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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    has been expressly pointed out, at the commencement of this chapter, that the deviation always commences as soon as an object has been steadily looked at, and consequently it is totally independent of the state of accom- modation prevailing at the time—convincingly proves that he did not think of hypermetropia, which itself requires a straining of accom- modation while looking at distant objects. From all this, it is evident that hints were not completely wanting in literature, tending, after the slighter degrees of hypermetropia were detected, to connect it with strabismus. III. DIVERGING STRABISMUS. Diverging strabismus depends, as a general rule, on myopia. At the commencement of my statistical researches I was akeady aware of the relations which existed between hypermetropia and converging stra- bismus; but I was very far from supposing that there was at all the same intimate connexion between diverging strabismus and myopia. It was systematic investigations alone that brought this fact first to light. The nature of the relation is not altogether the same in both case?. If hypermetropia determines the converging squint, it is because the anomaly of refraction requires great efforts of accommodation. WTien diverging strabismus arises in connexion with myopia, then the anomaly of refraction as such, is not altogether without direct influence, but the chief cause of the deviation depends on the distension and change of form of the globe of the eye. When myopia exceptionally occurs, owing to a flattening of the cornea, strabismus is not to be looked for. Since Arlt23 demonstrated, by anatomical researches, that ordinary myopia depends on the extension of the membranes of the posterior portion of the globe, and the lengthening thereby of the optic axis, this important fact has been generally admitted as correct. All the diameters of the globe are increased in myopia, but especially that which corresponds to the optic axis; it follows that the globe has a tendency to take the form of an ellip- soid, of which the major axis is the optic axis. These large diameters may diminish the mobility of the eye in general; this is especially caused by the ellipsoidal form, which opposes a much greater resistance to its rotation on its minor axes in the interior of a cavity of the same shape, because this demands a change of form. The centre of motion is not only at a distance from the anterior, but also from the posterior pole of the eye ; its position is not very unfavourable.