On the etiology and treatment of convergent squint.

  • Snell, Simeon, 1851-1909.
Date:
[1887]
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Licence: Public Domain Mark

Credit: On the etiology and treatment of convergent squint. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    standpoints. Authoiity in medicine is held in no greater awe than it is in general science or politics. This is a matter for congratulation, and it may well be considered a healthy sign, for to whichever side our opinions may lean, it is much to be desired, that the subject should now be thoroughly discussed and something like truth arrived at. Some of the criticisms against the usually accepted amblyopic theory have been urged agiinst it, as if it rested entirely on simple exclusion from use. Thus, for instance, the fact that cataract may exist for many years, and then be removed with successful restoration of vision has been trotted out to do duty against such a theory. There is a manifest difference between the case of a child just commencing to observe closely and such a case as the suggested cataract. There is, moreover, no question of any mental process. It can hardly be denied that suppression of sense impression does take place. As soon as our attention is entirely engrossed upon anything we are in a position to disregard the impressions upon all other organs of sense ; they do not reach our consciousness. It is contended that the mind in strabismus is intent on the image from the fixing eye, and disregards the imperfect one formed excentrically in the other organ. Schweigger may be put forward as the most redoubtable opponent of Bonders' theory. He regards the amblyopia as identical with a congenital form which in one of its forms is always monocular. He has supported his opinions with elaborate statistics. All of us are accustomed to observe cases of congenital amblyopia, but I doubt if we are prepared to accept his conclusions as to its frequency. It is not easy to calculate the percentage of squints in hypermetropes ; it can only be done by estimating the proportion of squints to hypermetropes who seek advice. Stellwag has given some- what more than 16 as the percentage of strabismus to cases of hyper- metropia. In 756 cases of hypermetropia, including astigmatism (mixed and hyp.) in my private case-book, as many as 93 possessed manifest convergent squint, the percentage becomes thus a fraction over 14 per cent. Accepting my lower estimate, and taking also Mr. Frost's of 60 per cent, of amblyopia as occurring in strabismus, brings a total of 8.4 per cent, of amblyopia in all cases of hypermetropia. For my part I think I should hesitate to accept such a percentage as this even of cases of congenital amblyopia existing in hypermetropes. Schweigger1 says he sees no difference whether squint is present or not, as the form of defective vision is the same, and nothing happens in the combination with squint which could not also be proved with- out it. Thus I gather that he places congenital amblyopia as having a high percentage in hypermetropia. In 177 cases of hypermetropia, of 1 to 3D, including a few cases of divergent squint, he found defective sight less than } in 31.6 per cent; in hyptrmetropia of 3D and more, in 70 cases of convergent squint the percentage of de- fective sight was 44.2. He remarks, also, that there appears a regular increase of defective sight with the increase of the hypermetropia. This large proportion of monocular amblyopia in hypermetropia I confess my experience hardly prepares me for, and I fancv, full as Schweigger's statistics are, further evidence is necessary before it is laid down as correct that about one-third of the cases of hyperme- tropia are amblyopic in one eye. Donders held that the vision in the deviating eye suffered more and more, aud was of opinion also that vision recovered after tenoto- my, and with practice of the amblyopic eye. Both these circumstances are not in harmony with the facts concerning congenital affections. I shall refer again, to these points. 1 Schweigger, On Squint (English Translation).