Licence: Public Domain Mark
Credit: Eyestrain (commonly called asthenopia) / by Ernest Clarke. Source: Wellcome Collection.
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Licence: Public Domain Mark
Credit: Eyestrain (commonly called asthenopia) / by Ernest Clarke. Source: Wellcome Collection.
![muscularis/ and a little later in his memorable paper on the subject, says :— Eine andere Quelle der asthenopie ist ganz unabhangig von der accomodationsarbeit und liegt in dem Spannungsverhaltnissen der inneren Augen- muskeln.^ This period marks the final epoch in the history of asthenopia, for these two pioneers, Bonders and Graefe, steered ophthalmologists into the proper channels of inquiry and investigation, and although naturally our knowledge of the subject has increased during the last thirty years, it has not materially altered. Definition.—Asthenopia (A, privative, a-6evo<;, strength, oi-v/r, eye) or eyestrain, is a symptom or group of symptoms, the result of straining some part of the eye apparatus. It has been defined as weak sight. This is wrong, as weakness is no more a necessary feature than it is in any other form of fatigue. Tired sight it may be called, but not weak sight. The word asthenopia is the cause of this faulty definition ; but we cannot afford to discard it, for although the word eyestrain in many respects is preferable—carrying with it as it does its own definition, and implying no theory—it does not supply us with an adjective, and the word asthenopie is very useful. The Varieties of Eyestrain.—Eyestrain arises from strain of three distinct parts of the eye apparatus : — (i.) Ciliary strain, commonly called accommodative as- thenopia, due to strain of the ciliary muscle. (ii.) Muscular asthenopia, due to strain of the extrinsic muscles of the eye; strain of the internal recti, or convergence strain, being the commonest form. 1 Graefe's Arch./. Oph., bd. ii., i, p. i74- ^]bid., bd. viii., 2., p. 321.](https://iiif.wellcomecollection.org/image/b20395747_0018.jp2/full/800%2C/0/default.jpg)
