Case 38.—Bertha W—, æt. 18, reads with the naked eye on the right No. 0·75 at 10 cm., on the left only 1·75 at the same distance; hypermetropia of 6 D. is detected with the ophthalmoscope, with + 5·5 the visual acuteness of the right eye amounts at 1 metre to 1/9 (if the test-letters had contained No. 8 or 7·5, that would probably have been recognised also), on the left with + 5·5 D., V. = 1/12, with + 6 D. No. 0·8 is read with difficulty. Patient admits to have squinted as a child; no squint is present now; binocular fusion can be detected with prisms and she only squints now and then on the left side to assist vision, with which, patient states without being questioned, diplopia is combined. Spectacles have not been used till now.
I could cite several more such cases, but they would prove no more than these. At any rate the fact is settled that squint can disappear spontaneously, and without the aid of convex glasses even in high degrees of hypermetropia.
Wecker's announcement that "this spontaneous cure goes hand in hand with the progressive decrease of the accommodation, and depends on the fact that the squinter, on the strength of this progressive decrease, renounces more and more the aid which he finds in the increased convergence during the act of accommodation," only proves to how great an extent one may be prejudiced by theories. A limitation of the accommodation must necessarily increase the claims which are made on it, and can only afford inducement for calling forth all the help possible to support the accommodation.
The fact that squint spontaneously disappears after normal binocular fusion is completely and permanently lost, and in individuals who accommodate without the occurrence of a too strong convergence, notwithstanding their hypermetropia and without the help of the controlling influence of binocular single vision, seems to me quite irreconcilable with Donders' theory. Every motive for the same, hypermetropia, difference of refraction, monocular defective vision, &c., may not only be present without the occurrence of squint, they do not even prevent the spontaneous recurrence of a squint already cured. Of course I will not affirm that the causes made so prominent by Donders exercise no influence on the origin of squint, but will only emphasize the fact, that other causes exist which possess a greater influence, and which we can find only in the ocular muscles.
We have no experience as to whether this spontaneous cure occurs in myopia with divergent squint. This is not to be wondered at, as hypermetropia is present in the great majority of cases of squint, and the observations as to spontaneous cure are also rare in these. But I can vouch for one case where a slight absolute divergent squint, with crossed diplopia, which I treated shortly after its origin in a youthful myope, with prismatic spectacles, soon disappeared, and remained permanently cured.
The inclination to preponderance of the interni appears to be peculiar to youth, while later on circumstances change in favour of the externi, and that seems to me the chief ground for the spontaneous cure of convergent squint. The cure is not always complete; deviation still occurs on exclusion, or on particularly keen fixation; sometimes, however, also under conditions which can only be put down to a change in the elastic tensions of the muscles. The following is an interesting illustration of this:
Case 39.—Miss S—, æt. 20, states that she squinted frequently as a child from her fifth to her tenth year; the squint gradually disappeared, but returned again from time to time during the last half year without apparent cause. The examination showed normal position of the eyes, slight convergence only on exclusion. Visual acuteness on the right 5/6, with atropine ophthalmoscopic and functional emmetropia, the visual acuteness is lowered to 5/12 by convex 1 D.; on the left hypermetropia 7 D., visual acuteness 5/18; the same degree of hypermetropia is found with the ophthalmoscope.
Crossed diplopia with a difference in height is distinguished with the aid of a red glass, the difference being corrected by a prism of 4°, with the base downwards before the right eye; a prism of 4° with the base inwards suffices to place the double images immediately above one another. Spontaneous diplopia does not take place; only the right visual field is seen in the stereoscope. As patient lived in Brandenburg and only came to consult me occasionally I never had an opportunity of seeing the squint till she decided to stay here for some time. It was then seen that a peculiar oscillating deviation of the left eye of about 4 mm. inwards often occurred. As the previous spontaneous disappearance of the squint and the crossed diplopia made one fear that tenotomy of the internus might be followed by divergence, instillations were used in order to make a more exact measurement of the deviation,—by this means the condition was so improved in the course of a few weeks, that deviation no longer occurred even on exclusion of the right eye.
The spontaneous cure of squint may, however, be quite complete; indeed I have seen one case where convergent squint became divergent.
Case 40.—A young lady, slightly over twenty years of age, showed on the right M. ·75 D., V = 10/10, on the left H. 1·5 D., V. 10/40 to 10/30, and slight divergent squint on the left side. Crossed diplopia could be produced with a red glass, tenotomy of the left abducens sufficed to correct it. I had not concealed my doubts as to her statement that she had previously squinted inwards, but they were quite dispelled by a photograph taken about twelve years before, in which decided right convergent squint could not be mistaken. There is something to be said for the fact that it may have been a periodic squint, which occurred during the taking of the picture, as the photographer would have taken pains to hide a permanent squint in some way.