The commoner diseases of the eye : how to detect and how to treat them . sand in the eyes, with burning and smartingof the lids and eyeballs and an increased secre-tion of tears. Where the strain is kept up for some timestyes and other affections of the lids are fre-quently met with. When this strain is not re-lieved by appropriate treatment the effort evento see distant objects distinctly also causesmarked discomfort until eventually the patient THE NORMAL AND ABNORMAL EYE 65 is no longer able to use his eyes for any pur-pose, even for a few moments, with condition is known as Ac
The commoner diseases of the eye : how to detect and how to treat them . sand in the eyes, with burning and smartingof the lids and eyeballs and an increased secre-tion of tears. Where the strain is kept up for some timestyes and other affections of the lids are fre-quently met with. When this strain is not re-lieved by appropriate treatment the effort evento see distant objects distinctly also causesmarked discomfort until eventually the patient THE NORMAL AND ABNORMAL EYE 65 is no longer able to use his eyes for any pur-pose, even for a few moments, with condition is known as Accommodative As-thenopia. A farsighted eye, as has just been noted,is a small eye and this abnormal state is due inthe majority of instances to shortening of theantero-posterior diameter of the eyeball, to whichis given the name Axial Hypermetropia. Lessfrequently it depends upon some deficiency inthe curvature of the cornea or lens (CurvatureHypermetropia) or upon the absence of the lens(Aphakia). It is almost invariably a congen-ital and rarely an acquired HYPERMETROPIC EYE CORRECTED BY A CONVEX LENS Parallel Rays AA, made more convergent andFocus on the Retina at P. For the correction of farsightedness it isnecessary that parallel rays of light should bebrought to a focus on the retina without theaid of the accommodation. This is accomplishedby means of a convex lens in front of the eye,of sufficient strength to make the rays, as they 86 COMMONER DISEASES OF THE EYE enter the eye, more convergent. The greaterthe amount of hypermetropia the stronger theconvex lens must be. When there is a spasm of the ciliary muscle(and this condition is more or less present ina large percentage of the cases) a variable amountof the error is masked and in some cases thecramp of the muscle is so great that the eyepresents a condition of false myopia, due to theeffort of accommodation being so great (in theendeavor to focus the rays on the retina) that itis overdone and the rays appa
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