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.

    45/52 (page 33)
    disturbance of the muscles (paralysis, inflammation, contraction, com- plicated congenital anomalies, &c.; a blind eye frequently also deviates outwards), yet myopia does not occupy the same prominent position as a cause of diverging strabismus, as hypermetropia does in relation to converging strabismus; at the same timej however, myopia is found in about two-thirds of the cases of absolute' diverging strabismus. If we add to these cases those of relative diverging strabismus, then the diverging form of squint is quite as frequently met with as the con- verging, if not even more so, and the extraordinary causes, proceeding originally from affections of the muscles, or from blindness of one eye, retire completely into the back ground, for in at least ninety per cent, of the cases of relative diverging strabismus, myopia is found. It has often been remarked, that while converging strabismus is chiefly to be met with in children, diverging strabismus but rarely occurs until much later in life. The observation is correct; the fact is closely connected with the cause of its existence—progressive myopia. Now, although absolute diverging strabismus is, as a rule, chiefly developed out of relative, yet in by no means every instance does the absolute follow the relative ; the reason of this lies in the circumstances we have mentioned; and it seems indeed to be rather the exception. We find here, as in converging strabismus, a similar relation to the cause. Thus as the majority of hypermetropic people remain free from it, so it is also certain that many myopic people will be found with relative diverging strabismus, and yet the absolute form never developed therefrom. Here, then, the question likewise arises—what collateral circumstances operate to produce the true absolutely diverging strabismus ? Perhaps we shall be able to invert the question, if we, in the first place, reflect—why the relative distortion, in general, disposes to the absolute. The result of this examination may be thus formularised. Relative diverging strabismus determines the formation of different images on the two yellow spots of the retinae, at least in the case of close vision. The great desire that these impressions should correspond—the struggle for simple binocular vision, must, in general, be thereby very much weakened. A deviation commencing at the first attempt at convergence, at once becomes considerable, whilst the individual simply yields to the mus- cular impulse; perhaps this occurs, too, in order to remove (however unconsciously), the double images further from each other, or even to exclude the effort of accommodation, which is associated with troublesome F