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
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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)

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    writer expressly states, that myopia depending upon slight degrees of staphyloma scleroticae, may, particularly in the commencement, be again diminished by restraining the eye from looking at near objects. Respect for Hasner's accuracy cannot prevent me from doubting the correctness of this assertion. I have, under all circumstances, found steady increase of M in young individuals; its diminution I have never observed. The task of the oculist in myopia resolves itself into the following: 1. To prevent the further development of the myopia, and the occurrence of secondary disturbances. 2. By means of suitable glasses to render the use of the myopic eye easier and safer. 3. To remove the asthenopia muscularis by the use of glasses or by tenotomy. 4. To combat the secondary disturbances of the M. I. In the exposition already given lies, I think, the proof, that where predisposition exists, continued accommodation for near objects pro- motes the development of staphyloma posticum.. . . We have remarked that accommodation, as such, is not in this case in operation, for in it only the form of the crystalline lens is changed, and in M the latter has undergone no change. In a mediate way, therefore, through accessory circumstances, it must be, that accommodation for near objects promotes staphyloma posticum. Of such circumstances two especially come under observation: strong convergence and a stooping position. As to the first, in order to see acutely, myopes must bring the object within the region of accommodation, and where Mis somewhat advanced, binocular vision under these circumstances requires a strong convergence. Children and young myopes are even accustomed, particularly in bad light, to bring the objects much nearer to the eyes than the degree of the myopia, properly speaking, requires. This strong convergence increases the tension of the eyeball by pressure of the muscles, perhaps also by pressure against the surrounding tissues, and increased pressure promotes the staphylomatous distention. . . . Now strong convergence may be avoided in various ways. In the first place we cause the patient to look much at a distance. But we cannot absolutely forbid looking at near objects, and we therefore give spec- tacles which bring the farthest point, r, to a sufficient distance; for example, to from 16 to 18 inches. At the same time the patient is to be strongly recommended not to look at a shorter distance than 16 or 14, . . . a ruler of this length may serve as a measure to parents and masters as well as to the myope himself. Moreover, it is desirable that often (for example, every halfhour) work should be discontinued for a couple of minutes.—In very high degrees of M, only one eye is usually employed in vision, and thus convergence is excluded. This appears to