Strabismus, or Crossed Eyes. HOW SHALL WE TREAT THEM? BY FRANCIS VALK, M. D., Professor of Diseases of the Eye, New York Poet-graduate School, etc. REPRINTED FROM THE Neto ¥ovft jfHetocal Sournul for November 2$., 189 f Reprinted from the New York Medioat Journal for November 189 f STRABISMUS, OR CROSSED EYES. HOW SHALL WE TREAT THEM?* By FRANCIS VALK, M. D., PROFESSOR OF DISEASES OF THE EYE, NEW YORK POST-GRADUATE SCHOOL, ETC. \ All physicians may at times be called upon for an opinion in reference to the convergence of the eyes of their little patients, so I have thought that the suggestions of this paper may be of service to the society; and since the discussions of the profession in reference to squint are, ac- cording to my observations, somewhat uncertain and mis- leading, I therefore wish, if possible, to correct them from my own clinical experience. The thoughts contained in this paper were most forci- bly suggested to me by the following quotation from Dr. W. B. Johnson's excellent article on Amblyopia from Sup- pression of the Visual Image, which paper was read before the American Ophthalmological Society in the summer of 1893. Dr. Johnson says: "The natural tendency of the visual centers is to relieve themselves of the diplopia, which is an * Read before the Medical Society of the County of New York, May 28, 1894. Copyright, 1894, by D. Appleton and Company. 2 STRABISMUS, OR CROSSSED EYES. offending condition, and relief is attained by a gradual loss of physiological sensibility through psychical exclusion of the vision of one of the eyes. The selected eye may or may not have diminished visual acuteness due to a greater refractive error than the fellow eye, each eye, however, generally having a hypermetropia of a greater or lesser degree, which is almost always present, and is undoubtedly an important aetiological factor in the production of con- vergent squint." I have reported his words thus fully, as I find here two very interesting questions to answer : First, Is there, as a rule, loss of physiological sensibility through psychical ex- clusion of the vision ? and secondly, Is hypermetropia an important factor in the causation of squint ? In discussing this subject I wish to present some views of my own in relation to crossed eyes from my obser- vations both in private and clinical work ; not that they may differ very materially from those previously accepted, but that I may separate the cases of convergent squint, when there is no paresis of the external muscular apparatus, into two great classes-operative or non-operative. In these two divisions we may place all the cases that come under our care and treatment, thereby deciding the relative value of glasses or of an operation. There seems to be an impression among the profession that the vision of amblyopic eyes can be restored with binocular fixation under certain conditions. And the ques- tion arises, Is this true in all cases, or only in a certain number, or under certain conditions of refraction ? It seems to me that if this fact can be established in any one case, then it should hold good in all. In answering this we shall also find the answer to the quotation above stated. Fuchs, in the last edition of his work, gives the aetiol- ogy of squint as follows : " Strabismus is, therefore, the STRABISMUS, OR CROSSED EYES. 3 result of the combined action of two factors-diminution of the visual power of one of the eyes and a pre-existing dis- turbance of the muscular equilibrium. According as the latter factor consists in a preponderance of the internal or the external ocular muscles, a convergent or divergent squint is produced." The same ideas have been advanced by Stilling and also by Swan Burnett, and these I propose to follow in a certain measure to be explained. Leaving out, then, all pathological conditions and con- sidering these questions as they relate to squint per se, as usually seen in the office and at the clinics, let us define the conditions as indicated in our cases. I would first define amblyopia as an unknown condition occurring generally in the non developed or hyperopic eye, in which, without any visible evidence of an abnormal condi- tion, there will be a want of power in the retinal elements, either existing in the nerve fibers or its terminal elements in the retina, and by which they can not appreciate small images formed on the retina and thence to be conveyed to the brain. Consequently there is no fault in the dioptric media, causing diminished visual acuteness due to refractive error, nor is there psychical exclusion of the vision, but that the amblyopia is congenital. Why this condition, as above stated, should occur only in the one eye and not in the other I am unable to explain. It is simply a clinical fact. On the other hand, if we do have a condition of perfect visual acuteness in both eyes, but that the rays of light can not be focused on the retina without excessive accommo- dation-and by that condition the stimulation of excessive convergence (relative hypennetropia)-then we shall have one eye converging more than its fellow. Now, we have suppression of vision in the squinting eye that in time will produce diminished vision, due either to a refractive error 4 STRABISMUS, OR CROSSED EYES. or to psychical exclusion ; but this may be and will be re- stored as soon as the demand for excessive convergence and accommodation is removed by the correction of any refractive error by glasses. There can be no diplopia under these conditions, be- cause, while the image is perfect in the fixing eye, the rays from the object must fall upon the peripheral parts of the retina in the squinting eye, there forming only a diffused image that will be suppressed. Again, the rays which fall upon the macula coming from a plane different from that of the object or point to which the dioptric apparatus may be adjusted, these rays can only form a diffuse image that is not conveyed to the visual centers. Hence there is no stimulation of the physiological functions of the nerve elements at the macula for certain periods of time, and consequently, when at first this func- tion is resumed by the usual tests, the vision will be found reduced, but will be rapidly restored under proper condi- tions. In the {etiology of squint I think these explanations may suffice ; but is there a disturbance of the muscular equilibrium ? Or is the squint due simply to the normal conditions of adduction and abduction ? And does not an exception to the rule cause divergent squint ? Let us first divide our cases into two great classes or divisions, according to their observed frequency: First, squint associated with congenital amblyopia, and, secondly, squint due to relative hyperopia, with temporary suppres- sion of the visual image. In these two classes I think we can readily place all our cases of squint, and if so, then the method of treatment, either operative or otherwise, will be readily and clearly indicated from the beginning to the final parallelism of the optic axes. If we take up our first class of cases I think STRABISMUS, OR CROSSED EYES. 5 we can at once answer the question as to the aetiology. I do not believe hypermetropia is in any way an aetiological factor in the causation of this squint, though always asso- ciated with it. Let me illustrate this: A child is born of perfectly healthy normal in all respects, the visual axes per- fectly parallel, and the power of the external muscles prop- erly proportioned. But there is present a condition of amblyopia that, I believe, is due to a want of development in the retinal elements and not to a central cause, as these amblyopic eyes can appreciate and do know large letters. Assuming this condition, associated with the normal power of the lateral moving muscles, as proposed in my last paper, The Power of the Interni, in which I claimed that the power of the interni was four times stronger than the externi, and with the " guiding sensation " almost entirely absent from the amblyopia-then, I repeat, assuming these two conditions, we find one eye begins to turn inward at periods ranging from one week to three or four years after birth. Is this not due to the preponderance of normal power in the mus- cle of adduction ? But to proceed, in time the squinting eye becomes fixed, with the cornea toward the inner can- thus, and when the child is old enough to answer questions we find the vision very materially diminished in the con- vergent eye. As time goes on the child knows and names its letters properly; then the vision is found to be normal-in the fixing eye, but is only about one tenth, or g20%-, in the other eye. Now, if we find the above conditions-the child squint- ing when only one week old-surely there can be no con- vergence with accommodation when the eyes are used, yet for all this one eye turns inward. Must not these condi- tions exist ? Do we not have an amblyopia in the squint- 6 STRABISMUS, OR CROSSED EYES. ing eye, or has there been a suppression of any images when at five years of age we find the vision only T, and waiting five years longer it is still the same ? Can any one claim that there has been a loss of physiological sensibility in the eye to reduce vision from the normal to in the first five years, and yet after that, or in the next five years, there has been no further loss of sensibility, as the vision remains the same ? Or may we go still further and say, If the child never has an operation the squint re- mains until the age of thirty years, and then the conver- gence disappears, the eyes are parallel, and remain so, yet we still find the vision ? Has all the loss of vision taken place in the first five years and remained stationary since ? We have all seen these cases. I have examined many of them, and feel convinced that the perceptive power of the retinal element has been the same since birth, and that there has been no loss of physiological sensibility. Again, if the vision is reduced in the first five years the eye ought to suffer still further loss of visual power, and yet we find exactly the reverse in all our cases. In this class we can surely exclude amblyopia ex anop- sia, and conclude that the child has been born with a retina in which there is loss of power to perceive retinal impres- sions for small objects and convey them to the visual cen- ters. They will not be improved by the use of glasses or by an operation, except in reference to the cosmetic effect. Grantingall this, and associated with it we have the nor- mal power of the straight muscles in adduction and abduc- tion, and taking from the eye its power of fixation or guiding sensation, due to the amblyopia, then in time this eye must turn in the direction of the most powerful muscle-namely, inward-but will again resume its proper position when STRABISMUS, OR CROSSED EYES. 7 forced to fix on an object, by cutting off tbe stimulation to fix in the other eye with a screen, called concomitant squint. This is not a pre-existing disturbance of muscular equi- librium (Fuchs), nor is the squint due to the eyes assuming a position of rest, as advocated by Stilling and Swan Bur- nett, but rather is due to the normal power of adduction over that of abduction when the retina is deprived of its guiding sensation by amblyopia. Hence I do not fully accept the view's of the writers quoted above, as I believe a position of rest is found when the eyes are directed to a point fifteen feet distant and about fifteen degrees below the horizon ; but I assert that the more powerful muscle-the internal rectus-has overcome its antagonist and remains in a condition of tonic contrac- tion, thereby turning the eye inward, or outward, should the preponderance of power be in the external rectus. Since writing the paper I have examined some cases of amblyopia without squint, and have found the externi strongest or equal to the interni. If we continue the history of our cases still further, the eye turning inward, the internal rectus remains contracted until about the twenty-fifth year, when the convergence dis- appears. Why ? Because the power of the interni has now become so reduced from continued contraction that it equals that of the externi, and the eye resumes its proper position. Now the amblyopic eye will follow its fellow eye, but the vision remains the same as in childhood. We may, then, conclude that those cases under our first class are born with an amblyopic eye, and that the normal power of the inter- nal rectus, deprived of the psychical stimulation of the guiding sensation, is the primal and chief cause of the strabismus. These cases can not be corrected by the use of any glasses, but must be operated upon by a complete tenoto- my just as soon as the eyes can be tested in reference to 8 STRABISMUS, OR CROSSED EYES. their visual power. Until an operation has been performed glasses or exclusion of the eye will be simply useless; but after the operation the glasses may be used to relieve any strain on the accommodation. The hyperopia was not a factor in the causation of this class of strabismus. Let me now illustrate our second class of cases. We find a child born with normal eyes, both in reference to vision and the power of the straight muscles, but having a hyperopia of two to four dioptres, with possibly weak ac- commodation. Now, we soon notice that as it begins to play with small toys or use the eyes at the near point, it begins to turn one eye inward at times, called periodic squint. This continues until the child is five or ten years old, when one eye remains constantly turned inward, called fixed squint. Now, on testing, we find a loss of visual power in the retinal elements, or a loss of " physiological sensibility through psychical exclusion." The vision is naturally di- minished in one eye from disuse, the so called amblyopia ex anopsia, simply from suppression of the visual images in the visual centers. But not amblyopic, because the retinal sensibility still exists and will be readily restored by forc- ing the squinting eye to be used by stopping the relative action of accommodation and convergence by atropine and correcting the refractive error by glasses. We have here, under these conditions, what Bonders first called relative hypermetropia; so let us see how we may explain it more fully. We know that the centers for accommodation and con- vergence are very closely associated in the oculo-motor centers, beneath the aqueduct of Sylvius and the floor of the fourth ventricle; and as the child begins to use the eyes to accommodate the vision to a point, say twelve inches dis- tant, it can not overcome or correct its hyperopia. To do STRABISMUS, OR CROSSED EYES. 9 this, therefore, the child requires a greater power of accom- modation. The stimulation for this condition is conveyed to the cerebral centers, so stimulating the power of conver- gence by the association of these centers, and by an excess- ive convergence the child soon learns to see clearly at the distance of twelve inches. In other words, by a conver- gence of the visual lines to a point six inches distant, the child attains sufficient accommodation to see clearly at twelve inches, and the rays of light from the object will form a clear image in the retina of the fixing eye. Its fellow-eye is now found to have its visual line directed to a point much nearer than the object or squints inward. Assuming, and in fact knowing, this to be the condition present, what becomes of the images formed on the retina of the squinting eye ? First, the image of the object falls upon the least sensitive parts of the retina-namely, the inner peripheral part, there forming an indistinct image ; secondly, the image, whatever it may be, that is formed at the macula,, or most sensitive part of the retina, is not in focus, the rays coming from a far different plane than the object, and again we have an indistinct image. Consequently the visual centers will readily suppress these indistinct images formed on the retina, and only sin- gle distinct vision is carried to the visual centers. We may now say there is a loss of vision from " physiological sensibility through psychical exclusion " in the squinting eye, but we must remember that the sensitive retinal ele- ments are still the same and may be rapidly developed to their former standard at birth as soon as the eye is again used under proper conditions. Is this condition amblyopia ex anopsia, or is it only temporary suppression of the visual image ? Test these cases, when first seen, after they have sup- STRABISMUS, OR CROSSED EYES. 10 pressed the image in the squinting eye for several years, and we will find the vision very much reduced-about fl or less. Now use a mydriatic, as atropine, to complete pare- sis of the ciliary muscle, correct the existing error of re- fraction, and in a few weeks we will soon find a return of the previous normal power to see and the vision becomes |f(, or normal. We have corrected the relative hyperopia, the "guiding sensation" reasserts itself, the squint has disappeared. The normal muscle balance remains, and in time, should the accommodative power become stronger by the use of glasses, they may be laid aside without a return of the con- vergence, and an operation has not been necessary to cor- rect the squint. Under these two classes I feel we can place all our cases of strabismus, putting all pathological conditions in the first class, and by them we can explain all and every phe- nomena that is observed. It is well known that persons are born with amblyopic eyes and yet do not squint-both visual lines are properly fixed on the object; they have no asthenopia, no conver- gence, nor does the vision in the amblyopic eye become bet- ter or worse. No; the visual power remains the same through life, yet they do not squint, because in these cases 1 believe we have an insufficiency of the power of the interni (well shown in a case lately examined) and not the normal power of the lateral moving muscles, of four to one, so as to cause the amblyopic eye, with its loss of the guiding sensation, to turn inward in the direction of the powerful muscle acting against its weaker antagonist. In conclusion, if we accept, these views we may decide that in the first class amblyopia is simply and positively the cause of the convergence of the visual axis and not a STRABISMUS, OR CROSSED EYES. 11 consequence of that condition ; the lesion is ocular and not central, nor can it be restored. That in relative hyper- opia we may have a temporary suppression of the visual image, not the so-called amblyopia ex anopsia, and that we may order our treatment of all our cases from a standpoint that will at once be indicated for the correction of this deformity of the position of the eyes. We will not please ourselves with the idea that we have restored useful, perfect vision in an amblyopic eye, but that in the first class we have corrected a cosmetic de- formity by an operation, and in the second class we have restored a dormant physiological sensibility of the retina by the use of atropine and glasses. I will not detain you with a report of my cases, both in clinical and private practice, that I have observed in the past few years, particularly since I have noted the discus- sions of the restoration of vision in amblyopic eyes in the medical journals ; but I wish to state that a careful tudy of all my cases and of those reported, when the his- stories have been at all accurate and complete, have only tended to convince me that the suggestions contained in this paper are correct and will bear the closest investiga- tions. The other evening I was asked by a member of this society when I would operate in a case of strabismus con- vergens ? and I would answer that question simply by stat- ing, first decide to which class the case belongs. If to the first class, then operate at any time-at five years of age is the best-while if to the second class, then you must use the atropine and glasses even at two years of age, as reported by Savage, and you may correct the convergence without an operation in the majority of cases. But this means failing, then you must operate after a fair trial of the glasses for six months. I do not believe we shall ever 12 STRABISMUS, OR CROSSED EYES. have a divergence after a careful operation in the first class, while after an operation in the second class, by so altering the normal balance of power, we may have that un- fortunate occurrence of the operated eye turning the other way- d i vergence. In presenting these views I do not wish it to be under- stood that there may not be other causes for the production of convergent squint, but we may place under the same conditions as I have shown in the first class all cases that present any pathological conditions in the dioptric appa- ratus, the retina or vitreous, for in all these cases we may have the normal balance of the lateral moving muscles and the same loss of the guiding sensation that we know must exist in amblyopia. 163 East Thirty-seventh Street. The New York Medical journal. A WEEKLY REVIEW OF MEDICINE. EDITED BY FRANK P. FOSTER, M.D. THE PHYSICIAN who would keep abreast with the advances in medical science must read a ZtW weekly medical journal, in which scientific facts are presented in a clear manner; one for which the articles are written by men of learning, and by those who are good and accurate observers ; a journal that is stripped of every feature irrelevant to medical science, and gives evidence of being carefully and conscien- tiously edited ; one that bears upon every page the stamp of desire to elevate the standard of the profession of medicine. Such a journal fulfills its mission-that of educator-to the highest degree, for not only does it inform its readers of all that is new in theory and practice, but, by means of its correct editing, instructs them in the very important yet much-neglected art of expressing their thoughts and ideas in a clear and correct manner. Too much stress can not be laid upon this feature, so utterly ignored by the " average " medical periodical. Without making invidious comparisons, it can be truthfully stated that no medical journal in this country occupies the place, in these par- ticulars, that is held by The New York Medical Journal. No other journal is edited with the care that is bestowed on this; none contains articles of such high scientific value, coming as they do from the pens of the brightest and most learned medical men of America. A glance at the list of contributors to any volume, or an examination of any issue of the Journal, will attest the truth of these statements. It is a journal for the masses of the profession, for the country as well as for the city practitioner; it covers the entire range of medicine and surgery. A veiy important feature of the Journal is the number and character of its illustrations, which are unequaled by those of any other journal in the world. They appear in frequent issues, whenever called for by the article which they accompany, and no expense is spared to make them of superior excellence. Subscription price, $5.00 per annum. Volumes begin in January and July. PUBLISHED BY D. APPLETON & CO., 72 Fifth Avenue, New York.