THREE CASES OF STRABISMUS WITH ANOMALOUS DIPLOPIA. AN ORIGINAL AND ACQUIRED FIXA- TION-SPOT IN THE SAME EYE. CHARLES HERMON THOMAS, M. D. FELLOW OF THE COLLEGE OF PHYSICIANS OF PHILADELPHIA. MEMBER OF THE AMERICAN OPTHALMOLOGICAL SOCIETY. FORMERLY SURGEON TO PHILADELPHIA HOSPITAL, ETC. REPRINTED FROM AMERICAN OPTHALMOLOGICAL SOCIETY TRANSACTIONS, 1894. WITH THE COMPLIMENTS OF CHARLES HERMON THOMAS, M. D. 1807 CHESTNUT STREET PHILADELPHIA, PA. THREE CASES OF STRABISMUS WITH ANOMALOUS BIPLOPIA. AN ORIGINAL AND ACQUIRED FIXA- TION-SPOT IN THE SAME EYE. CHARLES HERMON THOMAS, M. D. FELLOW OF THE COLLEGE OF PHYSICIANS OF PHILADELPHIA. MEMBER OF THE AMERICAN OPTHALMOLOGICAL SOCIETY. FORMERLY SURGEON TO PHILADELPHIA HOSPITAL, ETC. REPRINTED FROM AMERICAN OPTHALMOLOCICAL SOCIETY TRANSACTIONS, 1894- THREE CASES OF STRABISMUS WITH ANOM- ALOUS DIPLOPIA: AN ORIGINAL AND AN ACQUIRED FIXATION-SPOT IN THE SAME EYE. 15Y CHARLES HERMON THOMAS, M.D., PHILADELPHIA, PENNA. The development in certain cases of strabismus, in the squinting eye, of a spot to a great extent “identical” with the macula lutea of the straight eye has been described by Swanzy, Berry, and others. In the cases here presented attention is asked to the existence of two fixation-spots in the deviating eye — one the normal macula, used in monocular fixation only, and the other an acquired fixation-spot to which reference is made by the patient in binocular fixation only. The first two cases were divergent strabismus, and were studied with me by my friend, Dr. Edward Jackson, before and after operation ; the third was a case of convergent squint. All of them were treated by operation, successfully as regards cos- metic effect; but in none was orthophoria attained. In none, it may be added, did the ophthalmoscope reveal anything char- acteristic of the condition under consideration. E. M. F., female, aged 11 years. Referred to me by Dr. W. H. H.Githens. V. = R. and L. —6/6 -f- .H =.50D. Marked divergent strabismus — intermittent. Generally fixes with the right eye, but occasionally with the left; is able to continue in binocular fixation for a considerable time. With the eyes in a position of divergence, under a light-red glass, there is homonymous diplopia, requiring prisms io° with their bases out to correct. Prisms aggregating 350 with their bases in arrest movements of recovery under the cover test — not complete cessation of all movement, but rather an irregular vibratory movement from side to side, lasting a few seconds, and aptly termed by my associate, Dr. Schneideman, a “search ” movement. With vertical prisms, and also with red glass, the eyes remaining in apparent divergence, responses as to the char 4 Thomas : Strabismus with Anomalous Diplopia. acter of the diplopia are contradictory, changing from homony- mous to hetcromonymons. P. P. of convergence, four inches. Apparent binocular fixation while reading; squint equals 250 to 30° prism measure. Tenotomy of left externus complete; result, abolition of deformity ; but there remained recovery from divergence neu- tralized by prism 170 base in and diplopia as produced by red glass is crossed, requiring prisms of like strength to correct. The strabismus being no longer manifest, and in its latency giving no discomfort, by wish of the patient, further operation was postponed. The alternating responses as to the character of the diplopia showed that the patient was referring at one instant to the macula and at another to the false fixation-spot, thus proving that the latter had not become predominant. After the opera- tion the macula was alone referred to and the false spot aban- doned, as was shown by the agreement between the responses of the patient and the position of the eye. C. E. H., aged 14, male. Vision, R. 6/8 and L. 6/20; emmetropic. Has divergent strabismus, fixes with the right eye, but on covering this eye, fixes centrally with the left and can continue such fixation for a time after removing the cover from in front of the right eye, which, meantime, remains in divergence. Tenotomy, left externus completely divided; result, lessened divergence, but it is still marked under cover test, notwithstand- ing which, he now has homonymous diplopia. Three days later, the condition of divergence under cover continued, except at the outer limit of the field of fixation on the left side — the side of the severed tendon — where there is recovery from con- vergence under the cover test. The diplopia has disappeared, except at the outer limit of left field, where it is homonymous. With the red glass, however, there is homonymous diplopia over the entire field. Though there is manifest divergence, the vertical prism test — phorometer — indicates y° esophoria. At a subsequent examination divergence continued, requir- ing prisms of 140 base in to abolish visible recovery under the cover test. At the same time prisms base in — even 2° or 30— Thomas: Strabismus zvith Anomalous Diplopia. 5 produced homonymous diplopia, making it plain that further correction of the exotropia would result in constant diplopia and, therefore, that the attainment of perfect parallelism was impracticable. It may he thought that an attempt ought to have been made by perfect adjustment of the muscular balance to compel the use of the normal macula to the entire exclusion of the false fixation-spot. But the immediate effect of further correction, as shown by the use of prisms base in, would have been the pro- duction of an annoying diplopia (homonymous). This might or might not have been overcome in time by education ; the prob- ability of such result under all the circumstances involved being to my mind unfavorable. E. P. C., aged 30, bank clerk, V.= R. 6/6 + L. 6/10; wear- ing low hyperopic correction. Has convergent strabismus, very marked ; left eye deviating. Tenotomy, left internus, complete section. Left externus advanced. Immediate result, improvement in degree of strabis- mus. Manifest limitation of movement inward with left eye. Two weeks later, convergent strabismus of considerable amount remains; large recovery from convergence under cover test, but shows cxophoria, Maddox rod test, 20°, but with prisms 2o' base in, there is wide crossed diplopia. With prisms 20° base out, movement of recovery is abolished, and a search movement is seen, about equal in either direction. Tenotomy of right internus, complete section. Result, abolition of apparent strabismus, slight recovery from divergence under cover test (6°) and wide crossed diplopia (30°) under red glass test. The left eye being amblyopic and never having participated in binocular vision, the patient is not annoyed by diplopia, which, indeed, can only be elicitated under special conditions. Thus, following operation the eyes in convergence to the amount of 20°, there was at the same time present an Ex. of a like amount (20°). The correction of this Ex. by prisms base in, instead of giving single vision, as was naturally to be ex- pected from it, resulted instead in crossed diplopia. The operation, by giving to the eyes a position more nearly 6 Thomas : Strabismus with Anomalous Diplopia. parallel than they had formerly held, disarranged the relation of the two retinae to one another with the results here seen. Here, again, the association of convergence with exophoria is only explicable by the assumption of an acquired fixation-spot in addition to the normal macula. In all these cases, when either eye was used alone, the see- ing eye was directed centrally, i. e., either eye used alone fixed with the normal macula. On the other hand, when the two eyes were used simultaneously, the diplopia, if noticed, was seen to relate to the acquired fixation-spot. This was particu- larly true of the latter two cases. In the first case the alternat- ing character of the diplopia showed that the patient could refer indifferently either to the mascula or to the acquired spot. In view of the conditions present in the cases here described, the following inferences appear justified: (1) Binocular vision — ceil cyclopienne — involves an addi- tional cerebral function above and beyond that involved in monocular vision. (2) That corresponding points of the two retinae are in binocular fusion correlated with the functional fixation-spot, whether that spot lies in the normal fovea centralis or not. (3) That suppression of the macular image during the act of binocular vision may take place, the image upon the false fixation-spot only being regarded while the macula has its usual predominance when the eye is used alone, i. 7 Chestnut Street.