Ocular refraction and the shadow test . eye. Parallel rays of lightrcle passing through the principal The correction of Myopia is a concave spherical lens of such poivei\that couthincd ivith the refracting system of the eye, their principalfocus ivill be upon the The correction of Myopia represented by diagram The parallidivergence, by the imposed concave spherical lens, to enable the Let figure 109 represent a sectional view of a myopic eye, theparallel rays of light are seen to converge at the principal focus, whichis in front of the retina, and then diverge to reach the retina as a
Ocular refraction and the shadow test . eye. Parallel rays of lightrcle passing through the principal The correction of Myopia is a concave spherical lens of such poivei\that couthincd ivith the refracting system of the eye, their principalfocus ivill be upon the The correction of Myopia represented by diagram The parallidivergence, by the imposed concave spherical lens, to enable the Let figure 109 represent a sectional view of a myopic eye, theparallel rays of light are seen to converge at the principal focus, whichis in front of the retina, and then diverge to reach the retina as adiffused circle. This is a typical case of axial myopia, the dotted cir- 134 O C U I. A R REFRACTION. cle, passing through the optic centre of the refracting system and itsprincipal focus, indicates the lengthening of the globe of the eye. Figure i lo is intended to show how the correcting lens affectsthe parallel rays; being a concave lens it causes them to diverge, andas the myopic eye has too short a focus for its length, if the concavelens is correctly adapted, the divergent rays are brought to a focusupon the retina. In figure in, I, represents the pupil of this myopic eye, the mer-idians represented measure + 66. D. II. is its correction, a —
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