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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    §22. Asthenopia A peculiar morbid condition of the eyes has long attracted the atten- tion of ophthalmologists. The phenomena of which it is composed are highly characteristic. The eye has a perfectly normal appearance, its movements are undisturbed, the convergence of the visual lines presents no difficulty, the power of vision is usually acute,—and nevertheless in reading, writing, and other close work, especially by artificial light, or in a gloomy place, the objects, after a short time, become indistinct and confused, and a feeling of fatigue and tension comes on in, and especial- ly above, the eyes, necessitating a suspension of work. The person so affected now often involuntarily closes his eyes, and rubs his hand over the forehead and eyelids. After some moments' rest, he once more sees distinctly, but the same phenomena are again developed more rapidly than before. The longer the rest has lasted, the longer can he now continue his work. Thus, after the rest of Sunday, he begins the new week with fresh ardour and fresh power, followed, however, by new disappointment. If he is not occupied with looking at near objects, the power of vision appears to be normal, and every unpleasant feeling is entirely absent. If, on the contrary, he endeavours, notwithstanding the inconvenience which arises, by powerful exertion to continue close work, the symptoms progressively increase: the tension above the eyes gives place to actual pain, sometimes even slight redness and a flow of tears ensue, everything is diffused before the eyes, and the patient now no longer sees at first well, even at a distance. After too long- continued tension, he is obliged to refrain for a long time from any close work. It is remarkable that pain in the eyes themselves, even after continued exertion, is of rare occurrence. At first this condition was considered as a sort of amblyopia. It was called hebetudo visus, amblyopie presbytique, or amblyopie par presbytie. By degrees the cause was sought more and more in the organs of accom- modation, at first in the action of the external muscles, subsequently in that of the internal muscular elements; and in the same measure was the importance of the retina thrown into the shade. Excessive tension of accommodation was looked upon as a satisfactory cause of the troublesome symptoms which, it was hoped, might be overcome by rest. Evidently, however, when it was supposed that the origin of asthen- opia was thus explained, the facts were overlooked that thousands in like manner, sometimes in a still higher degree, put their power of vision upon the stretch, without being visited by the troublesome phenomena of asthenopia or impaired vision, and that, on the other hand, these phenomena not unfrequently occur in men, nay, even in children, who had exacted but little from their power of vision. Since the same cause does not produce in every one the same devia- tion, writers are accustomed to take refuge in a peculiar predisposition. But if the foundation of this peculiar predisposition be dark and ob-