Eyestrain (commonly called asthenopia) / by Ernest Clarke.

  • Ernest Clarke
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Eyestrain (commonly called asthenopia) / by Ernest Clarke. Source: Wellcome Collection.

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    Under atropine, keratoscopy reveals hyperopia in both eyes to the extent of 3 D. a = 8+3 = II D. He has been able to dissociate his accommodation from his converg- ence efforts and thus avoided squint, and his asthenopia is due to the excessive use of accon-imodation over convergence. He was given convex glasses 1.5 D. for both eyes for constant use, which in a short time effectually removed his troubles. Asthenopia from Abuse—Spasm of Accommodation— Slight Hyperopia. F. M., 25, seamstress. Her work is very fine embroider}^ She complains after work of pain in the eyes and brow, and very often lately the pain comes on during work. LV < ^ Under homatropine, the shadow test shows that she is very slightly hyperopic, viz., +.5 D. in both eyes. She was given glasses +1 D. to wear at her work. XI. ASTIGMATISM f A privative, o-rtV/^a a point) as its name implies, is a condition of the eye in which the rays passing through, do not all focus at one point, we have: (1) Irregular Astigmatism : this is due to a difference of refraction in different parts of the same meridian. It is produced by various causes, among them being, a differ- ence in the refractive power of the several sectors of the lens; changes, or displacements of the lens ; and changes in the cornea, such as nebulae. (2) Regular Astigmatism ; this is due to a difference of refraction in different meridians of the eye, the maximum and minimum being at right angles to each other. Parallel rays passing through a convex spherical lens unite at a point, the principle focus, if the curvatures of the lens are all uniform ; but if this is not the case, if for instance, the vertical curvature is greater than the horizontal, the rays passing through the former, will unite sooner than those passing through the latter. This is what we find in regular astigmatism. If the curvature of the horizontal
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