Associated Parallel Movements. Hypokm- 
 sis. Paresis and insufficiency of associated parallel movements. 
 Spasm of associated i.arallel movements. Peculiar case of spasm 
 observed by the autliov.— Parakinesis of assocuited movements 
 (Nystagmus). Theory of nystagmus. 
 
 VII. Anomalies of Convergence. Hypokinesis. Paralysis of con- 
 vergence.— Convergence-insufficiency. Signs. Nature and etiol- 
 
42 XEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 ogy. Varieties of non-accommodative convergence-insufficiency. 
 Accommodative convergence-insufficiency; varieties. Course. 
 Complications. Symptoms. Treatment. — Hyperkinesis. Spasm 
 of convergence. Convei'gence-excess. Signs. Etiology. Va- 
 rieties of non-accommodative and of accommodative converg- 
 ence-excess. Course. Complications. Symptoms. Treatment. 
 
 VIII. Anomalies of Divergence. Hypokinesis. — Divergence-insuf- 
 ticieucv. Signs. Etiology. Idiopathic and secondary diverg- 
 ence-insiifticiency. Differentiation of the two forms. Course. 
 Symptoms. Treatment. — Hyperkinesis. Divergence-excess. 
 Signs. p]liology. Primary and secondary divergence-excess. 
 DiftVrciitiatioii of the two. Course. Symptoms. Treatment. 
 
 IX. Anomalies of Sursumvergence. Hypokinesis. Sumsurverg- 
 encc-ins\ifficit'iicy. — Hyperkinesis. Sursumvergence-excess. 
 Sursunivergencc-liyperphoria and vertical strabismus. Peculiar 
 cases; anatr()i)ia and catatropia. 
 
 X. Anomalies of Rotation Movements. 
 
 XI. Recapitulation. Nature of Outward, Inward and Vertical 
 Deviations (Exoiihoria. Plsophoria and Hyperphoria). Varieties 
 of each and their dilferentiation. 
 
 IV. 
 
 THE CLASSIFICATION OF OCULAR DEVIATIONS. 
 
 We have seen in Section II. of this brochure that as 
 physiologists we have to consider not only the movements 
 of the individual muscles and the relative power of the 
 latter, but also, and more particularly, the associated move- 
 ments of the eyes produced by the coordinated actions of 
 these muscles. It seems obvious that the same principles 
 which we apply to the physiology of the ocular movements 
 should also be applied to their pathology, and that in classi- 
 fying motor disorders of the eye we should concern our- 
 selves not simpj}! icith the disorderi< and weaknesses of the 
 Duisrhs as such, hut also with the affections of all the various 
 QHOvements of which either e//e alone or both et/es together 
 are susceptible. Reasoning in this way, we shall ask if we 
 do not in actual practice meet with pathological conditions 
 which may be classified into the following groups, corre- 
 sponding to the physiological groups which we have al- 
 ready studied? 
 
 (1) Disorders of individual muscles. 
 
 (2) Disorders of associated parallel movements. 
 
 (3) Disorders of convergence. 
 
 (4) Disorders of divergence. 
 
 {5j Disorders of sursumvergence. 
 
 (6) Disorders of the rotation (or swivel) movements. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 43 
 
 I think that we have a sufficient number of clinical facts 
 to enable us to give an affirmative answer to this query. 
 
 For example, we meet with quite a number of cases in 
 which the power of convergence is weak — a state that we 
 might attribute (as indeed it often is attributed) to an in- 
 trinsic weakness of the interni, were it not for the fact that 
 the working of the latter in associated parallel movements 
 is quite normal. Here then, evidently, it is the function of 
 convergence that is at fault and not the action of the in- 
 terni per se. Similarly we find excessive divergence action 
 which can not be attributed to weakness of the interni, 
 since the latter act normally both in convergence and in 
 lateral movements, nor yet to excessive strength of the ex- 
 terni as such, since the latter in associated parallel move- 
 ments do not carry the eye too far outward. In this case, 
 therefore, it is the function of divergence, and not the 
 power of the interni, or externi, that is at fault. Both this 
 condition and the preceding one exhibit the common symp- 
 tom of divergence in fixation and would hence ordinarily 
 be classed together as examples of exophoria; but in classi- 
 fying them thus we should be naming not the disease but 
 the symptom. The symptom, moreover, while the most ob- 
 vious, is not necessarily the most important feature of the 
 condition in question ; and in our therapeusis we aim not 
 so much to abrogate the exophoria per se, as to remove the 
 state (defective convergence, excessive divergence) caus- 
 ing the exophoria. 
 
 Similar instances might be given of other varieties of 
 motor disorders in which also the function involved is an 
 ocular movement and not an ocular inuftcle. The considera- 
 tion of these, however, will be deferred until later when 
 they can be discussed more in detail ; those given above 
 being regarded as sufficient for purposes of illustration. 
 
 If, then, any one of the ocular motor functions may be 
 involved independently of the rest, we must next inquire 
 what may be the nature of the lesion affecting it. In ans- 
 wer to this it may be said that any motor function may be 
 deranged in either one of three ways. 
 
 (1) It may be performed inadequately or not at all — de- 
 ficiency of moyement ( II//2>ol-i)ie.sis). 
 
44 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 (2) It may be performed excessively — excessive move- 
 ment ( JIi/perK'inesis). 
 
 (3) It may be performed irregularly or in successive 
 phases of excess and inadequacy — irregular movement 
 ( Parakinesis). 
 
 To the question whether disorders having these various 
 characters are actually encountered in connection with the 
 ocular movements, clinical facts once more enable us to 
 give an affirmative answer. It must, however, be under- 
 stood that these conditions, namely hypokinesis, hyper- 
 kinesis and parakinesis, may be present in very varying 
 degrees. Thus weakness (hypokinesis) may vary all the 
 way from a slight and transient enfeeblement to a complete 
 paralysis; and, similarly, excessive action (hyperkinesis) 
 may range from a moderate degree of over-action to an 
 intense and permanent spasm. It thus happens that there 
 are some deviations so slight as to be habitually corrected 
 by the supplementary ^ffort that the patient is able to ex- 
 ert ( Supe fable deviation, Latent st)'ahis')nus,IIeteropJioria ); 
 while there are other deviations so great that the patient 
 can overcome them with difficulty if at all, and which are 
 hence more or less constantly present ( Insuperable devia- 
 tion. Manifest squint, Ileterotropia ). These latter again 
 are divided according to the constancy of their occurrence 
 into Interniitte]it, when present at intervals, Periodic, when 
 recurring regularly under certain conditions {e. g. in con- 
 vergence), and (Jonsta)it. It should be borne in mind, 
 however, that these distinctions all represent differences 
 simply of degree and not of kind. 
 
 The foregoing considerations, confirmed and modified by 
 the results of the examination of quite a large amount of 
 clinical material, have led me to propound the following 
 classification of the motor anomalies of the eye. 
 
 CLASSIFICATION OF THE MOTOR ANOMALIKS OF TIIK 
 EYE. OCULAR DEVIATIONS IN (JENERAL DUE To 
 
 L Anomalie.s of Iiulividual IMusclcs oi- of tlicir Nfivc-iiucU'i. 
 {a) Jhider-actioti. The iiiusclf works iiiclliciciitly. 
 L Hecause tiic niusrit' itsi'If is ill-di'volopi'd or atropliii-d (Struc- 
 tural S(|uint), or because its attachnieuts are unfavorable for 
 
 cfTcctive action ( Iiiscrtioual Scuiiiit). 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 45 
 
 2. Because of iinpairinent of the nerve or nerve-iiueleus supply- 
 ing the niusele (Paretic S<iuint). 
 (h.) Orer-action. Tlie nuisch- works excessively. 
 
 1. Because the muscle itself is over-developed (Structural Squint) , 
 
 or because its attachments are favorable for effective action 
 (Insertional Squint). 
 
 2, Because of over-excitation of the nerve or nerve-nucleus sup- 
 
 plying the muscle (Spastic Squint), 
 (c.) Perrerted action. Clonic spasm of individual nniscles (some 
 rare forms of Nystagnuis) . 
 
 II. Anomalies of the Association Centres for Parallel Movements. 
 {a.) Under-action. Producing an equal impairment in the move- 
 ment of both eyes either (1) up, (2) down, (3) to the right, 
 (4) to the left, or (5) obliquely, or (6) an equal impairment 
 of the rotary (swivel) movements of the two eyes. (Associ- 
 ated Paralysis, Conjugate Paralytic Deviation.) 
 
 {b.) Orer-action. Producing an equal excessive movement of both 
 eyes in the same direction (Associated Spasm, Conjugate 
 Spastic Deviation) . 
 
 (c.) Perverted action. Clonic Spasm (Ordinary Nystagmus; includ- 
 ing Lateral, Vertical, Rotary and Mixed Nystagmus). 
 
 III. Anomalies of the Centre for Convergence-Movements. 
 
 (rt.) Under-action. Convergence-Insutftbiency (producing one va- 
 riety of Comitant Divergent Squint or Exophoria) . 
 
 1. Accommodative (due to relaxed accommodation in myopes). 
 
 2. Non-accommodative. 
 
 {h.) Orer-action. Convergence-Excess (producing one form of 
 Comitant Divergent Strabismus or Esophoria). 
 
 1. Accommodative (due to excess of accommodation in hyperme- 
 
 tropes.) 
 
 2. Non-accommodative. 
 
 IV. Anomalies of the Centre for Divergence Movements. 
 
 {a.) Under-action. Divergence-Insuificieney (producing one form 
 of Comitant Convergent Squint or Esophoria). 
 
 {b.) Orer-action. Divergence excess (producing one form of Com- 
 itant Divergent Squint or Exophoria) . 
 
 V. Anomalies of Sursumvergence. 
 
 («.) Under-action. Sursumvergence-Insufficiency. 
 
 (b.) Over-action. Sursumvergence-Excess (producing constant or 
 intermittent vertical divergence of the visual lines: includ- 
 ing cases in which one visual line is habitually above (Spas- 
 tic Right or Left Hyperphoria), and cases in which some- 
 times one, sometimes the other, rises higher (Alternating 
 Hyperphoria) . 
 
 VI. Anomalies of Rotation (Swivel or Torsion) Movements. 
 
 (rt.) Habitual or intermittent divergence of the Vertical meridians 
 
 (Cyclophoria Divergens). 
 {b.) Convergence of the vertical meridians (Cyclophoria Couverg- 
 
 ens) . 
 
46 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 VII. Mixed Forms. Many varieties iiiehidinfi: particularly — 
 
 (a.) ('(mverffeiice-Iusuffieieiu'y combined with Diverg'ence-Excess. 
 
 (h.) Convergfence-Iiisiiilicieiicy comhiiicd with Diverfj^ence-Insuffi- 
 ciency. 
 
 (c.) Coiivertji'iice-lnsutticiency, simple or complicated, combined 
 with under-actioii or over-action of one or more of the lat- 
 eral or vertical muscles. 
 
 (d.) Convergence-Excess combined with Divergence-Insufficiency. 
 
 (c.) Convergence-Excess combined with Divergence-Excess. 
 
 (/.) Convergence-Excess, simple or complicated, combined with 
 under-action or over- action of one or more of the lateral or 
 vertical muscles. 
 
 {g.) Under-action of one nuiscle combined with over-action of 
 another. 
 
 Before taking up the study of the individual anomalies, 
 it is well to consider one or two features common to all of 
 them. 
 
 Comitant* and Non=comitant Deviations. A wide differ- 
 ence exists both as regards symptoms and physical signs 
 between motor disorders in which the amount of deviation 
 constantly changes according to the direction of the gaze 
 ( Non-coinitant deviations) and those in which it remains 
 the same ( Coniifant deviations). The former is apt to be 
 much the more troublesome of the two to the patient, par- 
 ticularly when the deviation keeps changing while the eyes 
 are executing associated parallel movements. This is ap- 
 parently due to the fact that the symptoms occasioned by 
 the deviation, changing as they do with every alteration in 
 the position of the eyes, cannot be allowed for nor be as 
 readily ignored as when they are constant. 
 
 That is, since the patient sometimes sees single, sometinu^s doul)le, 
 i. e. is affected with an error of varying amount, he cannot as readily 
 make allowances for his peculiar state of vision as if he saw double 
 all the time and had a constant error to contend with. Moreover, it 
 is less easy for the eye to suppress a false inuige when the latter, in- 
 stead of occupying always the same .spot upon the retina, as it does 
 in comitant deviations, occupies a nund)er of different spots in suc- 
 cessif)n, as it does in the case of a non-comitant deviation. Hence 
 the diplopia tends to persi.st much longer in non-comitant disorders 
 than in those that are comitant. Besides, the very fact that the de- 
 flection is changeable in amount is the cause of the most trying syinp- 
 toms (false projection and vertigo) of a non-comitant deviation; and 
 
 •Tlic word "comitant" is lure- i-niiiloytd in preference to tlif more usual "ecu 
 comitant " as lieinn botli l)riifir and ctynioloKically better. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 47 
 
 when the deflection becomes constant in (juantity for all directions of 
 the gaze, these symptoms are apt to disappear. 
 
 It is obvious that an (ifftction of the individtad ucular iiiia^clcs. 
 whether in the direction of excess or of deficiency, must cause a 
 non-comitant deviation, the angle between the two visual lines be- 
 coming greater and greater the more the eyes are carried in the 
 direction in which the muscles in question normally exert their great- 
 est influence. Thus in a paralysis of the right externus the right eye 
 will lag more and more behind its fellow in proportion as the eyes 
 are carried to the right; and in paralysis of the right superior rectus 
 the right eye will fall more and more below the level of the other, 
 the more the attempt is made to direct the gaze up and to the right. 
 In fact, it is by this very changeableness or non-comitancy of the 
 deviation that we make our diagnosis of the existence of muscular 
 paralysis or spasm. 
 
 On the other hand, a deviation due simph^ to an over-action or 
 under-action of either dirercjencc or convergence will not change in the 
 performance of associated lateral or vertical* movements, as long as 
 the object of fixation does not appreciably approach or recede from 
 the eyes. For, for any given distance, the amount of convergent or 
 of divergent action will be constant and the excess or deficiency of 
 this action will also be constant, no matter whether the eyes are look- 
 ing straight ahead, or laterally, or up or down. If, however, the dis- 
 tance of the object of fixation from the eye is altered, the amount of 
 convergent or divergent action changes also, and in general the 
 amount of deflection will change as well. Thus in a pure conver- 
 gence-insufficiency the deviation will become more and more appar- 
 ent as the limit of convergence is approached and will disappear alto- 
 gether when the convergence is relaxed, i. e. when the patient is 
 looking at a distance. In the case of a divergence-insufiiciency the 
 reverse will hold good. 
 
 In anomalies of associated parallel movements the motions of the eyes 
 are strictly comitant, and in fact the visual lines remain everj-where 
 parallel, since the ocular movements, while either restricted or in ex- 
 cess in some given direction, are restricted or in excess to the same 
 degree in both eyes. For example, in a case of restricted sursum- 
 version both eyes will fail to move up, but as the failure affects both 
 to an equal degree, the visual lines will in the performance of this 
 movement remain parallel up to the point where they cease to move 
 at all. 
 
 The foregoing facts may be recapitulated as follows : 
 (1) A deviation which increases or decreases in the per- 
 formance of associated paraUel movements hy the eyes signi- 
 Jies an anomali/ of one or more of the ocular muscles — the 
 
 ♦This statement is not absolutely accurate, for, owing to the fact that the visual 
 lines tend to diverge when the gaze is directed upward and to converge when they 
 are directed downward, an exophoria otherwise comitant will show an increase in 
 the upper and a decrease in the lower portions of the field of fixation. 
 
48 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 direction in which it increases corresponding to that in 
 which the action of the muscles affected is normally most 
 pronounced. 
 
 (2) ^1 dtrii(ti())i irjiirlt rotiai iiK.coustant or nearl// soir/dle 
 the eijes are perform uui paraUel movements i,s due, not to an 
 anomah/ of indh'idual muscles, bat to an anomaly of some 
 one of the associated movements of the eyes. 
 
 (3) A deviation lohich increases as the eyes are converged 
 denotes a convergence-anomaly, and one ivhich increases as 
 the eyes are passing from co))rerrience to i)ara]lelisnt a diver- 
 gence-anomaly. 
 
 Transformation of Non=comitant into Comitant Devia= 
 tions. Non-comitancy in parallel movements might be 
 remedied by restricting or increasing the action of the un- 
 affected eye in the same sense as that in which the action 
 of the affected eye is restricted or increased; /. e. by con- 
 verting the anomaly from one of Class I. into one of 
 Class II. 
 
 This is done in actual practice when, c. f). in a paralysis of the su- 
 perior oblique of the right eye we teuotoniize its associated antaj?on- 
 ist, the inferior rectus of the other eye, thereby weakening the lat- 
 ter artificially in precisely the same sense and to the same extent 
 that the right eye is weakened naturally. In nature a similar, though 
 less perfect, result is commonly attained l>y the deA'elopment of a 
 spasm of the direct antagonist or of a pair of antagonistic muscles in 
 the eye ai¥ected. Thus in a paralysis of the right externus, wliich 
 produces a deviation confined to the right- half of the field of fixation, 
 is usually followed after a time by a spastic contraction of the right 
 internus, which produces a deviation of the same character in the 
 left half of the field of fixation. Thus the affected eye gets' to squint 
 inward, not only when looking to the right, but also when looking to 
 the left, and the deviaticm, from being markedly non-comitant, be- 
 comes comitant or nearly so. A similar occurrence is regularly ob- 
 served in paralysis of the other nuisdes. 
 
 A similar tendency to replace non-comitant by comitant deviations 
 appears to prevail, although possil)ly 1<> a less extent, in divergence 
 and convergence anomalies. Thus a convergence-insufficiency, exist- 
 ing at first without any complication, is very apt later on to become 
 associated with a divergence-excess, so that a sensibly constant devia- 
 tion outward(exoi»horia)is present both for far and near.where origin- 
 ally it was i)resent for lu-ar only. So also a convergence-excess may 
 lead to a divergence-insufiiciency, so that the I'sophoria which at first 
 was marked only for lu/ar now becomes etjually pronounced for dis- 
 tance. Tliis compensatory process, by which comitancy is evolved 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 49 
 
 <nit of a iion-coiuitant state, is doubtless the ivason for the many 
 iuixe<l forms of divergence and convergence anomalies that we meet 
 with; and the process itself may actually be watched in following 
 the develoj^meiit of many cases of squint. 
 
 The process in fact seems to take place so generally that 
 it seems safe to enunciate the following law: 
 
 .1 iioii-ronrifant deviation u.sualft/ feuds to become comi- 
 frnit, there heing superadded to the morbid condition already 
 existing another Inj means of ichich the former is generalized 
 and rendered sensibly equal throughout the whole Jield of 
 fixation. 
 
 V. 
 
 ANOMALIES OF THE INDIVIDUAL MUSCLES.* 
 
 liypokineses and Hyperkineses ( Paretic and Spastic 
 Squint), Over-action or under-action of the individual 
 ocular muscles, giving rise to a disturbance of the normal 
 balance of the eyes, may be due to 
 
 (a) Over or under - development of the muscle itself 
 (structural squint, structural heterophoria). 
 
 (b) Variations in the origin, insertion and direction of 
 the muscles and in the length of their tendons (insertional 
 squint or heterophoria) . 
 
 (c) Over or under-excitation of the muscle due to some 
 affection of its nerve or nerve-nucleus (paretic and spastic 
 squint and heterophoria) . 
 
 The hypertrophy or the non-development of the muscles, 
 producing what I have called structural deviation is prob- 
 ably in many cases congenital. This is certainly so in those' 
 cases of defective elevation of the eye (frequently asso- 
 ciated with ptosis) which have been proved by dissection 
 to be due to absence of the superior rectus (Fuchs). I 
 have seen one marked instance of this congenital anomaly 
 in which ptosis co-existed with almost entire absence of 
 elevation, and I am inclined to think that several other 
 cases of less complete paralysis of elevation, which I have 
 
 ♦This section, since its first presentation to the Prize Committee, has been largelv,- 
 added to and to a certain extent re-modeled. 
 
-50 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 observed, were likewise congenital and structural in origin.* 
 
 Another class of cases of structural deviation, of quite 
 frequent occurrence, are those which Schneller (Arch, fiir 
 Ophth. xxiii. No. 3) describes under the name of itniscnlar 
 sfrabi.'imiis. Such, for example, are those cases of diver- 
 gent strabismus in which, at the time of operation, we find 
 the external rectus thick, broad and fleshy, and provided 
 with a dense, broad tendon, while the internal rectus, on 
 the contrary, is thin and has a narrow tendon, often split up 
 into separate fibrils. Schneller in these cases found that 
 the tendon of the externus, instead of being about equal to 
 that of the internust, was from one-fourth to one-third 
 greater. In convergent strabismus, on the other hand, the 
 ratio was reversed, the tendon of the externus being much 
 thinner than that of the internus and the externus itself 
 being comparatively meager and undeveloped, 
 
 Schneller reports thirty-four cases of such muscular 
 (structural) strabismus. He regards them (probably with 
 justice) as congenital in origin. 
 
 Otliers have supposed that these were cases of acciuired atrophy 
 (atrophy of disuse). But the patlioloj^ical ehang'es are those of sim- 
 ple non-devek)pnieiit rather than atrophy, the inuseuhir fibres being 
 merely insutheient in number or size and showings: no e>idenees of 
 fatty or filn-ous transformation nor of myositis. 
 
 The diagnostic features of a muscular squint, according 
 to Schneller, are 
 
 (1) The deviation is not relieved by atropinization and 
 correction of the refraction (distinction from accommoda- 
 tive convergence-excess and convergence-insufficiency). 
 
 (2) The field of fixation (/. e. the range of excursion of 
 the eyes) is abnormally large in one direction and abnor- 
 mally limited in the opposite. If the sum of the inward 
 excursions of the two eyes exceeds the sum of the outward 
 excursions by 30'\ a convergent strabismus is produced ; 
 while a preponderance of outward excursions over inward 
 excursions of 12' is sufficient to cause a divergent squint 
 (Schneller). 
 
 *Scc article by tlK- autliur 1)11 •■ I'aialysis of tlic SiiiHii.>r Kutu-^ aiul Us HcnriiiK 
 upon tilt Theory of Mustular Iiisufricicncy " (Archives ol t)i)lit!ialiiiolu),'y. vol. xxiii.. 
 No. 1,18M.) 
 
 tSchnellcr fotiud the normal ratio between the breadth of the externu.s-tendoii 
 and the internu.s-tendoii to be 102:100. His measiircnients were made so as to include 
 more uf the .-scleral attachments than in those made by other observers who have 
 found the ratio to be SS ( Volkiiiaiiu) ami S<( ( [•"uclis) 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 51 
 
 This latter statement involves a fallacy, strictly speaking?, if the 
 range of excursion is, as is usually the case, determined by making 
 the eyes follow a test-object situated within a foot or so of the eye. 
 For in this case when the eyes are directed to the right, the amount 
 of excursion outward of the right eye = the absolute amount by which 
 the externus can turn it outward (abduction) less the amount by 
 which it is turned inward in order to converge upon the object (con- 
 vergence). The latter (convergence) movement will be exce^ssive 
 either if the right iiitei'nus acts too forcibly in response to an ordi- 
 nary impulse of convergence (muscular excess) or if, the muscle 
 being normal, the impulse itself is excessive (convergence-excess). 
 In either case the net movement outward will be limited, even when 
 the actual amount of abduction produced by the externus is normal. 
 If, then, the case were one of simple convergence-excess the limita- 
 tion of outward movement would be the same for both ej'es, 
 (. e., the same whether the gaze is directed to the right or to the 
 left; but if it were one of muscular squint, i. e. of actual 
 insufficiency of the externi (or preponderance of the interni) 
 the limitation might be either unilateral or bilateral. In the latter 
 event the diagnosis of a muscular anomalj', as distinguished from a 
 pure anomaly of convergence, would be substantiated if the limita- 
 tion of abduction were found to be the same for all distances, far as 
 well as near. 
 
 Degrees of weakness or of over-development, too slight 
 to produce actual squint, probably form an important ele- 
 ment in the causation of many cases of heterophoria (".s'/r^^r- 
 fura/ heteropJioria. ) 
 
 Insertional squint or heterophoria, /. e. that sort of mus- 
 cular under-action or over-action due to variations in the 
 origin and insertion of the tendons, is difficult to distin- 
 guish from the structural deviations due to under or over- 
 development of the muscular fibre itself. The structural 
 deviations, however, are frequently congenital, while inser- 
 tional squint is generally acquired. For example, a very 
 important class of cases coming under the latter category 
 are those in which the insertion of a tendon has been dis- 
 placed by a tenotomij or an advanremenf . Here by the op- 
 eration an insertional anomaly is produced; and the weak- 
 ness or over-action resulting from this artificial anomaly is 
 precisely similar in symptoms and objective signs to weak- 
 ness or over-action due to natural causes (paresis or 
 spasm, for example).* 
 
 *Of the exactness of this similarity I have been able to convince myself by re- 
 peated examinations upon cases in which extensive operations had been made either 
 upon the lateral or vertical muscles. 
 
52 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 Another class of cases in which there is an acquired in- 
 sertional anomaly are those in which a direrr/enf sfrahis- 
 mus /ia.s (Jrveloj^ed as a rcsti/f of tlie (jradual dit-erffence of 
 the ovhits taking place during the period of growth in child- 
 hood and youth. This divergence, by altering the angle 
 of insertion of the tendons and the amount of tendon in 
 contact with the eye -ball, increases very greatly the power 
 of the externus and diminishes that of the internus, and in 
 itself is quite sufficient to account for the development of 
 the strabismus (see L. Weiss, Arch. f. Augenh. xxix. and 
 Arch, of Oph. xxv. No. 3, 1896) . The anomaly in this case 
 is of great importance in that it exaggerates and renders 
 uncertain the effect of a tenotomy of the interni when made 
 upon children. Admitting Weiss' s explanation of it, the 
 obvious deduction would be that tenotomy of the interni 
 should be avoided in children with convergent squint who 
 have the orbits and eyes set very close together, since in 
 these divergence of the orbits is likely to take place subse- 
 quently resulting in a preponderance of the externi, which 
 will by itself suffice to correct the convergence. 
 
 Other kinds of insertional anomalies exist, some so slight 
 as to produce only a moderate degree of heteropliona, in- 
 stead of a squint. They often develop when a non-comi- 
 tant deviation has lasted for some time, and help to trans- 
 form the latter into a deviation of the comitant variety. 
 
 Muscular paresis and spasms (Innervational Deviations). 
 The subject of the paralyses of the eye muscles has been 
 so thoroughly worked out and so ably presented by the two 
 Graefes and Mauthner, that there is but little to add to their 
 statement. The few points to which it seems necessary to 
 call attention will be touched upon in the remarks on 
 diagnosis. 
 
 Spasm of the individual ocular muscles may occur 
 
 (1) As an cridviicc <if a secotiddri/ deviation in a soaiid 
 ri/e when the other eye, being paretic, is yet used for fixa- 
 tion. 
 
 Thus sup).()Sf thai a i)ati('iit with a paresis of the ri^^ht fXtcnms 
 ncvcrthch'ss fixes with the ri>,'-ht eye l)ecause he sees Itetter with it. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 53 
 
 Then when he looks at some object situated on his right he has to 
 exert an excessive amount of force to turn his tixing eye out suffi- 
 ciently. The same amount of force is, by the law of association, 
 also transmitted to the left internus, and the latter, not being paretic, 
 Avill respond with normal vigor to the excessive stimulus, so as to 
 carry the left eye nnich further to the right than its fellow, and 
 hence quite to the right of the object of fixation. In this case, as 
 the right eye follows the object, and the left eye by an apparently 
 excessive action shoots past it, we might regard the condition as one 
 of veritable spasm of the left internus ; whereas the real state of the 
 case is that the latter muscle is normal and contracts excessively only 
 because the stimulation that it receives is excessive. These cases are 
 therefore correctly denominated as cases of false or apparent spasm. 
 
 (2) In the case of a paralysis of an ocular musle, a spas- 
 tic contraction of one or more of the other inuscks in the 
 same ei/e takes place, by virtue of which, as has been al- 
 ready stated, the deviation becomes more or less concomi- 
 tant and generalized throughout the whole field of fixation. 
 This contraction finally results in a permanent shortening 
 (contracture) of the muscles affected, but before this stage 
 has been reached, a temporary and varying spasm may be 
 set up in the antagonists of the paralyzed muscle, so as to 
 carry the deviation and the diplopia far outside of the field 
 of action of the latter. This was clearly shown in the fol- 
 lowing case which came under my care : 
 
 Paralysis of Inferior Rectus. Varying Spasm of Superior Rectus 
 of same eye. H., male, aged 29. Vertigo, blurring of sight, and 
 diplopia for past two years. No history of syphilis. Presents all the 
 evidences (by inspection, screen, and diplopia tests) of a well-marked 
 paresis of the R. inferior rectus. Vertical diplopia (with image of 
 right eye below = DR) increasing to 6° to 7° (=14" prism) as the 
 eyes are carried down and to the right; diminishing to zero when the 
 gaze was directed down and to the left. Moderate crossed diplopia 
 everywhere; increasing when eyes are directed down and to left. 
 Vertical diplopia of the same character as that found in the lower 
 field prevailed, although to a less extent in the upper field; most 
 marked in looking up and to the right (Eu & r, DR increasing) . This 
 diplopia in the upper field varying much, and partially superable by 
 voluntary effort. 
 
 Here there was evidently a spasm (variable in amount) of the right 
 elevators, and particularly of the right superior rectus (shown by the 
 fact of the vertical diplopia increasing upward and to the rifjhf). 
 The vertical diplopia in the upper part of the field might, it is true, 
 have been due to a paresis of the elevators of the left eye; but the 
 
54 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 variable character of the diplopia and the fact that it was siiperable 
 by voluntary effort negative this supposition. 
 
 (3) Spasm (usually slight) of one or more of the ocular 
 muscles may occur as the result of h-riiotlri^ hsloiis at the 
 base of tJie hrain, particularly meningitis. 
 
 (4) Slight transient spasm may occur in chorea. 
 
 (5) Convulsive tonic spasm may occur in epilepsi/ and Itifs- 
 fen'a, although in these diseases it is not generally the 
 individual muscles that are affected, but the associated 
 movements of the eyes (particularly the parallel move- 
 ments and movements of convergence). Gowers, however 
 (Diseases of the Nervous System), calls attention to a sort 
 of convulsive seizure that maybe styled epileptoid, in which 
 there are suddenly developing tonic and clonic spasms of 
 one or more ocular muscles, associated with more or less 
 obtunding of the consciousness. 
 
 (6) Finally we may have cases of non-pa roxiismal and 
 chronic spai^ni of some one ocular nmsclv, which causes the 
 eye to make an excessive movement as soon as it is turned 
 so that the affected muscle can act upon it. Thus cases 
 have been described in which a spasm of the external rec- 
 tus caused the eye to shoot far outward as soon as the eye 
 was turned past the middle line. Mauthner (Augenmus- 
 kelliihmungen) casts doubt on all such cases, regarding 
 them as probably instances of secondary deviation of a 
 sound eye due to the fact that the other eye is paretic but 
 still performs fixation, so that an excessive impulse is 
 transmitted to both eyes. That is, he would class all such 
 cases under the category of false or apparent spasm (Group 
 1 mentioned above) . But this statement is certainly too 
 sweeping, since cases of chronic spasm, although doubtless 
 rare, do occur, as witness the following that I observed: 
 
 Paralysis of L. Externus; Spasm of L. Inferior Oblique. Ber- 
 tha S., a{?ed 8. Deviation of eyes noticed since birth. Used to h<»kl 
 head to right and does so still wlien looking intently at anything. 
 L. eye eannot move out beyond median line. Wlien eyes are car- 
 ried horizontally to the right, L. eye siiddenlif Jiies itpward and he- 
 cowes buried beneath the upper fid. In associated movements in lower 
 field, L. eye moves normally with the \i. Behind screen L. eye de- 
 viates high up and somewliat in. Deviation of either eye behind 
 .screen about efjual. No double images attainabU'. V. H. -"'4,1: witli 
 +1.00 D. •-•»/:.«. L. 2'7,„. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. oa 
 
 Here the sudden and excessive upward movement of tlie left eye 
 when directed inward could only have been effected by a spasmodic 
 contraction of the inferior oblique; the superior rectus acting but 
 slightly as an elevator when the eye is adducted. 
 
 A similar case in which with paralysis of the R. externus 
 and R. superior rectus there was spasm of the R. superior 
 oblique is the following: 
 
 Emma D., aged 15. Strabismus since scarlatina eleven years \)e- 
 fore. Occasional vertigo; no diplopia. Movements of L. eye nor- 
 mal. R. eye cannot move at all to right, nor upward and to right ; 
 movement upward almost normal when eyes are carried to left (re- 
 tention of power of inferior oblique) ; movement downward excess- 
 ive, especially when eyes are directed to left (excessive action of 
 superior oblique) ; when attempt is made to move eyes straight to 
 left, R. eye shoots obliquely down and to the left (spasmodic action 
 of superior oblique). 
 
 In addition to these cases in which spasm was associated 
 with paralysis, I have seen others in which a deviation 
 limited to one portion of the field of fixation was present, 
 which deviation was always marked but yet varied so irnirh 
 ill amount from one time of observation to another as to 
 necessitate the assumption of its being spasmodic rather 
 than paralytic in origin. 
 
 Symptoms and Differential Diagnosis of the Different 
 Varieties of Muscular Over=action and Under=action. No 
 attempt will be made here to go at all fully into the symp- 
 toms produced by insufficiency or over-action of the indi- 
 vidual muscles. This has already been done in various 
 excellent treatises. I will simply give the following facts 
 to which, as I conceive, too little attention has been paid. 
 
 1. In the deviations considered in the foregoing para- 
 graphs the abnormality, as has been pointed out, may 
 affect either the muscle itself, its tendon, or the nerve and 
 nerve-nucleus supplying it; /. e. the muscle may act above 
 or under the normal either because it is itself too much or 
 too little developed (Structural Deviation) ; or because the 
 direction and insertion of its tendons are not what they 
 should be (Insertional Deviation) ; or because the muscle 
 is in a state of paralysis or spasm (Innervational — Paretic 
 or Spastic — Deviation) . Now it cannot be too strongly 
 insisted upon that tJiese three varieties, however dissiuillar 
 
56 NEW CLASSIFICATION OF MOTOR ANOMALIES, 
 
 hi (>ri(jiii, shoir ill Ijii'ir si/mjifonis inid ohjiriirc siifiis no 
 real point of iUfftn^nct^. Thus weakness of the external 
 rectus, whether arising from feeble and arrested develop- 
 ment of the muscular fibre, or from mal -position of the 
 tendon (natural or produced by a tenotomy), or from lesion 
 of the sixth nerve, gives rise to the same symptoms and 
 offers the same appearances to objective examination. 
 The characters of the paretic and spastic deviations, to 
 be sure, are generally more definite and more striking 
 than are those of the other anomalies mentioned, but 
 this is simply owing to the fact that such cases are 
 -usually seen early, before any compensatory changes 
 have taken place and while the diplopia, false projection, 
 vertigo, and other symptoms are therefore still marked. 
 Precisely the same effect will be produced in a patient with 
 binocular single vision if one of the tendons is completely 
 divided. And in cases of long standing— particularly in 
 congenital cases — it is impossible to say with certainty 
 from the symptoms alone without reference to the history 
 whether faulty innervation, faulty insertion, or faulty 
 structure lies at the basis of the anomaly. 
 
 2. Couiieniial (Ji^viafioiis present several peculiarities. 
 In the first place they cause little or no trouble for the ob- 
 vious reason that the patient from his infancy has learned 
 to adjust himself to the anomalous condition present. 
 Again, it is remarkable that, even after the condition has 
 existed for years, there is no constant suppression of the 
 diplopia such as occurs in comitant squint, and further- 
 more, there is no tendency, as in the case of other non- 
 comitant deviations, to a transformation into a comitant 
 deviation by the development of a contracture of the an- 
 tagonists. The reason probably is that as the patient has 
 never known any different condition from that which he 
 was born with, and as this condition consequently is the 
 natural one for him, he experiences no inconvenience from 
 its continuance, so that no involuntary tendency is set up 
 toward its rectification. The result is' that these congenital 
 deviations, which may be due cither to paresis or to a struc- 
 tural defect, afford, as far as objective signs go, the 
 most typical picture of uncomplicated muscular paralysis 
 that we can have. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 57 
 
 3, Ac<iuhT<1 iitKsciiIar (leviafioas, on the other hand, 
 whether due to anomalies of innervation or insertion, al- 
 ways tend to become comltanf ; this being affected by a 
 gradually developing contracture of the antagonists when 
 the affected muscle is too weak, and by a weakening of 
 the antagonists when the affected muscle is too strong. 
 It is thus, probably, that many cases of comitant strabis- 
 mus convergens and strabismus divergens are produced ; 
 and the few cases of strabismus sursumvergens that I have 
 met with were apparently all developed in this way. 
 
 Thus paralysis of the R. elevators, when not of congenital origin, 
 is regularly followed by spasm of the R. depressors, causing the 
 right eye to stand lower than the other in all portions of the field 
 of fixation. This process continuing and the spasm developing into 
 a confirmed contracture, the difference in height between the two 
 eyes (L. hypertropia) becomes equal for all directions of the gaze; 
 the limitation of movement of the right eye upward is compensated 
 for by a corresponding increase in its movements downward: and 
 the picture of a typical comitant strabismus deorsumirrffens is pro- 
 duced. 
 
 If but one of the elevators, e. g. the superior rectus, is paretic the 
 spasm is apt to be confined, in the first instance at least, to the cor- 
 responding depressor, /. e. the inferior rectus. In this case the devi- 
 ation will become half-comitant, that is, comitant for movements up 
 and down but not for lateral movements. Thus, if the right supe- 
 rior rectus were the paretic muscle, we should have first a L. hyper- 
 phoria, very marked in the upper right-hand quadrant of the field of 
 fixation and diminishing rapidly, both when the eyes were carried 
 down and when they were carried to the left. Later, when spasm of 
 the right inferior rectus had developed, the L hyperphoria would 
 become pronounced in the lower right-hand quadrant also, and ulti- 
 mately so much so that whether the eyes were carried up or down, 
 the right eye would always stand about the same distance below the 
 left. But in both the upper and lower portions of the field the L. 
 hyperphoria) would still increase as the eyes were carried to the right 
 and diminish to zero as they were carried to the left; so that even 
 under these circumstances the deviation would not be comitant for 
 lateral movements. 
 
 A case of this sort, in which the inferior rectus was the muscle 
 primarily affected and in which semi-comitancy was being developed 
 by spasmodic action of the superior rectus has already been men- 
 tioned (under the head of Spasm of the Ocular Muscles). 
 
 Cases in which a comitant (and even an alternating) lateral squint 
 has developed out of a paresis of the externus. folloAved by contract- 
 ure of the internus and later by partial restoration of the power of 
 
58 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 the externus, have been repoi-ted by Spieer ("Rt)yal London Ophth. 
 Hosp. Reports," xiv. 1, 18J)o), I liave observed analogous cases, 
 ])arti('ularly <>iie in which a partial oculomotor paralysis with second- 
 ary contracture of the externus had resulted in a nearly coniitant 
 strabismus divergens. 
 
 In proportion as the deviation becomes transformed from 
 a non-oomitant to a comitant one, the symptoms grow less 
 disturbing; for, as already stated, it is always the case 
 that, other things being equal, a comitant deviation will 
 give less trouble than will one that is non -comitant. 
 
 4. The ilia(iii(>sis Intween ocer-adiou and Hn<Jer-<(rii<>n is 
 often difficult. Theoretically, over-action (spasm) is asso- 
 ciated with excessive movement, and under-action (pare- 
 sis) with very deficient movement in some one direction. 
 But, unless the paralysis is nearly total or the spasm is 
 great, it is not always easy to say whether it is the muscle 
 of one eye that is under-acting or whether it is the asso- 
 ciated antagonist of the other eye that is over-acting; and 
 when secondary changes have taken place, transforming 
 the deviation into a comitant one, the diagnosis is often 
 impossible. 
 
 Before this has occurred the differentiation may be made 
 from the following considerations. 
 
 OVKR-ACTIOX. I INDKK-ACTIUN. 
 
 Points in Common. 
 One eye moves faster and further than the other \vhen both are 
 carried in some one particular direction: and this discrepancy be- 
 tween the position of the eyes and also the diplopia, false projec- 
 tion, and vertigo become more and more pronounced, the further the 
 eyes are carried in tliat direction. The primary i)ositi(.n for both 
 eyes is nearly the sanu-. 
 
 The absolute excursion of the 
 faster moving eye in the given 
 direction is greater than normal; 
 that of the other eye is normal. 
 
 The total excursion of the fast- 
 er moving eye in the given direc- 
 tion and in its opposite is greater 
 than normal: /. <., the field <)f 
 fixation is excessively large in one 
 of its diameters. 
 
 Fixation is usually perfornu'd 
 l)y the slower moving eye. 
 
 The amount of deviation may 
 show gr«'at and sudden changes 
 fr()m time to time. 
 
 The al)solute I'xcursion of the 
 faster moving eye is n()nnal in all 
 directions: that of the other eye 
 is subnormal. 
 
 The total excursion of the fast- 
 er moving I'ye is normal, that of 
 the other eve is subnormal; /. c, 
 the field of fi.xation of the latter 
 is contracted in one of its diame- 
 ters. 
 
 Fixation usually performed by 
 the faster moving eyi'. 
 
 The amount of deviation re- 
 mains constant or changes slowly 
 aiul pi'ogressiveiy. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 59 
 
 5. While the diagnosis of a marked underaction of one of 
 the ocular muscles usually presents no difficulty, there is 
 quite a large number of cases in which the condition is not 
 so obvious, the weakness of the nuiseles beiiiy eoinpavatively 
 sjiqhf.* In these cases diplopia does not occur until the 
 eyes are removed some distance (10" to 20°) from the pri- 
 mary position. As soon as it does appear, however, it 
 develops in a perfectly typical fashion, showing marked 
 increase in some one special direction and diminishing 
 elsewhere to zero. Most cases of this sort of anomaly, that 
 I have observed, have been those in which there was a 
 pretty pronounced weakness (perhaps of congenital 
 origin or, rather, due to non-development) of the superior 
 rectus ; less frequently the inferior rectus seemed involved. 
 The nature and course of these cases have not been thor- 
 oughly investigated, but it is noticeable that they are 
 frequently associated with a convergence -insufficiency 
 which shows a tendency to go over into a divergence - 
 excess, resulting, in sone instances at least, in a regular 
 divergent squint. The chief symptoms (which, however, 
 are, very likely, attributable to the convergence-insuffi- 
 ciency) are conjunctival irritation, asthenopia (often very 
 marked), headache, and diplopia. In many cases the 
 symptoms are insignificant and this fact ' coupled with the 
 absence of diplopia in the primary position is probably the 
 reason why these cases have been left uninvestigated. 
 Quite a number of cases of hyperphoria doubtless belong 
 to this category. 
 
 Another variety of muscular weakness, transitory in its 
 character, is that already referred to as associated with 
 neurastJienia. Here we may find diplopia all round the 
 periphery of the field of fixation, i. e. within 35° of the 
 primary position (Concentric contraction of the field of 
 binocular single vision). This condition would appear to 
 have little significance except as a diagnostic sign of the 
 condition with which it is associated. 
 
 It is not unlikely that slight degrees of muscular sjjasm 
 are at the bottom of some of the cases of heterophoria that 
 we meet with; e. </. spasm of either one of the elevators 
 
 *It is to these cases that the old term muscularlinsufficiency should be limited. 
 
60 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 or of either one of the depressors may occasion a hyper- 
 phoria of more or less varying character (Spastic lietero- 
 phoria). I have notes of five or six cases in which the 
 presence of a varying and even alternating hyperphoria 
 seemed to be due to more or less spasmodic contraction of 
 the vertical muscles. 
 
 Finally it is quite likely that a large number of cases of 
 slight deviation are due to moderate nnder'arttoii of one 
 muscle conihhied in'th orer-action (secondary spasm) of 
 another, so as to produce a more or less comitant deflec- 
 tion. Probably most of the cases of hyperphoria, in 
 which the deviation, although moderate in amount, is 
 present through the whole field of fixation, are attributable 
 to combined anomalies of this sort (comitant hyperpliona ). 
 Cases of this kind often give rise to asthenopia, headache, 
 neuralgia, and sometimes to gastric disturbance and im- 
 pairment of nutrition. Diplopia is infrequent and when 
 present can usually be readily overcome. 
 
 6. The diagnosis of the muscles affected in a case of 
 paralysis or spasm is readily accomplislit^d hji means of the 
 donhh' imaijes if the following principles are kept in mind. 
 
 (a) The diplopia increases progressively as the eyes are 
 carried in that direction in which the action of the muscle 
 affected is normally most pronounced. 
 
 (b) Paralysis of any given muscle of one eye produces 
 diplopia of the same character and increasing in the same 
 way as does a spasm of the associated antagonist in the 
 other eye. 
 
 (c) While paresis or spasm of one of the vertical mus- 
 cles does produce lateral diplopia, this diplopia maybe and 
 often is neutralized by the existence of other factors, so 
 that it is of no practical significance in the diagnosis. 
 The latter must rest solely upon the difference in height of 
 the double images and the portion of the field where this 
 difference is most pronounced. 
 
 This fact, emuiciatt'd and explained very elearly by Mauthner, is 
 frequently overlooked, many insistiuK that paresis of the superior 
 and inferior recti must produce crossed, and paresis of the obliques 
 homonymous diplopia. But, apart from the fact that these pareses 
 are often asso<'iated with cxophoria or esoplioria of sufficient 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 61 
 
 amount to neutralize their lateral diplopia, the natural tendency 
 which the visual axes display to diverge when the eyes are directed 
 up and to converge when they are directed down will work to aljro- 
 gate the homonymous diplopia due to a paresis of the inferior oblique 
 and the crossed diplopia due to a paresis of the inferior rectus. As 
 a matter of fact I have found paresis of the superior and inferior 
 recti often associated wdth homonymous diplopia. 
 
 The following table, constructed in accordance with the 
 three principles just enunciated, shows succinctly the way 
 in which the diagnosis can be made from the double 
 images. 
 
 DIAGNOSTIC TABLE 
 
 of Faralysis and Spasm of the Ocular Muscles. 
 
 Note, DII = homonymous diplopia; DX = crossed diplopia; DR. 
 = vertical diplopia with the image formed by the right eye below ; 
 DL = vertical diplopia with the image formed by the left eye be- 
 low. Eu, Ed, Er, El, Eu & r, etc., = associated parallel move- 
 ments in which the eyes are directed respectively up (Eyes up) 
 down, right, left, up and right, etc. >> = increasing; << = de- 
 creasing. 
 
 Diplopia 
 
 = Paresis of 
 
 OR = Spasm of 
 
 Er. DII >> greatly. 
 
 R. E'i;ternal Rectus 
 
 L. Internal Rectus 
 
 Er. DX 
 
 L. Internal Rectus 
 
 R. External Rectus 
 
 El. DII 
 
 L. External Rectus 
 
 R. Internal Rectus 
 
 El. DX 
 
 R. Internal Rectus 
 
 L. External Rectus 
 
 Eu. &r. DL " 
 
 R. Superior Rectus 
 
 L Inferior Oblique 
 
 Eu. &r. DR ■' 
 
 L. Inferior Oblique 
 
 R. Superior Rectus 
 
 Eu. &1. DR " 
 
 L. Superior Rectus 
 
 R. Inferior Oblique 
 
 Eu. &1. DL " 
 
 R. Inferior Oblique 
 
 L. Superior Rectus 
 
 Ed. &r. DR " 
 
 R. Inferior Rectus 
 
 L- Superior Oblique 
 
 Ed. & r. DL " 
 
 L. Superior Oblique 
 
 R. Inferior Rectus 
 
 Ed. &1 DR " 
 
 R. Superior Oblique 
 
 L. Inferior Rectus 
 
 Ed. &1. DL '• 
 
 L. Inferior Rectus 
 
 R. Superior Oblique 
 
 The above table is sufficient for all ordinary working 
 purposes, but or the sake of coi-ppleteness I grve also the 
 more extensive one subjoined, which I have devised to 
 show how the character of the diplopia may be modified 
 by circumstances. 
 
62 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 TABLE OF DIPLOPIA. 
 
 A. HOMOXYMOrs DIPLOPIA VARYIN(t WITH DIFKKKKNT DIRKCTIONS 
 OF THE UAZK. 
 
 /. Vtiridtion f/reat = Paresis of Externus (Sjkisiii of Internns.) 
 
 CHARACTER OF DIPLOPIA 
 
 INDICATES PARESIS 
 OF 
 
 OR SPASM OF 
 
 DII >> in Er, << in El. 
 DII » in El. << in Er. 
 
 R. External Rectus 
 L. External Rectus 
 
 L. Internal Rectus 
 R. Internal Rectus 
 
 II. Variation slifjht = Paresis of Oblique (Spasm of Sii])erior or In ft 
 
 rior Bectus) or a couiitant esojthoria <(ssociate<l irifli a conditio)) 
 
 'caiisinf/ rarijiiuj 1)X. 
 
 f Particularlv marked in! ( R. Inferior Oblique 
 niT > > in Vr I K"- iKu. & r.] I R. Superior Rectui 
 
 uii <"r- 111 r,r. i Particularly marked in I R. Superior Obliqi 
 
 I Ed. [Ed. & r.l i R. Inferior Rectus 
 
 f Particularly marked it 
 . , „, J Eu. [Eu. & l.J 
 "' • I Particularly marked ir 
 Ed. [Ed. &1.J 
 
 f L. Inferior Oblique 
 "I L. Superior Rectus 
 J L. Superior Oblique 
 1 L. Inferior Rectus 
 
 L. Superior Rectus 
 L- Inferior Oblique 
 L. Inferior Rectus 
 I,. Superior Oblique 
 
 R. Superior Rectus 
 R. Inferior Oblique 
 R. Inferior Rectus 
 R. Superior Oblique 
 
 B. CROSSED DIPLOPIA VARYINU IN DIFFERKXT DIRECTIONS OF 
 THE (iAZE. 
 
 I. Variation great = Paresis of Internns (S/iasni of IJ.rternas.) 
 
 CHARACTER OF DIPLOPIA 
 
 DX>> in Er., << \r\ El. 
 D>> in l-:i.. << in Er. 
 
 = PARESIS OF 
 
 OR SPASM OF 
 
 L. Internal Rectus R. External Rectus 
 R. Internal Rectus I,. External Rectus 
 
 //. Vari<ttioii sliijlit = Paresis of a Superior or Inferior Pectus (S))t(^ 
 of an Ohlii/iw) or a comitant e.vophoria associated with a 
 condition causing rarijinn DII. 
 
 I I'arlicularly marked inl I I,. Superior Rectus I K. Inferior Oblique 
 
 UX >> n Er. ', Eu. lEu. & r.) I L. Superior Obliciue I K. Superior kectusi 
 
 << in El. 1 Particularly marked in \ I,. Inferior Rectus I K. Superior Oblique 
 
 I Ed. Ed. it r.l ( I,. Superior (>bli(|i:e K. Inferior Rectus 
 
 ( Particularly marked in ( R. Superior Rectus L- Inferior Oblique 
 
 n.\ >> in I-;i. J V.u [Eu. &1.1 1 K. Inferior Oblique U. Superior Rectus 
 
 <'1inEr. 1 Particularly marked in f R. Ir ferior Rectus I.. Superior t)blique 
 
 I E<1. [I'M. & l.j I K. Superior Obli(|Ue I,. Inferior Rectus 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 63 
 
 C. VERTICAL PTPLOPIA VARYING IN DIFFERENT DIRECTIONS OF THE 
 GAZE (= PARESIS OR SPASM OP ELEVATOR OR DEPRESSOR.) 
 
 1. Diplopia ^^ in Eii. (Paresis or Spasm of Elerator.) 
 
 CHARACTER OF DIPLOPIA 
 
 1DR. most marked in Eu. 
 & r. I regularly associ- 
 ated with DII >> iu 
 DR. most marked in Eu. 
 & 1. [regularly associ- 
 I ated with DX > > in 
 I Eu. & r.] I 
 
 PARESIS OF 
 
 OK SPASM OK 
 
 I,. Inferior Oblique R. Superior Rectus 
 
 1 
 L. Superior Rectus R. Inferior Oblique 
 
 f DL most marked in Eu. I R. Superior Rectus L, Inferior Oblique 
 1 & r. [regularly associ" 
 
 I ated with DX > 
 ,^, , .... 1 Ru. &1.] 
 Y>h, K- K- in hA\. -^ jjj^ j^Qg^ marked in Eu. 
 
 I & 1. [regularly associ- 
 
 I ated with DII > > in 
 
 I Eu. &r.] 
 
 R. Inferior Oblique L. Superior Rectus 
 
 II. Diplopia U^ in Ed. (= Paresis or Spasm of Depressor). 
 
 !DR most marked in Ed. I R. Inferior Rectus ^I.. Superior Oblique 
 & r. [regularly associ-] 
 ated with DX >> in 1 
 
 DR most marked in Ed.j R. Superior Oblique L. Inferior Rectus 
 1 & 1. regularly associat-' ' 
 
 ed with DII >> in Ed.i 
 I &r.] 1 
 
 [ DL most marked in Ed. L. Superior Oblique R. Inferior Rectus 
 1 -& r. [regularly associ-' 
 I ated with DII > > in 
 
 DI, > > in Ed | p^ niost marked in Ed.' L. Inferior Rectus R. Superior Oblique 
 I & 1. regular associated 
 I with DX>>inEd. & r. 
 
 From the foregoing table the following facts are appar- 
 ent: 
 
 (1) All Jiomonyinous diplopia, whether laiye or .'<niaU, 
 irhich increases as the eyes are carried to the right indicates 
 niider'action of SOME muscle of the ru/ht ei/e or over-nrtioii 
 of SOME muscle of the left. 
 
 (2) A crossed diplopia which increases as the ei/es are car- 
 ried to the right indicates nnder-action of SOME muscle of 
 fJi(^ left e//e or ovcr-acfion o/" some muscle of the rhjht. 
 
 Treatment of Anomalies of the Individual Muscles. 1. In 
 every case of over-action or under-action of the muscles 
 our first attempts must be directed to removing the cause of 
 
64 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 the trouble. This is effected with more or less success in 
 syphilitic paralysis and in the paralysis caused by the 
 pressure of meningitic effusions upon the nerves when we 
 employ the iodides and mercury; in the so-called rheu- 
 matic paralysis, due apparently to exposure to cold, when 
 we use sodium salicylate and the iodides; and when in 
 hysterical disorders we employ the appropriate moral 
 treatment. 
 
 2. When the cause is unknown or cannot be reached, an 
 (xpecfant treatment combined with corroborrnif ineasiins 
 (especially open-air exercise) must be employed. This is 
 particularly the course to be pursued in spastic deviations, 
 in hysterical and diphtheritic paralysis, and in the limita- 
 tion of the movements of the eye due to neurasthenia. 
 
 The use of strychnine, advocated by some as bein^ a direct tonic 
 for insufficient muscles, seems to be efficient only so far as it acts to 
 iinprove the patient's general condition. The same may be said of 
 I'lectricity. 
 
 3. When the deflection is slight, confirmed, and espe- 
 cially if it is more or less comitant, prisutK often do good 
 service, particularly in the vertical deviations. 
 
 In the lateral deviations they are of less service, because these are 
 frequently complicated by the presence of divergence or convergence 
 anomalies, in which tlie prolonged use of prisms is distinctly injur- 
 
 ious. 
 
 4. Operaiive nica.sures are to be adopted only when we 
 are assured that the condition has reached a stage in which 
 it is no longer likely to undergo change. Even in long- 
 standing cases of paralysis it may be dangerous to oper- 
 ate, since the paralysis may disappear even after lasting 
 for months, and then the operation which previously suf- 
 ficed to correct the deviation will now over-correct or pro- 
 duce a deviation in the opposite sense which may be worse 
 than the original one. 
 
 On the other hand, the judicious division of a contractured unpar- 
 alyzed nuisde may by giving the paraly/.«'d muscK» more play assist 
 in restoring tlie power in tlie latter. See two case's l)y Chi'vaHercau 
 (Trans, of Vlll. Internat. Ophth. Congress, Edinburgli, 1H!»4) in 
 which the movements of an eye the subject of a partial oculomotor 
 paralysis were restored by tenotomy of the unparalyzi'd extenuis. 
 These cases are analogous to those iji whicli the power of the extend, 
 weakened l.y p.-rsistenl .M.iilracliire of interni due to a .•onvergence- 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 65 
 
 spasm, is gradually restored by the very prolonged use of the propei- 
 correcting glasses which relieve the spasm and allow the extern! to 
 act more freely. (See Long and Barret's eases, cited in section 
 YII.) 
 
 In any case care must be taken that the app)'<ypriate op- 
 eration is performed. The principles of operating, which 
 were admirably enunciated by A. Graefe, may be thus 
 stated : 
 
 Over-acfion of a muscle is to be relieved by tenotomy of 
 the over-acting muscle. JJnder-action is to be relieved by 
 tenotomy of the associated antagonist to the under- acting 
 muscle, or, where this is impracticable, by advancement of 
 the under-acting muscle itself. Sometimes, especially in 
 paralysis of the externus and internus, these operations 
 have to be further reinforced by tenotomy of the direct an- 
 tagonist of the paralyzed muscle. 
 
 The reason for these rules is obvious. When a muscle is too strong 
 we can reduce its action more or less effectively by a tenotomy. If 
 the muscle is too weak, but yet retains some of its power, we can 
 increase this power by performing an advancement. If, however, 
 the muscle has lost all power, an advancement is obviously futile, 
 and if the muscle acts biit little an advancement alone is generally 
 insufficient. Then we have only to remember that when a muscle is 
 too weak, the effect upon the movements of the two eyes is the same 
 as if the associated antagonist in the other eye was too strong; and 
 if we tenotomize this antagonist, we shall limit the movement of the 
 sound eye in the same sense and to the same extent as that in which 
 the movement of the affected eye is already limited, /. e. both ej-es 
 will again move equally with each other, although the movement of 
 neither will be normal. If no secondary changes have taken place, 
 tenotomy of the associated antagonist alone may suffice, but usually 
 the weakened muscle is opposed by a contractured and hence over- 
 acting mviscle in the same eye (direct antagonist), and therefore we 
 may have also to divide the latter in order to secure the proper bal- 
 ance of action. 
 
 For the particular cases these rules may be expanded as 
 follows : 
 
 Under-actlon of the B. externus indicates tenotomy of the 
 L. internus, usually combined with advancement of the R. 
 externus and often with tenotomy of the R. internus. 
 
 Under-aetion of t lie li. in teriiu.s requires advancement of 
 the R. internus combined with tenotomy of both externi. 
 
 The advancement in this case is imperatively demanded, because 
 the internus has to be used in conA'ergence as well as in associated 
 5 
 
66 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 imrallel moveinent.s. For the latter it might aet .suffieieiitlv well, eevn 
 if intrinsically weak, provided the externiis of the other eye was also 
 weakened and to the same extent: but for the proper performance 
 of eonvergrence movements the interniis reiiuires to he intrinsically 
 strong:, which can be effected only by an advancement, 
 
 Vnder-action of the H. superior ohlique requires tenotomy 
 of L. inferior rectus. This operation gives very satisfac- 
 tory results. 
 
 Under-avtion of the R. inferior oblique ve(\\i\pes, tenotomy 
 of the L. superior rectus. 
 
 Under-avtion of tJie R. superior rectus is in general best 
 remedied by advancement of the muscle itself. If there is 
 secondary contracture of the inferior rectus, the latter may 
 be divided also, but this operation should be performed 
 with considerable caution owing to the unpleasant effects 
 produced by insufficiency of any one of the depressor 
 muscles. 
 
 In very slig:ht cases of insufficiency of the superior rectus in which 
 the increase of the diplopia in lateral directions of the gaze would 
 not be very great, and in which the aim is simply to remove the mod- 
 erate hyperphoria in looking straight ahead, cautious tenotomy of the 
 siiperior rectus of the other eye may replace the operation of ad- 
 vancement. 
 
 Lender-action of the R. inferior rectus requires advance- 
 ment of the muscle itself, which may need to be supple- 
 mented by tenotomy of the R. superior rectus. 
 
 Over-action of eitJier one of the four recti is remedied by 
 advancement of the over-acting muscle. 
 
 Over-action of the R. superior oblique calls for advance- 
 ment of the L. inferior rectus. In very slight cases this 
 operation may be replaced by a cautious tenotomy of the 
 R. inferior rectus. 
 
 Over-action of the R. inferior oblique is relieved by ad- 
 vancement of the L. superior rectus or, in very slight cases, 
 tenotomy of the R. superior rectus. 
 
 It is probably from a failure to conform to these principles that a 
 large pai't of the disappointment occasioned by the results of tenoto- 
 mies done for lieterophoria is due. For example, a L. hyperphoria 
 due to insuthciency of a R. elevator nuisde is treated by tenoto- 
 mizing the R. inferior rectus. This operation does not essentially 
 relieve the litiiitation of movenu-nt in the upper Held, which really 
 caused the hyperphoria and niost likely the symptoms ascribed to the 
 latter; on the coiitrarv, it adds to tli<' condition already (>xisting a 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 67 
 
 new and very troublesome patliolof^ical eoiidition, namely, a limita- 
 tion of the movements of the right eye in the lower tield also. In 
 other words, to the paresis already present another paresis has been 
 added l)y oi)eration, and the patient suffei's from the eoml)ined effects 
 of l)oth. That the «^ffeet of both pareses actually eo-exist can readily 
 be demonstrated by an examination of the double images. It will be 
 found that the diplopia in the upper field has not been materially re- 
 duced by the operation, while a diplopia which did not exist l)efore 
 has been introduced into the lower field and gives rise to nnich dis- 
 turbance. In this case advancement of the weak elevator in the af- 
 fected eye or tenotomy of the elevator in the other eye would be the 
 proper operation. 
 
 Parakineses. Tremor of Individual Ocular Muscles (Uni= 
 lateral or Non=symmetrical Nystagmus). The tremulous 
 movement (alternating spasm) that we denote by the name 
 of nystagmus, although usually affecting equally the asso- 
 ciated muscles in the two eyes, and therefore dependent in 
 all probability upon a lesion of the association-centers, may 
 be confined to the muscles of one eye or be of a different 
 character in one eye from that in the other. 
 
 Hence, while ordinarily constituting a perversion of the 
 associated parallel movements of the eyes, in these cases 
 it must be regarded as a perversion of the movements of the 
 individual muscles. These cases, are, to be sure, quite 
 rare. Graefe (Graefe-Saemisch) reports four cases of uni-^ 
 lateral vertical nystagmus (two observed by himself) , and 
 adds that, while he has seen cases of slight rotary nystag- 
 mus confined to one eye, he has never met with one of uni- 
 lateral horizontal nystagmus. Frost, however (Trans. 
 Ophth. Soc. of United Kingdom, xiv. 245), reports a case 
 of acquired nystagmus in which the oscillations were hori- 
 zontal in one eye and vertical and rotary in the other. 
 
 VI. 
 
 ANOMALIES OF ASSOCIATED PARALLEL MOVEMENTS. 
 
 Hypokineses. Paresis and Insufficiency of Associated 
 Parallel flovements. rarali/si.s of the lafemJ associated 
 iiioccinrnts of the eyes is not infrequent in destructive cer- 
 ebral disease, particularly apoplexy, the site of the lesion 
 in paralysis of dextroversion being in the left, and in par- 
 
68 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 alysis of sinistroversion in the right half of the brain. In 
 pure cases of this sort the power of convergence is re- 
 tained, showing- that the internal rectus, although incapaci- 
 tated as far as consentaneous action with the opposite 
 externus is concerned, is not disabled from performing 
 work in conjunction with its fellow internus. This shows 
 that in these cases we are not dealing with a conjoined 
 paralysis of one externus and one internus, but with an 
 inhibition of one particular hioreiiioii of the two eyes. 
 
 Parabisix of sursmiivermon (without any involvement of 
 the lateral movements) and para/ >/.s/,^ of .sursta/iverKt'oii a)i(( 
 deorsumi'ersion (of/efher have been observed (Gowers; 
 Sauvineau, Trans, of VIII. Ophth. Congress, Edinburgh, 
 1894) . 
 
 Except as diagnostic signs of the condition causing them 
 these associated deviations are of little clinical importance. 
 Whether there are slighter grades of these disorders, not 
 dependent upon severe structural disease and possibly 
 productive of more symptoms on their own account, has 
 not, as far as I know, been positively demonstrated. 
 
 Certain cases, however, described by Savag-e (Oph. Record. 
 Jan., 1896) under the name of Asthenic vertical orthophoria 
 in which the combined up-and-down movements of botli eyes 
 (sursum version and deorsum version) were performed insuffi- 
 ciently and with difficulty wouUl seem to belong' in tliis cate- 
 gory; and possibly the explanation of the conditions called by 
 Stevens Anatropia and Catatropia nuiy l)e had by assuming a 
 weakness of deorsumversion in the former case and of sursumversion 
 in the latter, so that in either instance both visual lines are- off tlie 
 proper level (see Section IX). 
 
 Hyperkinesis. Spasm of Associated Parallel riovements. 
 Spasm of the associated lateral movements producing 
 deviation of both eyes to the right (Spastic dextroversion) 
 or to the left (Spastic sinistroversion) is not infrequently 
 observed as the result of irritative lesions of the brain. 
 Deviation to the right is produced by disease of the left 
 side of the brain and vice vrrsa. 
 
 Spasm of associated movements (particularly, combined 
 vertical and lateral spasm, producing oblique deflections 
 of both visual lines) also occurs as a transient and par- 
 oxysmal manifestation in epilepsy and hysteria. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 69 
 
 Tlie fuvious case described by Frost (Trans. Ophtli. Soc. United 
 Kingdom), in which there was spastic deviation of both eyes down 
 and to the right, but in which there Avas no actual impairment of the 
 movements of either eye by itself, was apparently hysterical in 
 character. 
 
 The following peculiar case of a/fernafing spasm of asso- 
 rlafed parallel movements was apparently choreiform in 
 character and would seem to form a sort of connecting 
 link between cases of tonic spasm, such as those just men- 
 tioned, and true nystagmus. 
 
 Ghoreiform Spasm of Associated Oblique Movements. 
 Simon N., aged 13 years, came under my care Nov. 1*2. 1S92. 
 Chorea two years ago. Anemic. Now shows every few minutes, 
 especially when watched, sudden darting movements of both eyes 
 upward and to the right and back again. The return movement 
 takes place in two phases, the eyes shooting down and to the left 
 somewhat beyond the primary position, and then by a sharp jerky 
 motion coming up again to the latter. If the gaze is directed to the 
 left, both eyes dart upward and to the left and then back again. In 
 either case, whether moving up and to the right or up and to the 
 left, the direction of the movement is at an angle of 4.5° with the 
 horizontal, and the eyes are carried up until the pupils are three- 
 quarters buried beneath the upper lids. Slight choreiform twitchings 
 of the face accompany the movements. 
 
 Orthophoria. No diplopia. Associated movements, although slug- 
 gish, perfectly normal. 
 
 V. R. 'Vi.-. L- 'Vto. Under liomatropine. R. + 1.00 D. '■/,,: L. 
 + 1.50 D. Cyl. Ax. 85° T. '"7:>o. 
 
 Three weeks treatment with arsenic and hydrochloric ac-id effected 
 no improvement. On Jan. 15, 18U3, R. + 0. 75 D. Sph., L. + 1.50 
 I). Cyl. Ax. 85° T. given. Patient then passed from observation and 
 has not been seen since. 
 
 Except for the long interval l)etween the separate spasmodic 
 movements, the appearances presented in this case differ in no re- 
 spect from those observed in nystagmus. Its development, however, 
 in a patient with fair sight and normal muscles, and the past history 
 and present evidences of chorea led me to regard it not as a true 
 nystagmus. If nystagnnis at all, it was a very rare form of the 
 affection. 
 
 Parakineses. Tremor of Associated Parallel Movements 
 (Nystagmus). Nystagmus, as ordinarily met with, con- 
 sists of an equal and parallel movement of the two eyes, 
 both executing a series of rapid oscillations in the same 
 direction and at the same time. These oscillations, which 
 vary in frequency from 30 to 150 a minute, occur in two 
 
70 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 phases, a rapid darting movement first taking place in a 
 certain direction and this being followed by a movement 
 of return to and beyond the original position of the eyes. 
 The latter or second phase, although slower than the first, 
 is evidently an active movement and not a mere relaxation 
 of the muscles that have just been spasmodically con- 
 tracted. The direction of the movement is usually from 
 side to side ( Jforizonfal iii/sfagnius), sometimes rotary, 
 both vertical meridians revolving in the same direction 
 (Rotary nysfar/)ni(t< ), and very rarely vertical ( Vertical 
 ni/star/mus). Not infrequently combinations of two, or 
 even of all three forms are observed (Mixed iit/sfaj/nitis). 
 
 Movements of this character point to a pathological con- 
 dition of the association-centres, causing the discharge of 
 alternate and excessive stimuH from the latter instead of 
 the simultaneous and equal stimuli of moderate intensity, 
 which enable the normal eye to remain steady in the posi- 
 tion of fixation. 
 
 The eyes ordinarily, when looking at an object strai^lit aliead of 
 them, are kept in place by simultaneous contraction of the opposing- 
 muscles; i. e. they move neither to the right nor to the left, bec:iuse 
 they receive equal and simultaneous impulses from the cen- 
 tre for right-handed movements (dextroversion) and that for left- 
 handed movements (sinistroversion). 
 
 If, however, these impulses, instead of being simultaneous, are al- 
 ternate, so that the eyes first receive an impulse from the centre for 
 dextroversion a)ul then one from the centre for sinistroversion, and 
 if these impulses allcniate rapidly, we sliall have the picture of hori- 
 zontal nystagmus. 
 
 A similar want of simultaneity in the dischai'ge of impulses from 
 the centres for sursumversionand (kM)rsumversion will produce a rer- 
 timl nystagmus. And a rotari/ nystagnnis will result from tiu' tlis- 
 charge'of alternate instead of simultani'ous stinudi from the centres* 
 which produce rotati<m of both vertical meridians to the right and to 
 the left respectively. Finally, a combniation of some or all of these 
 anomalies accounts for tlie various forms of iiiixed nystagmus. 
 
 This conception of the central orif/in of nystagmus, and 
 more particularly of its origin from some lesion of the dif- 
 ferent association -centres, seems forced upon us, not only 
 
 ♦Inferred to exist from this very symptom. The riKht-rotatinK ceutre, nctiiiK by 
 itself, would proilme simultaneous contraction of the riRht inferior oblique and in- 
 ferior rectus and of the left superior oblique and superior rectus: and the left-rotat- 
 injf centre would similarly produce contraction of both inferior muscles ol tlie lelt 
 and both superior muscles of the right eye. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 71 
 
 by the character of the movements executed, but also by a 
 great variety of pathological data. For further informa- 
 tion as to the latter, reference may be made to the exhaust- 
 ive articles by Graefe (Graefe-Saemisch and Arch, fiir 
 Ophth., xxiv. 3, 1895). 
 
 VII. 
 
 ANOMALIES OF CONVERGENCE. 
 
 Hypokineses. Paralysis and Insufficiency of Convergence. 
 
 Absolute loss of power of convergence with retention of the 
 power of making associated parallel movements has been 
 occasionally observed. Since either eye can still be turned 
 inward when acting with its fellow to move to the right or 
 to the left, these cases cannot be referred to paralysis of 
 the interni, but indicate some lesion of the convergence- 
 centre, causing a paralysis of convergence ( PavalJeJ sqw'nf 
 of Schneller) . 
 
 Cases of this sort in which the paralysis was total or 
 practically so (convergence near-point at from 2 to 6 
 metres), have been described as well as others in which 
 the paralysis was marked but not complete. I myself have 
 seen one case of the sort. 
 
 The paralysis is frequently associated with paralysis of 
 accommodation and in some of Parinaud'sand Sauvineau's 
 cases was accompanied by paralysis of sursumversion 
 and deorsumversion. One peculiar feature is that the 
 prism-convergence (/. e. the power of overcoming prisms, 
 base out) is retained in some of the cases (Straub). 
 
 The eases hitherto reported are : 
 
 Schweigger, Klin. Untersiich, iiber das Schielen 1881 (cited by 
 Straub) 2 cases. 
 
 Parinaud, Arch, de Neurologie, 1883 (cited by Sauviueau). 
 
 Sales, Trans. Ophth. Soe. United Kingdom, iv. (1884), p. 390 (cited 
 by Gowers). 
 
 Parinaud, Brain, ix. 330, 1887 (cited by Straub), 5 cases. 
 
 Stolting and Bruns, Arch, fiir Ophth. xxxiv. 3, 1888 (cited by 
 Straub). 
 
 Benzler, Deutsch. militar-aerztl. Zeitschr., xviii. (cited by Straub). 
 
 Peters, Centralbl. f. pract. Augenheilk., xiii. (cited by Straub). 
 
72 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 Sanviiif.MU. Ti'.-iiis. VI II. Iii1cni;it. Oi)litli. ( 'oufirt'ss. KdiiiburKh, 
 1S!»4. 
 
 Straiib, M., Arch, of Ophtli., xxv. :i (18%). 
 
 Hayne, H. W., ib. 
 
 Graefe's 10 cases (cited by Straub) come rather uikU'V the head of 
 convergence-insufficiency than actual paralysis. 
 
 Much more frequent and important are those cases in 
 which there is simply a greater or less weakness of conver- 
 gence (Convergence = insufficiency). A. Graefe, who re- 
 garded these cases as quite rare, gives an excellent expo- 
 sition of some ef the physical signs of the condition in a 
 paper read before the Seventh Ophthalmological Congress 
 (1888). Tn their entirety these s/'(/its may be stated as fol- 
 lows: 
 
 For distance. Lateral orthophoria or slight exophoria 
 (l?-2'°) by all tests (screen, parallax and phorometer) . As- 
 sociated lateral movements practically normal. Associated 
 vertical and oblique movements of ten restricted (frequently 
 in an asymmetrical manner) and field of binocular single 
 vision often* markedly limited in some one direction above 
 or below, indicating a weakness of an elevator or depressor 
 (particularly the superior rectus). Diverging power (ab- 
 duction) not over 9", frequently subnormal (5^-6). Prism- 
 convergence (so-called adduction) often, although not 
 always, restricted, being acquired with difficulty and per- 
 formed with effort.! 
 
 For near. Marked exophoria by all tests (/. r. exophoria 
 of 7^ or over by both phorometer and parallax, and notice- 
 able deviation out behind the screen). Associated "lateral 
 movements normal. Pc (near point of convergence) 3" or 
 over from the root of the nose, and maintenance of eyes in 
 position of extreme convergence for more than a moment 
 difficult or impossible. Convergence near-point about the 
 same whether the object is approximated from a point to 
 the right or from a point to the left of the median line. If, 
 
 *In about 20 per cent, of the case.s that I have ob.servcd. In these ca.ses there is 
 often hyperphoria for distance in the primary position. 
 
 tThat is. the primary adduction (t. e the greatest amount that the patient can be 
 not to do at the first trial) will be only 8° or 1-'", and the addition of even 1° or 2° to 
 this will produce insuperable diplopia. Moreover, the e.xertion of overcouiintf a 
 prism of even this imiouut is associated with a sense of strain, and tlie patient, if he 
 does succectl in oviriomiiij.; the prism for a moment, cannot lu>M the images together. 
 These features constituti- a marked difference from those obtaining in normal eyes 
 which, though they may have difficulty in learning to overcome prism-- l>:is( out will 
 do so with ease and with rapidly increasing facility after a few trials 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 73 
 
 when the convergence near-point is reached, one eye be 
 screened and then th6 object of fixation is carried still 
 closer to the nose, the uncovered eye will, although with 
 difficulty, turn in still further, in order to follow the object, 
 while the eye behind the screen will diverge by an equal 
 amount (preservation of associated adduction, failure of 
 convergence -adduction. — Graefe). 
 
 Graefe's test indicates that the eouvei-gence is relatively weak — 
 weak, that is, as compared with the absolute power of the eye to 
 move inward (associated adduction) . But whether this indicates an 
 absolute weakness of convergence or not depends upon whether we 
 regard the associated adduction (ability of the eye to move inward 
 while its neighbor moves outward) as always normally less than the 
 convergence adduction (ability of the eye to move inward while its 
 neighbor is also moving inward). Graefe proceeds upon the assump- 
 tion that this is the case; but in many persons, whom I examined 
 and who had apparently normal eyes, the associated adduction 
 seemed the greater of the two. In such the fact that they responded 
 to Graefe's test would not necessarily indicate the existence of any- 
 thing abnormal, 
 
 As to its nature, convergence-insufficiency may be either 
 accommodative or non-accommodative. Non accommoda= 
 tive insufficiency may be due (A) to direct weakness of the 
 interni, e. rj. that obtaining after a complete tenotomy of 
 the latter, especially when the operation has been done 
 upon faulty principles, as to relieve a divergence -insuffi- 
 ciency not associated with excess of convergence. This 
 post-operative weakness, which may give rise to a very 
 troublesome asthenopia lasting for several months, is, to 
 be sure, not really an example of convergence-insufficiency, 
 being really a traumatic paresis of the interni, but in its 
 symptoms and course it so much resembles the former as 
 to be most conveniently considered in connection with it. 
 
 Convergence -insufficiency again occurs (B) .secoiidrfrili/ 
 to a direryeuce-excesK — this being an example of that com- 
 pensatory action, already alluded to, by virtue of which a 
 deviation, which is at first marked for one distance only, 
 tends to become generalized so as to become apparent for 
 all distances alike. In these cases there is at first a marked 
 exophoria for distance accompanied by excessive diverging 
 power (10 or over), but with only moderate exophoria for 
 near, good converging power, and no recession of the near 
 
74 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 point of convergence. Later, the exophcria for near in- 
 creases markedly (without there being necessarily any in- 
 crease in the exophoria for distance), the convergence 
 near-point recedes, and the converging power gets to be 
 performed with more and more difficulty. From some few 
 observations that I have made I think it likely that this 
 sort of extension of exophoria may occur chiefly in young 
 persons as a result of the processes of growth, which, as is 
 well known, favor the development of a divergence of the 
 visual lines and which may abrogate a convergent strabis- 
 mus or convert a case of parallelism of the visual axes into 
 one of divergent squint. 
 
 If this explanation is correct these cases are instances of 
 a gradually developing bilateral insufficiency of the interni, 
 rather than a real insufficiency of convergence. 
 
 A similar explanation — viz., the gradual production of 
 an anatomical divergence by developmental processes 
 taking place during the period of growth — may perhaps 
 account for the genesis of some of the cases of convergence- 
 insufficiency not complicated with a divergence-excess. 
 
 Another variety (C) of non-accommodative convergence- 
 insufficiency appears to be directly dependent upon an 
 iitsitfiriencii of an elevator or depreeKor muscle, and partic- 
 ularly of the superior rectus. This connection, in view of 
 the assistance that these vertically acting muscles give in 
 effecting adduction, seems not unnatural and, at all events, 
 appears to be quite frequent. Thus in 21 successive cases 
 occurring in my practice 6 exhibited marked insufficiency, 
 or actual paresis of the vertical muscles, and in another 
 series of 27 that I examined 5 at least were thus affected. 
 
 In three or four other cases there was more or less weak- 
 ness of the superior and inferior recti of both eyes, caus- 
 ing a concentric limitation of the field of single vision. 
 This weakness, from its varying character, could not be 
 regarded as due to paresis, but was (D) simply one of the 
 evidences of the general lack of inuscular poicer and niKsca- 
 lar co-ordination that these patients presented. Such cases, 
 therefore, appear to occur especially in neurasthenia. 
 In the latter condition, at any rate, and in allied conditions 
 of general enfeeblement, convergence-insufficiency is of 
 
NEW CLASSIFICATION OP MOTOR ANOMALIES. 75 
 
 frequent occurrence and often occasions a troublesome 
 and intractable asthenopia which disappears only when 
 the causal affection has been removed. 
 
 Accommodative convergence=insufficiency consists in 
 the development of a marked divergence for near points 
 due to non-use of the accommodation. Accommo- 
 dation being usually associated with convergence, any 
 condition which prevents the discharge of accommodative 
 impulses will likewise tend to inhibit the convergence. 
 Theoretically this inhibition should occur in all cases, but 
 practically it occurs in a minority only. These cases may 
 be classified as follows : 
 
 (a) Patients with tiHcorrecfed mi/opia , in whom there is 
 but little necessity for using the accommodation at all. 
 
 (b) In Jniperinetropef:-, who having all along accustomed 
 themselves to using their accommodation without employ- 
 ing a corresponding convergence acquire thereby a rel- 
 ative insufficiency of the latter function, which comes to 
 light as soon as their hypermetropia is corrected. 
 
 Thus a mail with a hypermetropia of 2 D. has been accustomed 
 when looking at an object 13" off to use an accommodation of 5 D.; 
 but when his hypermetropia is corrected by glasses, he suddenlj- 
 finds that at this distance he has to iise only 3 D. of accommodation, 
 an amount with which he has been wont to associate a much smaller 
 degree of convergence. Not being able at first to accustom himself 
 to these new conditions, /. c. not l^eing able at once to converge to 
 a point at 13" witliout using 5 D., his visual lines diverge. This di- 
 vergence often gives rise to considerable trouble (persistence of 
 asthenopia, etc.) and constitutes one of the chief reasons why con- 
 vex glasses are not tolerated by many hypernietropes. 
 
 For a similar reason convergence -insufficiency may de- 
 velop (C) in in-e.sht/opes who first put on convex glasses for 
 near. 
 
 The marked increase in a convergence-insufficiency gen- 
 erally produced by (D) the continuous use of 2^nK»is, 
 base in, is also probably in part due to accommodative 
 inaction; the use of such glasses by favoring divergence 
 tending to relax the accommodation still more and hence 
 to superinduce a still further failure of the convergence. 
 
 The rouvKeoi a convergence-insufficiency varies greatly. 
 Many cases, particularly those dependent upon general 
 muscular and nervous weakness remain about the same 
 
76 
 
 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 for a long time and then improve as the causal condition 
 improves. Such cases may also show recurrences, when 
 for any reason there is a new deterioration of the vital 
 forces. Cases also of accommodative convergence-insuffi- 
 ciency due to a readjustment of the optical conditions under 
 which the patient has been working (application of convex 
 glasses for hypermetropia and presbyopia) usually get well, 
 the patient accustoming himself after a while to his new 
 refractive state. This is, however, by no means always 
 the case, and, if a tendency to convergence -insufficiency al- 
 ready exists, it may become aggravated and be made per- 
 manent by the use of glasses— indeed, the development of 
 an actual strabismus divergens m^y be thus superinduced, 
 particularly when the glass chosen for a hypermetropic 
 child has been somewhat in excess of the true hyper- 
 metropia. 
 
 Convergence -insufficiency due to tenotomy also gener- 
 ally tends to disappear, although this again cannot be 
 taken as the invariable rule. 
 
 Other cases of convergence-insufficiency, and partic- 
 ularly those occurring in young persons and dependent 
 upon an insufficiency of the elevators and depressors, tend 
 to increase. This seems to take place by the development 
 of a divergence -excess in accordance with the law of 
 compensation already several times referred to, by which 
 a non-comitant deviation tends to become comitant. The 
 course of such cases, if unchecked, is first increase of 
 the exophoria for near, second development of exophoria 
 for distance also, with increased diverging power (Di- 
 vergence excess), next the appearance of an actual diver- 
 gent strabismus for near with considerable exophoria for 
 distance (Periodic squint), and finally divergent strabis- 
 mus for both distance and near (Constant squint) . This ten- 
 dency to a constantly increasing divergence may be favored 
 by the injudicious use of convex glasses and particularly by 
 the use of prisms base in, which almost always tend to 
 make the exophoria greater and greater.* 
 
 *I observed one marked case of this sort, occiirrinsr in a Kirl of nine, who at first 
 had 3"^ of exophoria for distance and over 6° for near, but wlio after iisinjr prisms for 
 a year had for distance exophoria of .S" with abduction of lO'^-lJ" and spontaneous 
 crossed dii)lopia. aiul for near exophoria of 15°. rrism-couverEeiice (adduction) 0^. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 77 
 
 As has been seen, convergence-insufficiency may be 
 compHrafed with an insufficiency of one of the vertical 
 muscles, the latter affection, indeed, in these cases prob- 
 ably being the cause of the former. In other cases, a di- 
 vergence-excess is present which ie sometimes the 
 cause, but more often the effect, of the convergence-insuf- 
 ficiency. The latter may also, particularly in those whose 
 muscular system generally is weak, be complicated with a 
 divergence-insufficiency.* Slight cases of this sort, in 
 which the insufficiency of divergence is not great 
 enough to produce esophoria for distance constitute the 
 asthenic exophoria of Savage. 
 
 The si/mjjfom.sot convergence-insufficiency are astheno- 
 pia, either simple, or associated with headache and pain in 
 the eyes, conjunctival irritation, and spontaneous diplopia, 
 producing blurring of vision for near work. Asthenopia is 
 a pretty constant symptom, being met with in all the va- 
 rieties, although in my experience more apt to occur in the 
 non -accommodative than in the accommodative form. It 
 is often very marked and may incapacitate the patient from 
 doing near work. 
 
 The symptoms are by no means necessarily in direct re- 
 lation with the amount of the deviation, being, in fact, 
 more pronounced in deviation of medium degree than in 
 those which have assumed the proportions of a regular 
 squint. 
 
 It is for this reason, probably, that the use of concave glasses in 
 myopes affected with convergence-insufficiency sometimes causes 
 distress; since these glasses tend to increase the impulse to converg- 
 ence and thus rediiee a large deviation, which is insuperable and 
 gives no trouble, to a smaller one which can be overcome by effort 
 and hence gives more annoyance. On the other hand, Avhen the de- 
 viation is very small to begin with, the symptoms may be aggravated 
 by the use of convex glasses and of prisms base in, which tend to 
 make it larger and therefore more troublesome. 
 
 The treatment of convergence-insufficiency must aim 
 first at removing the cause of the trouble. Hence in neu- 
 
 By exercise of the convergence with prisms the exophoria for distance was reduced 
 to 0°-3°, that for near to 5°-6°, the prisni-converRence was raised to 40°-50°, and there 
 was no more spontaneous diplopia. This improvement was maintained up to the 
 time that the patient was last seen (7 months after the treatment had been discon- 
 tinued). 
 
 *I liave notes of a case of this sort in a myope of 8-10 D., in whom there was an 
 esophoria of 14-20° (i. e. a real convergent squint) for distance, with diverging power 
 of 2-3°, and exophoria of 8° for near. 
 
78 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 rasthenia general strengthening measures (out-of-door 
 exercise, tonics) are indicated and are for the most part 
 successful. Accommodative convergence - insufficiency 
 requires the careful correction of the refraction in myopia, 
 while in hypermetropia frequently an under-correction will 
 be indicated. Indeed, it is a safe general rule to fully cor- 
 rect myopia and to under-correct hypermetropia whenever 
 much exophoria exists; and in presbyopia under the same 
 conditions to give a weaker convex glass than would other- 
 wise seem indicated. 
 
 The immediate causal indication requires trahuiKj oftha 
 convergence, which can, in general, be effected by system- 
 atic exercise with prisms base out. This often gives strik- 
 ingly good results, but in some cases fails altogether. 
 
 The wearing of prisnix base in should be resorted to only 
 as a temporary expedient, on account of their tendency to 
 produce increase of the trouble; and these prisms should 
 be discontinued at once as soon as signs of such an in- 
 crease begin to manifest themselves. 
 
 Finally, if an ojwration is decided upon, advancement of 
 the interni, coupled, in case a divergence-excess is pres- 
 ent, with a tenotomy of the externi, should be made. Te- 
 notomy of the externi alone seldom gives any lasting re- 
 sult. 
 
 Hyperklneses. 5pasm and Excess of Convergence. 
 Marked tonic spasm of convergence, so that both eyes are 
 turned strongly inward, has been observed in hysteria. 
 
 Minor degrees of over-action of convergence (Converg- 
 ence=excess) are of frequent occurrence. They may be 
 either accommodative or non-accommodative in character. 
 
 lYie ijhysical siffnx oi a convergence- excess not compli- 
 cated with a divergence-insufficiency are as follows: 
 
 For distance. Orthophoria or moderate esophoria ( 1 -3 ) 
 by all tests (phorometer, screen and parallax). Associ- 
 ated lateral movements normal. Diverging power normal 
 or but slightly subnormal (S^'-S^). Prism-convergence 
 (adduction) normal in amount, rapidly acquired, and easy 
 to produce and maintain. Exercise of convergence not 
 infrequently causing the development of temporary homo- 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 79 
 
 nymous diplopia. Homonymous diplopia sometimes also 
 producible by will and apparently without effort. 
 
 For near. Esophoria by all tests, often exceeding that 
 for distance.* Convergence near-point li"-l" or less. 
 
 Non=accommodative convergence=excess may be either 
 (a) idiopathic or may (b) be secondary to a condition of 
 divergence-insufficiency. The former appears to be rare, 
 although I have met with two or three cases. The second- 
 ary variety, on the other hand, appears to be quite com- 
 mon, and develops according to the compensatory law by 
 which deviations in general, tend to become equalized for 
 distance and near. In this case, of course, there will be 
 marked esophoria for distance and the diverging power 
 (abduction) will be much reduced. 
 
 Non-accommodative convergence-excess probably com- 
 prises most of the cases described by Savage under the 
 name of sthenic esophoria. 
 
 Accommodative convergence = excess (Accommodative 
 esophoria, Accommodative convergent squint, Pseudo- eso- 
 phoria) is very frequent. It occurs under the following 
 conditions : 
 
 (a) Uncorrected Jiyperhtefropia. The effect of this in 
 producing inward deviation of all degrees from a slight eso- 
 phoria to a marked strabismus is too well known to require 
 further comment here. 
 
 (b) In iiii/ojjes who for the first time use a concave glass 
 for near points. Such patients will add to the natural 
 amount of convergence for the point they are looking at 
 (which convergence they have hitherto been accustomed to 
 make without using any accommodation) the extra conver- 
 gence imposed in sympathy with the accommodative effort 
 that they now make for the first time. 
 
 (c) In presbt/opes (particularly, hyperopic presbyopes) 
 at the beginning of the presbyopic period. These patients 
 have to exert a very strong effort in order to stimulate their 
 flagging accommodation to the point necessary for distinct 
 
 *Unless, however, the patient really fixes upon the test object, the esophoria for 
 near may vary greatly and even be replaced temporarily by exophoria. This is par- 
 ticularly apt to be the case in accommodative convergrence-excess, where the amount 
 of hypermetropia may ce such as to prevent the patient from seeing the object dis- 
 tinctly. 
 
80 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 vision, and in sympathy with this excessive call made upon 
 the accommodation an excessive effort of convergence is 
 simultaneously made. 
 
 (d) Af< the rei^nlt of thf instillntioti of a ynydriatic. The 
 increase of a convergent squint by the instillation of atro- 
 pine was observed by Long and Barrett (Ophth. Hosp. Re- 
 ports, xii. 1888-1889), who found that it occurred in 11 
 cases out of 38 in whom this mydriatic was employed. 
 These cases, however, had been under the influence of the 
 atropine for several days. In cases which are but recently 
 under the influence of the mydriatic an increased tendency 
 to convergence due to the latter appears to be even more 
 frequent. Under these circumstances esophoria may de- 
 velop where orthophoria existed before, and a pre-existing 
 esophoria of moderate amount may develop into a well- 
 marked convergent squint. 
 
 The t'orrect explanation of this phenomenon was first g'iven by 
 Savaj^e, althougli I myself came independently to the same conclu- 
 sion. The converg'ence here is evidently due to the excessive effort 
 which the patient makes to see distinctly under the unusual condi- 
 tions presented by mydriasis. Not bein^ aware that he cannot accom- 
 modate, he makes a violent effort to do so, and in making this effort 
 sends out a correspondingly strong impulse for convergence. The cili- 
 ary muscle does not respond, but the interni do; and, as the impulse 
 was excessive, they I'espond by producing an excessive convergence. 
 The condition, in fact, is quite analogous to the excessive secondary 
 deviation of the sound eye when its fellow attempts to perform fixa- 
 tion by means of a paralyzed nniscle. 
 
 As under the mydriatic the sight is more blurred for near 
 than for distance, this fruitless effort to see distinctly by 
 attempting to put into motion a paralyzed accommodation 
 will be more excessive, and hence too the esophoria will be 
 more pronounced, for near points. For distance, the eso- 
 phoria will generally be greater in proportion to the degree 
 of hypermetropia and the consequent blurring of sight, and 
 will often disappear altogether as soon as the refraction is 
 corrected. These facts are shown in the following cases: 
 
 EsopHoKiA. Lakhk ixcrkask undkr mydriatic. Miss K., aged 
 20. Refraction (under homatropine) -f- 0.2.') sph. O -f O.'iO cyl. ax. 
 V, each. When not under mydriatic shows esophoria '-^1° for both 
 distance and near (with and without correction of refraction): di- 
 verging power, (»' I'lider liomatropine, witli<»ut correction of refrac- 
 tion. (■s()i)lioriM for distance over S". for near over 1.")"^. diverging 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 81 
 
 power 8°. I'lidcr lioniatropinc, witli conrctioii of rt'fraotion, t-so- 
 phoria for distance ;")', for near over 1')". 
 
 2. J. B., male, aged 15. Hypernietropia (lioniatropine) O.-OU 1). 
 Before homatropine, esophoria 3° for distance, ()' for near. Under 
 lioniatropine, (witli and without correction of refraction), 2'/-.'° for 
 distance, 7° for near. Diverging power 4°. 
 
 3. Kath. S., aged 32. Hypernietropia 2.2;il) (under homatropine). 
 Before homatropine, esophoria 2°-^° for distance, 1° for near; di- 
 verging power 5°. Under homatropine, without correction of refrac- 
 tion, 12''-20° for distance, 12° for near (i. e. has an actual convergent 
 squint). Under homatropine and with correction of refraction, eso- 
 phoria '/j° for distance; little, if any for near. 
 
 The course in case of convergence-excess is very vari- 
 able. The accommodative variety, in particular, often 
 decreases or disappears spontaneously either as a result 
 of developmental changes, favoring the genesis of a diver- 
 gence, or in consequence of the decrease of the hyperme- 
 tropia, or because the patient gives up the accommodative 
 effort and with it the effort to converge. Its usually speedy 
 and total disappearance in cases coming under cate- 
 gories B, C, and D above given, is to be ascribed to the 
 last mentioned cause. 
 
 In other cases, particularly in the very young who are 
 beginning to tax their accommodation more and more with 
 school work, the deviation increases ; the regular course 
 being, first, increase of the esophoria for near, then 
 increase of the esophoria for distance with reduction of the 
 diverging power (Development of divergence-insuffici- 
 ency), next the development of an absolute squint for 
 near points where accommodative effort is most required 
 (Periodic squint) , and lastly strabismus convergens marked 
 for both distant and near (Constant squint). A squint 
 when thus fully developed usually remains permanently, 
 but may disappear in latter life through the agencies 
 mentioned in the preceding paragraph. 
 
 As already noted, convergence -excess may be coinjili- 
 cated with divergence-insufficiency, the latter condition 
 being either the cause or the effect of the former. It is 
 also frequently complicated with some form of vertical de- 
 viation, producing hyperphoria in addition to the esopho- 
 ria. It seems, in fact, not unlikely that these vertical de- 
 
82 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 viations play an important part in the genesis of the 
 excessive tendency to convergence. 
 
 The si/iNp/oh/s of convergence -excess are asthenopia, 
 headache, and spontaneous homonymous diplopia, with 
 sometimes more marked reflex disturbances. These symp- 
 toms, however, are much less pronounced and constant 
 than in cases either of convergence-insufficiency or diver- 
 gence-insufficiency, and when present are usually due to 
 the attendant hypermetropia or, at least, disappear when 
 the latter is corrected. 
 
 The treafiiienf of convergence-excess is largely causal, 
 consisting particularly in the correction of the refraction. 
 In doing this we shall do well to follow the rule that when 
 there is marked esophoria and, particularly, when there is 
 more esophoria for near than for distance, we must fully 
 correct any hypermetropia and, on the other hand, under- 
 correct any myopia, that may be present. 
 
 The result of treatment, both as regards the removal of 
 the deviation and the relief of the symptoms are very 
 good. Even in well-marked convergent squint a cure is 
 effected much oftener than is generally supposed, the 
 only requisites being that the refractive treatment should 
 be kept up long enough (a year at least)"* Long and 
 Barrett (1. c.) analyzing the results in 102 cases, found 
 that a complete cure was effected in 37, while out of 61 
 cases under 10 years of age 27 (or 44 per cent.) were cured. 
 
 In addition to correcting the refraction we may try to 
 break up the excessive tendency to convergence by aool- 
 ishing the accommodation altogether for a time. This we 
 effect by keeping the eyes under afropine for a number of 
 days or even several weeks. This may also, if Long and 
 Barrett's figures hold good generally, be used as a means 
 of prognosis, for these authors found that of 5 cases which 
 were improved by atropine all were subsequently improved 
 by glasses, while of 6, in whom the deviation was not 
 affected by the atropine, only 3, and of 4, in whom the 
 atropine made the convergence worse, only 1 received any 
 relief from the correction of their refraction. 
 
 *This, becomes the coiiliinioiis relaxation of the interiii thus pioiliKid allows the 
 weakened extenii to act to Ri eater ad v:inta);e aiul finally to regain tlieir tone (UonK 
 and Harretl). 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 83 
 
 Exercise of the divergence with jtris/ns is of no service 
 in this condition, and the wearing of prisms base out is to 
 be deprecated as tending to perpetuate and increase the 
 deviation instead of curing it. 
 
 If these means fail and an opera f ion is thought advioable 
 on account of the deformity or the symptoms, tenotomy of 
 the interni may be done, combined, in case a divergence- 
 insufficiency is present, with an advancement of the ex- 
 terni. 
 
 VIII. 
 ANOMALIES OF DIVERGENCE. 
 
 Hypokinesis. Divergence=Insufficiency. Weakness of 
 the diverging power (Divergence-Insufficiency)is charac- 
 terized by the following signs : 
 
 F'or Distance. — Esophoria of varying amount (usually 
 2''-8'^), by all tests (phorometer, screen, and parallax). 
 Associated lateral movements normal. Diverging power 
 very much reduced, the reduction being often proportion- 
 ate to the degree of the esophoria ( e. g., with an esophoria 
 of 3" or 4°, the diverging power is about 4", and with an 
 esophoria of 5° or 6°, the diverging power is only 2°) . In 
 the typical cases of this anomaly, however, the diverging 
 power is disproportionately low, being, for example, only 
 2° or 3°, when the esophoria is 1° or 2"', and being, perhaps, 
 only 3° or 4° when there is orthophoria or actual exophoria 
 for distance. Exercise of divergence with prisms, base in, 
 is sometimes associated with a sense of decided muscular 
 strain. 
 
 Prism-convergence (adduction) normal, or often some- 
 what deficient. Exercise of the convergence often gives 
 rise to a temporary homonymous diplopia, and the latter 
 may also in some cases (particularly when the diverging 
 power is much reduced) occur spontaneously, or be 
 evoked by simply placing a red glass before one eye. 
 
 For year. — Signs, unless the condition is associated 
 with a convergence-insufficiency, or with a convergence- 
 excess, fairly normal ( /. e., slight esophoria or exophoria, 
 
84 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 and convergence near-point at about the proper distance). 
 
 In its orii/in divergence- insufficiency is either idiopathic 
 or secondary to a convergence-excess. 
 
 Uncomplicated i<li<>i><ttliic divergence-insufficiency is 
 comparatively rare, and, moreover, some of the cases that 
 would seem to fall in this category are probably either 
 really secondary to some disorder of the vertical muscles 
 (elevators or depressors), or are examples of a spurious 
 divergence-insufficiency, /. r., of a condition in which 
 there is actual weakness of the externi themselves, either 
 natural or produced by operation. In cases of the latter 
 kind the divergence is indeed weak, but the power of mak- 
 ing lateral movements is also lessened, and hence these 
 cases do not fairly come under the head of a simple im- 
 pairment of the diverging function. 
 
 Complicated idiopathic divergence-insufficiency is more 
 common. In these cases there is either a convergence- 
 insufficiency, which has developed simultaneously with the 
 disorder of divergence, or there is a convergence- excess, 
 which is the result of the latter. 
 
 SeroiKhtri/ <lii'('i'{ieiK'e-hisnfficietic;i develops in the man- 
 ner already described (see Section VII.) from a progress- 
 ively increasing convergence-excess. Cases of this sort 
 might be confounded with those of the foregoing category, 
 /. f., those in which a primary divergence-insufficiency is 
 followed by excessive convergence action. The distinc- 
 tive points between the two may be stated as follows: 
 
 PRIMARY I)IVKR(iEXCK - INSUFFI 
 CIKNCY. WITH SECONDARY CON- 
 VKRCiKNCK-EXCESS. 
 
 Ks()i)li()ria for distancf nioder- 
 
 PRIMARY CON YER(4EX< E-EXCESS . 
 WITH SECONDARY DIYEJiGENCE- 
 INSUFFKTENCY. 
 Esoplioj-ia for (listaiicc often 
 
 ate (not ovc'i- S'').aii(lniaybe less jrreat, and when small usnallx 
 than tlitMh'liciency ititlie divei-.u-- I disi)roi)ort ionately larue in coin- 
 
 injj- jxnver (aliilnction ). 
 
 Ksoi)horia f<.r iieai- small and 
 usually less than that for dis- 
 tance. 
 
 ( 'ondition stationai-v. 
 
 parison with the delieiem-y of di- 
 veryiii^- power. 
 
 Ksophoria for near usnally 
 greater tliaii for distance. 
 
 ( 'ondition ofl<'n ])ro^n-essive. 
 
 The ro///-.s7 pursued by a divergence-insufficiency is in- 
 dicated in what has already been said. The idiopathic 
 variety shows l>ut iitth" tondoncy to change, the amount of 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 85 
 
 esophoria and of divergence-weakness often remaining the 
 same for years. This variety frequently becomes compli- 
 cated with a condition of convergence-excess, which, how- 
 3ver, also remains of moderate degree. On the other hand, 
 a divergence-insufficiency, which is secondary to a con- 
 vergence-excess, is often progressive, the advance contin- 
 uing in many cases until a moderate deviation is converted 
 into a marked and constant strabismus convergens. 
 
 The si/)i/j)/oins of a divergence-insufficiency are often 
 very troublesome. Asthenopia as a result of near work is 
 not so much complained of, unless there is a simultaneous 
 convergence-insufficiency, but headache and other more 
 remote reflex pains, a sense of constriction in the head, 
 stomach disturbance, general inertness and lassitude, and 
 even interference with the general nutrition are often met 
 with. Spontaneous diplopia may also occur, being, nat- 
 urally, more marked for distance than for near. One 
 peculiarity in the symptoms is that headache and pro- 
 nounced asthenopic sensations (feeling of strain and 
 tiring in the eyes) , together with a sense of confusion and 
 dullness in the head, are especially apt to be produced by 
 looking long and intently at distant objects, particularly 
 when moving or when brightly illuminated. Such symp- 
 toms are hence often occasioned by watching a theatrical 
 performance, a ball-match, a procession, or a moving 
 throng of people. (Panorama-asthenopia, or panorama- 
 headache of Bennett.)* 
 
 The freafment of divergence-insufficiency presents many 
 difficulties, the condition being intractable and the result 
 uncertain. 
 
 Direct exercise of the divergence with prisms, base in, 
 has not, in my experience, been of the least avail. Exer- 
 cise by the performance of systematic lateral movements 
 of the eyes seems unphysiological, inasmuch as it is the 
 externi that are thus practiced, and not the function of di- 
 vergence per !<(^, and, moreover, in these movements the 
 interni are practiced along with the externi. Some, how- 
 ever, seem to have obtained good results by this method. 
 
 The constant wearing of prisms, base out, is in most 
 
 *Annals of Ophthalmology, January, 1897. 
 
86 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 cases a dangerous expedient, as tending to cause disuse 
 and a consequent further enfeeblement of the abducting 
 power. 
 
 If an operation is resorted to, it should, in the idiopathic 
 cases at all events, be an advancement of the externi 
 rather than a tenotomy of the interni. The latter opera- 
 tion by itself is almost always nugatory, the condition 
 tending, after a temporary period of improvement, to re- 
 turn to its original state. Moreover, the tenotomy, if 
 thorough enough to be efficacious, is liable to substitute for 
 the unpleasant asthenopia for distance an almost equally 
 annoying asthenopia for near. In the secondary cases, 
 however, or wherever a marked convergence-excess is 
 present, tenotomy of the interni may be performed; but 
 even then it is preferably combined with advancement of 
 the externi. 
 
 Hyperkinesis. Divergence=Excess. Over-action of di- 
 vergence (iJirt'nitiKu^-E.i'crss) is marked by the following 
 signs : 
 
 For dhtance. Exophoria, usually marked (from 4 up- 
 ward) with noticeable deviation out behind the screen. 
 Associated lateral movements normal. Diverging power 
 excessive (over 9"), the excess over the normal amount of 
 6" or 8^ being often roughly proportioned to the degree of 
 the exophoria, but sometimes being disproportionately 
 larger. Prism-convergence (adduction) in uncomplicated 
 cases normal, although possibly performed with difficulty 
 at first. Crossed diplopia for distance often occurring 
 spontaneously, or producible at will. 
 
 For vcar. Conditions, unless a convergence-insuf- 
 ficiency also exists, fairly normal (/. (\, exophoria less, or, 
 at all events, not much greater, than for distance, and near 
 point of convergence about in its normal situation). 
 
 A divergence-excess may either be primary in or/'oiu or 
 be secondary to a convergence-insufficiency. 
 
 /'riiiiffrt/ divergence-excess occurs not infrequently as 
 an uncomplicated affection, but still more often is asso- 
 ciated with a vertical deviation (which may really stand 
 in genetic relation with it), .)i' with n consecutive convcrg- 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 87 
 
 ence-insufficiency, It may also be associated with a 
 convergence-excess. I have observed several instances of 
 this latter combination, in which, with exophoria for distance 
 and a high diverging power, there was also excessive power 
 of convergence, and either actual esophoria for near, or at 
 least an exophoria slight in amount, and much less than 
 that for distance. 
 
 The development of a st^roiidarn divergence-excess from 
 a convergence-insufficiency has already been traced (see 
 Section VIII). These cases, like the simple ones of con- 
 vergence-insufficiency which represent only a less ad- 
 vanced stage of the same process, often show complicating 
 insufficiency of the vertical muscles. Indeed, as before re- 
 marked, this last-named condition would seem to consti- 
 tute the real cause of the divergence which takes place, 
 first for near and then for distance. 
 
 The differential points between a primary divergence - 
 excess with a secondary convergence -insufficiency and a 
 primary, convergence-insufficiency with consecutive di- 
 vergence-excess are as follows: 
 
 PRIMARY mVERGENCE - EXCESS I PRIMARY CONVERGENCE-INSUFFI- 
 WITHSE:!0NDARY CONVERGENCE- | CIENCY WITH SECONDARY Dl- 
 INSUFPICIENCY. | VERGENCE-EXCESS. 
 
 Exophoria about equal for dis- Exophoria for near much great- 
 
 tance aud near. er than for distance. 
 
 Converging power and prism- Convergnig power greatly at- 
 
 convergence not excessively af- fected. 
 fected. 
 
 Recession of convergence near- Recession ot convergence near- 
 point moderate. point marked. 
 
 Condition shows little tendency Often markedly progressive, 
 to progress. 
 
 As above stated, cases of primary divergence-excess 
 show but little tendency to progress. I have had one 
 such case under observation for over nine years, in which 
 the divergence, although large, has shown but moderate 
 fluctuations — indeed, may be said to have remained prac- 
 tically unchanged— during the whole time. Cases, on the 
 other hand, of secondary divergence-excess are often prog- 
 gressive, a moderate degree of exophoria developing 
 gradually into a marked divergent squint. 
 
 The si/ijipfoii/s presented by a case of divergence -excess 
 are frequently slight. The most troublesome are those due 
 
88 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 to an associated convergence-insufficiency, and, if this is 
 absent, the patient may complain of nothing except possi- 
 bly of a spontaneously occurring crossed diplopia for dis- 
 tance, or of the deformity occasioned by the noticeable de- 
 viation of the eyes. Headache and asthenopia may, how- 
 ever, also occur. 
 
 The firaftneiif of a divergence-excess will be addressed 
 mainly to the correction of the refraction and to the relief 
 of an associated convergence-insufficiency. If an opera- 
 tion is performed, tenotomy of the externi may be done; 
 but it will often have to be supplemented by systematic 
 exercise of the convergence and even by advancement of 
 the interni. 
 
 IX. 
 
 ANOMALIES OF SURSUMVERGENCE. 
 
 Hypokinesis. Sursumvergence=lnsufficiency. It is not 
 
 certain whether sursumvergence, /. c, the separation of 
 the visual lines in a vertical plane, is ever performed by 
 the eyes in the execution of normal movements. It seems, 
 however, likely that some such action may be serviceable 
 incidentally in the act of elevating or depressing the eyes. 
 If so, great impairment of the sursumvergence would con- 
 stitute a serious deficiency. As far as I have seen, how- 
 ever, limitation of sursumvergence appears to have no 
 special injurious effect. 
 
 Those who regard the amount of sursumvergence as a 
 measure of the strength of the elevators and depressors 
 (which it surely is not) lay more stress than I have done 
 on the limitation of this function, and recommend system- 
 atic exercise of the latter by means of prisms, base up or 
 down, in cases where it is subnormal. I have had some 
 experience with these methods, but not enough to enable 
 me to speak with assurance as to their value. My results, 
 such as they were, have not led me to expect much from 
 training of this sort. 
 
 Hyperkinesis. Sursumvergence-Excess. Excessive power 
 of sursumvergence is observed in many patients affected 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 89 
 
 with hyperphoria and particularly in myopes who have an 
 artificial hyperphoria from wearing ill-fitting concave 
 glasses. The latter, as they shift in various positions, 
 produce prismatic effects changing in degree and in direc- 
 tion, and hence requiring a variable effort to overcome the 
 diplopia to which they would naturally give rise. This 
 constant exercise gives rise often to a considerable in- 
 crease in the power of sursumvergence, the latter some- 
 times attaining 10° or more. 
 
 A true su rsK Nifergenre-excess, i. e., a state of habitual 
 divergence of the visual lines in a vertical plane, due to 
 excess of sursumvergence action, constitutes one of the 
 varieties of hyperphoria, and probably accounts for some 
 of the cases of strabismus sursumvergens and strabismus 
 deorsumvergens. These cases must not be confounded 
 with a similar vertical deviation due to paresis or insuf- 
 ficiency of some of the individual muscles. The differen- 
 tial diagnosis between the two will be established by mak- 
 ing the screen and diplopia tests in different portions of 
 the field of fixation, when, if there is an insufficiency of 
 any individual muscle, a deviation or a diplopia, showing a 
 characteristic increase in some one direction of the gaze, 
 will be found to exist (see Section VI). 
 
 In sursumvergence-excess either the right or the left 
 visual line may be habitually higher than the other ( r'Kjltt 
 and left Jiyperphoria ), or each alternately may be higher 
 (alternating liuperphoria). If the deviation is considera- 
 ble and not habitually overcome, the condition is known 
 as a vertical squint (ht/pertropia ), which again is called 
 right or left hypertropia, according as the right or the left 
 visual line is above. Vertical squint is also classified into 
 strabisinus sursumvergens when the lower eye is the one 
 that habitually fixes, and strahisiitus deorstiinvergens when 
 the upper is the fixing and the lower the non-fixing eye. 
 
 Regularly, in such cases, the deflection follows the law 
 of associated movements. That is, if the right eye devi- 
 ates up behind the screen when the left eye is fixing, the 
 latter will, when the screen is shifted so as to cover it, 
 move down in company with the right, which now, being 
 
90 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 uncovered, is descending in order to get into the position 
 of fixation. In certain remarkable cases, however, the 
 deviafion of both eyes is up ( aiKitropia ), or of both eyes is 
 down (catatropia ) behind the screen. That is, if the right 
 eye deviates up behind the screen when the left is fixing, 
 the latter, as soon as the screen is shifted and the right eye 
 moves down to get into the fixing position, will move up. 
 In this case the visual lines, instead of remaining at a con- 
 stant angle, as in the case before cited, will approximate 
 until they become parallel, and will then diverge in the op- 
 posite direction. 
 
 Stevens (Ainiales (VornUstiqi(e, CXIII., 3, April, 1895,) 
 was the first to carefully study these cases and call them 
 by the names above given. ^ His view of them is that they 
 are due to the fact that initial elevation or initial depres- 
 sion of both visual lines ( i. e., an excessive sursumversion 
 or deorsumversion) is, in these anomalous cases, the nat- 
 ural state, to. which each eye tends to return when not 
 used for vision. But the condition may also, and perhaps 
 more plausibly, be ascribed to a spasm of sursumvergence, 
 or rather of the action opposed to sursumvergence (that, 
 namely, by which the visual lines, when vertically di- 
 verged, are brought together again). 
 
 X. 
 
 ANOMALIES OF ROTATION-MOVEMENTS. 
 
 Anomalous conditions, in which divergence or converg- 
 ence of the vertical meridians of the two corneae (other than 
 the physiological divergence which occurs when the visual 
 lines are converged) have been described by Savage. His 
 views, however, although urged with much plausibility, are 
 still far from being demonstrated. It seems likely that 
 these conditions, if they exist at all. are rare and of com- 
 paratively little significance. 
 
 •SclnveiKfrer, to hv sure (Arrh. f. A Hgenlicilk., XXIV., :i-4, 1894), 
 nuMitioiis sucli a case, l)Ut witlmiit atrfini)tin.<r any explanation of the 
 pliciioiiicnon. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 91 
 
 XI. 
 
 RECAPITULATION. 
 
 The conditions that I have sketched embrace all the dif- 
 ferent deviations, both manifest and latent, that are usu- 
 ally described. As the system of classification here pro- 
 posed differs radically from that generally employed, it 
 may be well, in a brief recapitulation, to show the points of 
 contact between the two. 
 
 The ordinary classification divides deviations into Out- 
 ward (or divergent). Inward (or convergent), and Vertical 
 (upward or downward). 
 
 These deviations may be due to the following causes: 
 
 SUMMARY OF DEVIATIONS. 
 
 I. Inward Deviations (Esophoria, Convergent Strabis- 
 mus) may be due to : 
 
 a. Over-action of one or both internal recti or of the 
 other adductors of the eye (superior and inferior recti). 
 
 h. Under-action of the external rectus or of the other 
 abductors (the obliques). 
 
 <•. Under-action of the center for producing divergence 
 movements (divergence -insufficiency). 
 
 d. Over-action of the center for producing convergence 
 movements (convergence-excess, which, in turn, may or 
 may not be due to excessive accommodative action). 
 
 e. Two or more of the above causes combined. 
 
 II. Outward Deviations (Exophoria, Divergent Strabis- 
 mus) may be due to: 
 
 a. Under-action of the internal rectus or of the other 
 adductors (superior and inferior recti). 
 
 h. Over-action of the external rectus or of the obliques. 
 
 c. Under-action of the center for producing convergence 
 movements (convergence-insufficiency, which, in turn, 
 may or may not be due to insufficiency of accommodative 
 action.) 
 
92 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 f/. Over-action of the center for producing divergence 
 movements (divergence-excess). 
 
 p. Two or more of the above' causes combined. 
 
 III. Upward and Downward Deviations (Hyperphoria, 
 Strabismus Sursumvergens and Deorsumvergens) maybe 
 due to: 
 
 a. Over-action of an elevator or depressor muscle. 
 
 h. Under-action of an elevator or depressor muscle. 
 
 r. Both of the above causes combined. 
 
 d. Sursumvergence- spasm, either uncomplicated or com- 
 bined with under-action or over-action of an elevator or 
 depressor. 
 
 IV. Mixed Forms (Hyperphoria combined with Exopho- 
 ria, Hyperphoria combined with Esophoria, and Esophoria 
 in one part of the field of view combined with Exophoria in 
 another) are frequent. 
 
 The differeiifiafion of these separate groups included un- 
 der the above general heads is readily made, for all have 
 well-marked signs which are detailed in the foregoing 
 sections (V.-VHI.). The diagnosis, indeed, can in almost 
 every case be made at once by applying the three broad 
 principles laid down in Section IV. (at the end of the re- 
 marks upon comitant and non-comitant deviations). 
 
 The liagnostic points indicative of the chief conditions 
 met with are recapitulated in the following table. 
 
 DIAGNOSTIC TABLE— TERMS EMPLOYED. 
 
 /*(■ (convergence near-point), the distance of the near- 
 point of convergence from the bridge of the nose, when 
 the object of fixation is carried toward the eyes in the me- 
 dian line. 
 
 /V ( Jl ), the distance of the near-point of convergence 
 from the bridge of the nose when the object of fixation is 
 carried directly toward the patient's left eye from some 
 point situated to the front and riuht of him (see Fig. 8 and 
 accompanying explanation). Pc (K) will, in this case, 
 denote the point at which the right eye sags off in eon- 
 
NEW CLASSIFICATION OF MOTOR ANOMALIKS- 93 
 
 vergence. Similarly, /V( L ) denotes the point at which the 
 left eye ceases to converge when the object is carried from 
 the left side directly toward the right eye. 
 
 Convergence-addnctiou, the power possessed by either 
 eye of moving inward in response to a convergence-stim- 
 ulus. Its measure is the Pc. 
 
 Associated adduction, the power possessed by either eye 
 of moving inward in performing associated parallel move- 
 ments, /. e., when the other eye is moving outward. It is 
 regularly greater than the convergence-adduction. 
 
 Priioti-convergence (the adduction of most) is the ability 
 to converge the eyes, when overcoming prisms, base out. 
 
 PfisD) -divergence {i\ie SihdiMction of most authors) is the 
 ability to diverge the eyes as measured by the degree of 
 prism, base in, which the eyes can overcome. This is said to 
 be i>roportionate to the amount of an exophoria or esophoria 
 when it equals 7 -f the exophoria or 7 — the esophoria 
 (for distance). 
 
 A. OUTWARD OR DIVERGENT DEVIATIONS. — (EXOPHORIA, 
 DIVERGENT SQUINT.) 
 
 I. Deviation and its evidences (exophoria, crossed di- 
 plopia) noticeably greater in some directions of the gaze 
 than in others. Pc abnormally remote. Pc (R) greater 
 or less than Pc and still more so than Pc (L). Excursion of 
 one eye and its field of fixation abnormally increased or re- 
 duced in some one direction, both for distance and near. 
 Under=Action of an Adductor or Over=Action of an Abduc= 
 tor riuscle. 
 
 Note— The diagnosis as to whether it is uuder-action or over- 
 action that is present may be made from the points detailed 
 under the head of diagnosis (4) in Section V. ; and the sped He 
 diagnosis of the muscle affected maybe made from the tables 
 of diplopia in same section ((i). As there stated, a crossed 
 diplopia (or an exophoria) which increases as the eyes are 
 carried to the right indicates weakness of some muscle of the 
 left eye or over-action of some muscle of the right eye; and 
 any exophoria which changes markedly in degree as the e>es 
 are shifted can be due only to under-action f)f an interims or 
 over-action of an externus. 
 
 II. Deviation and its evidences (exophoria, crossed di- 
 
94 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 plopia) sensibly the same in all directions of the gaze. 
 Pc (R) equals Pc (L). Excursion of both eyes and their 
 fields of fixation normal (at least for distance). 
 
 (II.) Deviation or exophoria sliprht for distaiici-. Marked for near 
 l)y all tests. Pc abnormally remote, ronvergenee-adtliu-tion 
 less than associated adduction (Graefe's test— see Section VI.). 
 Prism-diverg:ence not specially Ki'<"at (usually 8-10'^. or may be 
 subnormal). Prism-converuvnce subnormal and effected with 
 ditficulty. Convergence-lnsufficency. 
 Note. — The diagnosis between an iicconiinoddtire and a nou-nc- 
 commodative convergence-insufficiency will be made by refer- 
 ence to the etiology (see Section VI.) and by observing the 
 effect of glasses. The latter, if suitably adjusted, usually 
 relieve a trouble of purely accommodative origin. 
 (h.) Exophoria marked for distance; less for near (relations for 
 near may be nearly normal) . Pc normal, or nearly so. Prism- 
 divergence large (in typical cases disproportionately so: /. e., 
 it is greater than 7° -f the exophoria for distance). Prism- 
 convergence often normal and effected with facility. Diverg- 
 ence-Excess. 
 (c.) Exophoria marked for both distance and near. Pc abnor- 
 mally remote. Convergence-adduction less than associated 
 adduction (Graefe's test— see Section VI.). Prism-divergence 
 large, but not disproportionately so, compared with the amount 
 of exophoria. Prism-convergence usually reduced — often 
 greatly. Divergence-Excess with Convergence-Insuffi- 
 ciency. 
 Note.— The determination as to whether the divergence-excess 
 is secondary to the convergence-insufficiency, or is primary, 
 may be nuule by the differential diagnosis given in Section VII. 
 This condition is not always easy to diagnosticate from a 
 comitant deviation produced by under-action of one or both 
 interni, combined with over-action (due to compensatory 
 contraction) of the ejiterni. Moreover, it is not improbal)le 
 that a long-continued divergence-excess may give rise not 
 only to an insufficiency of ccmvergence, but to a weakness 
 of the interni j>cr se, due to their protracted inaction and to 
 the unfavorable conditions under which they work. 
 (d.) Exophoria marked for distance. For near, slight exophoria. 
 orthophoria, or esophoria. Pc normal or excessively near. 
 Convergence-adduction greater than associated adduction. 
 Prism-divergence large, sonu'times dispropin-tionately so. 
 Prism-convergence normal and readily ctt'ected. Divergence- 
 Excess with Convergence-Excess. 
 XoTE.— Tliesecases are sometitiics difficult to diagnosticatt' fn.m 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 95 
 
 those of anatomical pivpoiuli'i-auce of Itoth externi (struct- 
 ural deviation), combined with a convergence-excess. 
 The convergence-excess in these cases, being often accommoda- 
 tive, will frequently disappear upon the use of the proper 
 glasses. 
 (e.) Convergence-Insufficency with Divergence-Insufficiency. 
 (See Inward Deviations, B. II., d.) 
 
 III. Mixed conditions, in which the deviation increases 
 more or less in certain directions of the gaze, but in which 
 the phenomena noted under II. are likewise present 
 (combination of over-action or under-action of muscles 
 with a divergence-excess or a convergence-insufficiency) ; 
 and conditions in which, by the weakness of some muscles 
 and the over-action of others, a comitant exophoria or 
 divergent squint has been established, are not readily ana- 
 lyzed into their constituent factors. 
 
 B. INWARD OR CONVERGENT DEVIATIONS — (eSOPHORIA, CON- 
 VERGENT squint) . 
 
 I. Deviation and its evidences (esophoria, homonymous 
 diplopia) , noticeably greater in some directions of the gaze 
 than in others. Pc abnormally near. Pc(R) greater or 
 less than Pc and still more so than Pc(L). Excursion of 
 one eye and its field of fixation abnormally increased or 
 reduced in some one direction, both for distance and near. 
 Under=Action of an Abductor or Over=Action of an Adduct- 
 or Muscle. 
 
 Note. — For the specific differentiation see Section V., remarks 
 on diagnosis, (4) and (G). As there stated, a homonymous 
 diplopia (or an esophoria) which increases as the eyes are 
 carried to the right, indicates weakness of some muscle of 
 the right eye or over-action of some muscle of the left eye ; 
 and an esophoria which changes markedly in degree as the 
 eyes are shifted can be due only to under-action of an ex- 
 ternus or over-action of an internus. 
 
 II. Deviation and its evidences (esophoria, homonymous 
 diplopia) sensibly the same in all directions of the gaze. 
 Pc(R) equals Pc(L). Excursions of both eyes and their 
 fields of fixation normal (at least for distance). 
 
 (a.) Esophoria marked for distance: slight or replaced by ex- 
 ophoria for near. Pc normal. Convergence-adduction equal 
 
96 NEW CLASSIFICATION OF MOTOR ANOMALIES. 
 
 ti> oi- iiKnc ()!• less tliaii tlic associated adduction. l*rism-di- 
 \('ry-ciic(' low (may l)c disitroportioiiatcly so. /. v.. is less than 
 7 — the esoi)horia for distain-e). l'i'isiii-coiiver»i-encc iioniial, 
 or often suhiiornial. Divergence-Insufficiency. 
 
 (h.) E.soplioria slifrht for distance : more for near. Pc exces- 
 .sively near (less than 1 inch). Converjarence-adduction may be 
 greater than associated-adduction. I'rism-diverg:ence ncn-mal, 
 or Init slijriitly sul)nornial (never disproportionately low). 
 Prism-con verufence normal. Convergence-Excess. 
 
 Note. — The diagfiiosis between an incDiiniKKtattn- and ;i non-ac- 
 cuiinnodntire convergence-excess will be made by refei'ence 
 to the etiology (see Section VI.) and by observing the 
 eltect of the long-continued use of glasses (or of atropine), 
 which in most cases will relieve a difiieulty of purely accom- 
 modative origin. 
 
 (c.) Esophoria marked for distance and near. Pc excessively 
 near. Convergence-adduction e(juals oris greater than asso- 
 ciated adduction. Prism-convergence low in proportion to 
 degree of esoi)horia for distance, or disproportionately low. 
 Prism-convi-rgence normal. Divergence-Insufficiency and 
 Convergence-Excess. 
 
 NoTK. — The determination as to whether the divergence-insuf- 
 ticiency is secondary to the convei-gence-excess,or is primary, 
 maybcmade from the dift'erential diagnosis in Section VII. 
 
 {(I.) Esophoria marked for distance; exophoria (of mon- than 4 
 or 5°) for near, noticeable by all tests. Pc abnormally remote. 
 Convergence-adduction less than associated adduction. Prism- 
 convergence low. Prism-convergenci' sul)normal ami hainl to 
 tram. Divergence-Insufficiency with Convergence-Insuf- 
 ficiency. 
 
 (e.) ( 'on rnycnce- J-'Jjvess irith J)i rcn/cii cc- K.rccss . 
 (See Outward Deviation, A. II., d). 
 
 IIL Mixed conditions, analogous to those given under 
 Outward Deviations III. exist, but are hard to analyze. 
 
 C. VERTICAL DEVIATIONS — (HYPERPHORIA, STRABISMUS SUR- 
 SUMVERGENS AND DEORSUMVERGENS.) 
 
 I. Hyperphoria or its evidences (vertical diplojiia) in- 
 creasing in some one direction of the gaze. 
 
 ((I.) Hyp«'ii.h(.ria increasing as the i-ycs arc carrictl upward. 
 
 Over-Action or Under-Action of an Elevator IMuscle. 
 (h.) llyi»eri»horia increasing as the eyes are carried downward. 
 
 Over-Action or Under-Action of a Depressor Muscle. 
 
NEW CLASSIFICATION OF MOTOR ANOMALIES. 97 
 
 NoTK.— F'or tlic spccilic diafiiiosis of the imisclc anVctcd see 
 Section V., remarks on diagnosis (4 and 0). 
 II. Hyperphoria the same in all parts of the field (com- 
 itant hyperphoria, comitant vertical strabismus). 
 
 (a.) Due proI)a))ly in most eases to under-action of an elevator or 
 depressor, with over-action of on*' or more antafj-onislic mnscle. 
 Mixed Cases. 
 
 (b.) Sometimes to equal \ertieal diver>;enee of the visual lines 
 (see Section VIII). Sursumvergence-Excess. 
 
 CONCLUSION. 
 
 One who proposes a new classification must be pre- 
 pared to defend his position by showing that it subserves 
 some useful purpose. That this is the case with the one 
 propounded in the preceding pages seems to me proved by 
 the following reasons : 
 
 1. The classification is based upon physiological facts 
 instead of mere external appearances. 
 
 2. Its divisions correspond to natural groups, distinct in 
 nature and symptoms, and frequently requiring widely 
 different methods of treatment. 
 
 3. The groups so made are readily distinguishable in 
 practice by the signs they afford. 
 
 4. We can by means of the scheme here presented ana- 
 lyze the frequently occurring mixed forms, and from our 
 knowledge of the nature and tendency of the component 
 lesions determine to which of the latter our treatment shall 
 be addressed. 
 
INDEX. 
 
 Abducting power of the obliques and 
 external rectus, auionnt of. It, 15. 
 
 Alxluction (in proper sense of term, 
 licnolini; the power possessed by each 
 eye of moving outward), 9. 
 
 Abduction (in its ordinary sense of mut- 
 ual divergence of the visual lines). 
 See Divergence and Prism- Dioerf/eiice. 
 
 Accommodation always brought into 
 play when convergence is exercised by 
 prisms, Jl: this shoi-.ld be taken into 
 account in making muscular tests, .'^S. 
 
 Acct)mmodative convergence-excess, 79. 
 
 .-Accommodative converg e n c e - i n s u ffi- 
 cieucy, 73. 
 
 .Adductiug power of the superior, infe- 
 rior, and internal recti, amount of, 
 14, 15. 
 
 Adduction (in proper sense of term, 
 denoting the power possessed by each 
 eye of moving inward), 9; varieties 
 (convergence - adduction, associated 
 adduction), 93. 
 
 Adduction (in its usual sense of mutual 
 convergence of the two visual lines). 
 Sec Concergence and Pritmconcer- 
 genre. 
 
 .•\natropia, 6S, 9U. 
 
 Antagonists, associated, 19, 2U, 29. 
 
 Antagonists, direct, 7. 
 
 Associated adduction, 93. 
 
 Associated antagonists, 19, 20, 29. 
 
 Associated convergent movements, tests 
 for, 36. , , , 
 
 As.sociated parallel movements, table of, 
 1719; extent of, 20; centers for, 22; 
 tests for, 35; anomalies of, 67. 
 
 Association centers. 22. 
 
 Asthenic exophoria. 77. 
 
 Asthenic vertical orthophoria. 6s. 
 
 B. 
 
 Binocular fixation, field of, 2u; tests for, 
 
 .3U, 35. 
 Binocular single vision, field of, 2C; tests 
 
 of, .35. 
 
 c. 
 
 Catalropia, 6K, 90. . 
 
 Choreiform spasm of associated obliciue 
 movements, 69. 
 
 Clissification of ocular deviations, upon 
 what based, 42, 43; author's pro- 
 posed scheme, 44; previ.iiis scl;< lues, 1. 
 
 Comitant and non-coiin(;int (l.Mations, 
 ^6etseci.; laws govtrnmi; U.in-lnrma- 
 tion of, 4H; character ..1 -rm ii nu)ve- 
 ments in, .33. 
 
 Comitant hyperphoria. 60.9/ . 
 
 Compensation of deviations, law ot, 4h, 
 
 Concomitant. See Comitant. 
 Congenital deviations, characters ol bh. 
 Constant squint, 44. 
 Convergence, exercise ol by prisms, -J; 
 
 exercise of, produces sjjasm of accom- 
 modation, 24, 3S; maximum i>ower of, 
 22 ; test for, .36. 
 
 Convergence-adduction, 93. 
 
 Convergence-anomalies, 71. 
 
 Convergence-e.vcess. 7S; differential di- 
 agnosis of, 96; with secondary diver- 
 gence-insufficiency, diagnosis of, S4, 96. 
 
 Convergence-insufficiency, 72; charac- 
 ters, 72; non-accommodative, 73; ac- 
 commodative, 75; course. 75; compli- 
 cations, 77. <S7. 94; symptoms. 77, 
 diagnosis, S7, 94; treatment, 77. 
 
 Convergence-movements, 22. 
 
 Convergence near-point, 22, 92; determi- 
 nation of, .16. 
 
 Convergence-paralysis, 71. 
 
 Convergence-spasm. 3S, 7.s. 
 
 Convergence of the vertical meridians of 
 the corner, 26; abnormal, 90. 
 
 Crossed diplopia, 31. 
 
 Crossed parallax. 34. 
 
 D. 
 
 Deorsumduction (in proper sense of 
 term), 10. 
 
 Deorsumversiori, how effected, IS; par- 
 alysis of, 6S. 
 
 Depressing power of inferior rectus and 
 superior oi)lique. amount of, 14. 
 
 Deviations, classification of, 1, 42-46; di- 
 agnostic table of, 92; inward, 91, 95; 
 mixed forms, 92, 95, 96. 97; outward, 91, 
 63-95: transformation and evolution of 
 law of. 48, 49; vertical, 92, 96. 
 
 Dextroversion, how effected, 17; par- 
 alysis of, 67; spasm of, 6.S. 
 
 Diagnostic table of deviations, 92; of 
 muscular paresis and spasm based on 
 the double images, 61-63. 
 
 Diplopia, how brought out and differen- 
 tiated. 31; how measured, 31; method 
 of recording, 39; transient, indicating 
 physiological limitation^of field of 
 single vision, 35; varieties (crosse<l, 
 left, homonymous, right, etc.), .^0, 31; 
 table of, in muscular paralysis and 
 spasm, 61-63. 
 
 Diplopia-test, 30, 35, 36, .W. 
 
 Divergence (or Diverging power). 24; 
 nature of. 25; produced by pri.sms. 24. 
 .3S; of slight amount, physiological for 
 near points. 36; tests for. .^S. 
 
 Divergence-excess, S6, 94. 
 
 Divergence-insufficiency. S3. 96. 
 
 Divergence of the vertical meridians of 
 the cornea;, 27; pathological. 90. 
 
 Donders' lawdiagramatically illustrated. 
 
 Downward associated movements. See 
 
 Deormmveruon. 
 Downward deviations, 92, 96. 
 Dynamic association-tests, .Ui. 
 Dynamic disassociation-tesls, .30. 
 
 I'Uectricity, <►). 
 Klevating power of 
 
INDEX. 
 
 99 
 
 inferior oblique, amount of, It. 
 
 Kquilibrium test, .n, ,1S, 36, .V). 
 
 Ksophoria, 3J; accommodative. 79, 
 sthenic, 79; varieties of, according to 
 the new classification, 91; varieties of, 
 how differentiated, 95. 
 
 Kxophoria, 3.'; asthenic, 77; varieties of. 
 according to the new classification, 91 ; 
 varieties of, how differentiated, 93-95. 
 
 Kxteraal rectus, action of. 6, 9-11. 17-19; 
 action of, how modified by the verti- 
 cally acting muscles, 2s. 
 F. 
 
 Field of binocular fi.Yation. Ju. 
 
 Field of binocular single vision, 2u; con- 
 centric contraction of. 3S. 59; how 
 mapped out. ,^5, 39; pathological and 
 accidental limitation of, as shown by 
 the varieties of diplopia occurring, 35; 
 physiological limitation of. 35. 
 
 Field of (monocular) fixation, 12, 40; 
 diagram of. 26. 27;. how limited in 
 muscular paralysis, 29. 59; how map- 
 ped out, 35; measurements of. 12. 13. 
 
 Fixation-test, 30, 35, .36. 
 
 Fixing eye, how to determine the. 3?!. 
 
 Fusion near-point. See Convergence 
 near-point. 
 
 H. 
 
 Heteronymous diplopia, 31. 
 
 Heteronymous parallax, 3-t. 
 
 Heterophoria. 3, 43; insertional. 51; 
 spastic. 60; structural, 51. 
 
 Heterotropia. 3, 44. 
 
 Homonymous diplopia, 3li. 
 
 Homonymous parallax. 34. 
 
 Hyperkineses, 44. 
 
 Hyperphoria, 31, 59; comitant, 60, 97: 
 varieties of, classified according to 
 external character, S9; varieties of. 
 classified according to etiology. 92; 
 varieties of, how differentiated, 96. 
 
 Hypertropia, 89. .See also Strabtsnms 
 sursumverffens and Struhismus deorsum- 
 vergens. 
 
 Hypokineses. 43. 
 
 I. 
 
 Individual muscles, actions of. 6; an- 
 omalies of. 49; slight cases of anomal- 
 ies of, 59. 
 
 Inferior oblique, action of. 6. 9-11, 17-19; 
 field of action of, graphically shown, 
 26; and superior oblique, combined ac- 
 tion of, 28; and superior rectus, com- 
 bined action of. 26, 27. 
 
 Inferior rectus, action of, 6, 9-11, 17-19; 
 field of action of, graphically shown. 
 27; and superior oblique, combined 
 action of, 27; and superior rectus, 
 combined action of, 27. 
 
 Inspection, 30, 35, 36, 39. 
 
 Insufficiency.discoveryof, 3; faulty use of 
 term, 3. See also Heterophoria. 
 
 Intermittent squint, 44. 
 
 Internal rectus, action of. 6, 9-11, 17-19; 
 action of, how modified by that of the 
 vertical muscles, 28. 
 
 Innervational deviations. 52. 
 Insertional squint or heterophoria. 49, 
 
 51. 
 Inward deviations, varieties of, classified 
 according to etiology, 91; varieties, 
 differential diagnosis of, 95. 
 L. 
 
 Latent squint, 44. 
 
 Law of comitance, 4S, 49. 
 
 Left associated movements. .See Sinis- 
 irorersion. 
 
 Left diplopia. 31. 
 
 Left parallax. 31. 
 
 Left sursumvergence. 38. 
 
 Listing's law, diagrammaticallv illus- 
 trated, 29. 
 
 M. 
 
 Maddox rod. 31 (note). 
 
 Manifest sciuint. 44. 
 
 Mixed forms of deviation, 92, 95, 96, 97. 
 
 -Mixed nystagmus. 70. 
 
 Movements, binocular, five classes of, 
 15, 16; with unimportant exceptions 
 subserve binocular fi.xation, 15; de- 
 scription of, 17-29. 
 
 Movements, monocular, 7-14; extent of, 
 11 ; can be performed in all directions, 
 8; tabular view of, 9-11; diagrammatic 
 representation of, 26-29. 
 
 Movement of redress, 33. 
 
 Muscles of eye. combined actions of. 27, 
 2.S; table of action of, 6. 
 
 N. 
 
 Near-point of convergence, 22, 92; de- 
 termination of. 36. 
 
 Nerve-centers governing individual ocu- 
 lar muscles, S; for associated parallel 
 movememnts. 22; for movements of 
 convergence, 22. 
 
 Neurasthenia, enfeebled action of eve- 
 muscles in, 59. 
 
 Non-accommodative convergence - ex- 
 cess, 79. 
 
 Non-accommodative convergence-insuf- 
 ficiency, 73. 
 
 Nou-comitant deviations, 46 et seq. , 
 character of screen-movement in, 33. 
 
 Nystagmus, bilateral (or ordinary), 69; 
 unilateral, 67. 
 
 o. 
 
 Obliques, combined action of, 28. 
 
 Operation in cases of convergence-ex 
 cess, S3; in convergence-insufficiency, 
 78; in divergence-excess, 88; in diver- 
 gence-insufficiency, 86; in muscular 
 paresis or spasm, 64-66. 
 
 Outward deviations, varieties of, classed 
 according to etiology, 91; varieties of, 
 differential diagnosis, 93-95. 
 
 Over-action and underaction, differential 
 diagnosis of, 59. 
 
 P. 
 
 ranaroma-asthenopia. Panorama head- 
 ache, 85. 
 
 Parakineses, 44. 
 
 Parallax, 34; measurement of, .VS. 36, 39; 
 varieties. 35. 
 
 Parallel squint. 71. 
 
 Paralysis of associated parallel move- 
 ments, 67 
 
 Paralysis of convergence, 71. 
 
 Paralysis of ocular muscles. 49. 52-67; 
 differentiation of, from spasm, 58; diag- 
 nosis of, by means of double images. 
 til-63; limitation of field of fixation and 
 character of diplopia in. graphically 
 represented. 29. 
 
 Paretic esophoria. 95. 
 
 Paretic exophoria, 93. 
 
 I'aretic hyperphoria. 96. 
 
 Paretic squint. See I'urali/sis of ocular 
 nutacien. 
 
 Periodic squint. 44. 
 
 Phorometer, ?,2. 
 
 Prisms, seldom giving precise measure- 
 
100 
 
 INDEX. 
 
 iiient of (lijilopia, 31 (note); when used 
 as an exercise. Kivin^ Kood results in 
 converKence-insufficiency. 7K. hut of no 
 avail in converKence excess or diver- 
 trence-insiifficiency, S3, S5; when em- 
 p'.oyed for constant wear, sonulinics 
 serviceable in anomalies of the indi- 
 vidual iniiscles and particularly in 
 vertical deviations. 64, but niiscliiev- 
 ous in convergence-insufficiency, .on- 
 vergence - excess, and divergence- 
 insufficiency. 78, «3, 85. 
 
 Prism-convergence, 23, 39. 89. 
 
 I'rism-divergence, 24, 38, 39, 93. 
 
 Pseudo-esophoria, 79. 
 
 R. 
 
 "Relaxation" of the muscles often really 
 a condition of active contraction, 2^. 
 
 Right as.sociated movements. ,See Ocx 
 irorersioii. 
 
 Right diplopia, 31. 
 
 Right hyperphoria, 31. 
 
 Right parallax. ,34. 
 
 Right sursumvergence. 38. 
 
 Rotation movement.s. .See TorsU ii - 
 movements. 
 
 s. 
 
 Screen-test, 3.', 35, .36, 39. 
 
 Sinistroversion, how effected, 17; paraly- 
 sis of, 67; spasm of. 68. 
 
 Spa.sm of associated parallel movements. 
 68. 
 
 Spasm of convergence, 78. 
 
 Spasm of ocular mnscles, 52-55; diag- 
 nosticated from paralysis, 58; slight 
 cases of, 59; diagnosis of. by means of 
 double images, 61-63; treatment, 6,3-67. 
 
 Sp.Tstic esophoria, 95. 
 
 .Spastic exophoria, 93. 
 
 Spastic heterophoria, fin. 
 
 Spastic hyperphoria, 96 
 
 Spastic squint. See Sptiniii of ontUir 
 muxcles. 
 
 .Static tests. MK 
 
 Stevens' classification. .^: phorunielev, 
 32; sphere, 31 (note): theory (jf ana- 
 tropia and catatropia, 9ii, 
 
 Sthenic esophoria, 79. 
 
 -Strabismus accommodative. 79; con- 
 stant, 44. 
 
 Strabismus convergeus, varieties of. 
 classed according to etiologj', 91 ; 
 varieties of, how differentiated, 95. 
 
 Strabismus deorsumvergens, 5, 7, 89, 8.'; 
 varieties of. how differentiated. 96. 
 
 Strabismus divergens, varieties of, ac- 
 cording to etiology, 91; varieties of, 
 how differentiated, 93-95. 
 
 .Strabismus, innervational, 5-'; intermit- 
 tent, 44; latent, 44; manifest, 44; mus- 
 cular, .50; parallel 71; paretic (see 
 I'arnhjsis of omliir mnxcli'S) ; periodic. 
 II; spastic I see Spa.im of ocular ^mus- 
 clen) ■ strucl\iral. l'i-51. 
 
 StrabTsmiis sursumvergens. 57, 89, 92; 
 varieties of, how differentiated, %. 
 
 Structural squint and heterophoria, 49- 
 51. 
 
 Strychnine, 6-1. 
 
 Superior obliciue, action of, 6, 9-11, 17-1''; 
 field of iiction graphically shown, 26; 
 ;in<l inferior oblique, combined action 
 of, 28: a'nd inferior rectus, combined 
 action of, 27. 
 
 .Superior rectus, action of. «'. 'i-ll. 17 1'^; 
 field of action of. graphically shown. 
 26; and inferior oblique, combined ac- 
 tion of, 26. 27; and inferior rectus, 
 combined action of. 27. 
 
 Sursumduction (in proper sense of term, 
 uuaning absolute movement of eye 
 upward). lU. 
 
 Sursumduction (in ordinary sense of 
 term, meaning vertical divergence 
 of the visnaUlines).' .See -Awrsimrer- 
 geme. 
 
 Sursumvergence. 26; anomalies of. 8s; 
 tests for. 3s. 
 
 .Sursumvergetice-excess. 88. 97. 
 
 Sursumvergcnce-insufficiency. 88. 
 
 Sursumversiou, how effected. 17; para- 
 lysis of. 68. 
 
 Swivel-movements. See Tursioii move 
 iiients. 
 
 T. 
 
 Table of actions of individual muscles, t: 
 
 Table of associated antagonists. 20. 
 
 Table of associated parallel movements. 
 17-19. 
 
 Table of deviations classed according to 
 etiology. 44-46. 
 
 Table of deviations classed in the usual 
 way as outward, inward, and vertical, 
 with the etiological diagnosis of each 
 variety, 92-97. 
 
 Table of diplopia in muscular paresis 
 and spasm. 61-63. 
 
 Table of the movements of each eye and 
 of the part that the different muscles 
 take in producing them, 9-11. 
 
 Tests. .^O-^O: of associated convergent 
 movements 36; of associated parallel 
 movements. 35; for binocular fixation. 
 30. 35; of binocular single vision. .35: 
 of convergence. 36; diplopia. 30. 35, .36, 
 .39; of divergence. 38; equilibrium. 31. 
 ,35. .36, .39; fixation, .30. .35. .36; inspec- 
 tion, .30. 35. .36. .39; parallax. .34. .39; 
 phorometer, 31, ,35. .36, ,39; screen, 32. 
 ,'^5. ,36. .39; static. .30; of sursumverg- 
 ence. .32. 40. 
 
 Tonic treatment. 64.7s. 
 
 Torsion-movements produced by indi- 
 vidual muscles. 6; produced in the va- 
 rious monocular movements. 9-11 : 
 produced in the various binocular 
 movements. 17-19; graphic representa- 
 tion of individual and combined 
 effects of the muscles upon. 2": amount 
 of, how determined. 14; anomalies of. 
 90. 
 
 u. 
 
 ->ocialed movement.' 
 
 See 
 
 rpNMMil iU\ iiitiuns. varieties of. classed 
 anonlini.; I. .etiology. 89, 92; varieties 
 of, liow differentiated. 96. 
 
 V. 
 
 Vertical deviations, varieties of. classed 
 according to etiology, .89, 92: varieties 
 of. how differentiated, %. 
 
 Vertical diplopia, 31. 
 
 w. 
 
 Work done by the different mu.scle.s in 
 moving the eye. l.v 
 

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