On the anomalies on accommodation and refraction of the eye : with a preliminary essay on physiological dioptrics / by F. C. Donders ; translated from the author's manuscript by William Daniel Moore.

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

Licence: Public Domain Mark

Credit: On the anomalies on accommodation and refraction of the eye : with a preliminary essay on physiological dioptrics / by F. C. Donders ; translated from the author's manuscript by William Daniel Moore. Source: Wellcome Collection.

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

    258/304 (page 240)
    found this in high degrees both of myopia and of hypermetropia. That the power of vision of a strongly hypermetropic eye . . . has been overlooked, cannot surprise us; but it is singular that clever and well- informed men have so often continued ignorant that they still see satisfactorily with their strongly myopic eye, when they only bring the object near enough. In these cases the unused eye has often deviated somewhat, and indeed almost without exception in the outward direction. This direction I have even met with, when the deviated eye was strongly hypermetropic, provided that myopia, or at least emme- tropia, existed in the other used eye. In general, I must observe that deviation is never produced by difference in refraction. At most the latter may be the cause, why the deviation was not prevented, and it is, in fact, no longer prevented, so soon as the difference in refraction is so great that the one eye loses all importance for binocular vision: this eye is then equivalent to a blind eye, and just like the latter, there- fore deviates outwards. But if the eye has still any co-operation in binocular vision, vision is improved by it, and certainly the deviation never arises in order to prevent binocular vision, as has been asserted. 2. The eyes are alternately used. In difference in refraction it not unfrequently occurs, that the one eye is employed for near, and the other for distant, vision. . . . Now, in these cases, it may appear as if the range of accommodation is extraordinarily great. Thus one of my friends boasted, that at a distance he saw with perfect acuteness, and that in vision for near objects he was inferior to none. On examination this was at once explained. His right eye was emmetropic, and his left presented myopia= 1/5-5. He was himself not aware of this. After his twenty-eighth year this last eye began to deviate outwards, and was thus excluded from binocular vision; but the continues to use it, when he wishes to distinguish very small objects. Thus a deviated myopic eye is most certainly preserved from amblyopia, while, on the contrary, that which has deviated inwards becomes amblyopic throughout the greater part of its field of vision. That it is of importance, if possible, to preserve it from amblyopia, need scarcely be observed. 3. One eye may, in observation, continue wholly excluded. Under this head two kinds of cases are to be distinguished: those in which a morbid condition of the eye {e.g., detachment of the retina) has set in, and has given rise to the exclusion with deviation, and those where the devia- tion was primary, and the disturbance of vision is the result of want of use. With respect to the first we may be silent. As to the last, we must distinguish between the deviation inwards and that outwards. In the deviation outwards the field of vision is enlarged, and extends over objects, which are not seen by the other eye. In the deviation inwards the field of vision is diminished, and that of the deviated eye falls more over the other. This may produce confusion, and therefore we mentally neglect the impressions received on the corresponding part of the deviated eye, which consequently, so far as the common binocu-