On the pathogeny of squint / by Professor Donders ; translated from the German, with a preface, by E. Perceval Wright.

  • Donders, F. C. (Franciscus Cornelis), 1818-1889.
Date:
1864
Catalogue details

Licence: Public Domain Mark

Credit: On the pathogeny of squint / by Professor Donders ; translated from the German, with a preface, by E. Perceval Wright. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    * * Vll more or less deficient, can, by convergence, assist this defective action. But the convergence, in changing the line of vision, brings on, as its consequence, diplopia. And we have a dislike to double images ; there is, therefore, a combat between the desire to see objects sharply, and the necessity—not less imperious—to see single. More often the accommoda- tion is sacrificed—sometimes, however, it is the simple binocular vision. This is what happens, for example, when the eyes are very unequal in quality. In the other case one sacrifices, without hesitation, the less distinct image. When the convergence is fearlessly called to the aid of the defective accommodation, it produces a convergent squint.' It has, unhappily, escaped the notice of my distinguished confrere, that I admit, however, ' two orders of auxiliary conditions, which, in the case of hypermetropia, contribute to produce this affection. The first, I state, is a certain facility—a congenitally too great convergence—a disposition which can be connected with the insufficiency of action of the external rectus. The second is in connexion with external causes.' (Vide Compte-rendu, p. 151.) Now if my memoir had been published in full, in French, before the publication of these Leqons, M. Giraud Teulon could have better convinced himself that I was far from neglecting the primitive tendency of these muscles. He would have found, demonstrated in an exact manner, that this tendency may favour, in general, the development of squint among hypermetropic people, on account of the relatively large divergence of the optic axes, which correspond to the direction parallel to the lines of vision. He would, again, have seen that I collect into two classes the circumstances which favour the development of squint among hypermetropic people, the difference of the eyes, and the tendency of the muscles, either absolute or relative. My excellent friend is, it appears to me, wrong in neglecting the first of these, and attributing all to the second. But he goes still further. That which is for me a circumstance which favours squint, is for him the true cause, principal, or unique. This cause is not, according to his view, hypermetropia itself, and the difficulty of accommodation proportionate to the convergence, but it is the insufficiency of the external recti which so often accompanies hyper- metropia. M. Giraud Teulon cites the following experiment, which, he says, he has often tried:—'Let us place before one of our eyes a concave glass proportion ably strong (-J3) ; the other eye having a convex glas3 of the same number, we thereby render ourselves hypermetropic on the one aide, and not less myopic on the other; now, fixing our looks on