Ocular refraction and the shadow test . through this meridian. Figure 113 illustrates the correction of the condition depicted infigure 112, the correction being made with a convex spherical lenscombined with a concave cylinder. First, the convex spherical is imposed, this corrects the hyperme-tropia in the vertical meridian, but increases the tnyopia in the hori- I3S R A C T zontal. Next, the concave cylinder is imposed, axis vertical, tocorrect the myopia. In figure 114, I represents the pupil of a compound astigmaticeye. In the vertical meridian the refraction measures + 58. D., inthe horiz
Ocular refraction and the shadow test . through this meridian. Figure 113 illustrates the correction of the condition depicted infigure 112, the correction being made with a convex spherical lenscombined with a concave cylinder. First, the convex spherical is imposed, this corrects the hyperme-tropia in the vertical meridian, but increases the tnyopia in the hori- I3S R A C T zontal. Next, the concave cylinder is imposed, axis vertical, tocorrect the myopia. In figure 114, I represents the pupil of a compound astigmaticeye. In the vertical meridian the refraction measures + 58. D., inthe horizontal meridian, + 62. D. II represents a sphericallens of 2 00 D. Ill represents a concave cylinder of D., theaxis being vertical. The two lenses in the positions designated, com-bined with the refracting system of the eye equals + 60. D. in everymeriilian, or the theoretical emmetropia. To represent astigmatism with the model shown in figure 103,cut one of the tapered points, either I. or II., a bit shorter than Figure The principal meridians of an astigmatic eye; the vertica. nieasurlal. -I- 62. D., illustrated by diagram I The convex spherical of nder of — 4 00 D. axis 90 is shown by III. Lem of tlie eye, equal the arbitrary emmetrmeridian. by II; the concave 1h the retracting ng +58 D . the horizon-+ D is representedThe two lenses, combined)pia of + 60. U. in every In Astigmatism, the wearing of a correction involves both visualacuity and effort of accommodation. The astigmatic person frequently considers that he is near sight-ed, because by holding small objects, notably fine print, closer to theeyes than the customary reading distance, he is enabled to see moredistinctly. By so doing he creates a larger retinal impression and is thus en-abled to see more easily. In the majority of cases of astigmatism, when a convex cylinder isrequired for correction, the axis will be found to be at or near thevertical meridian. If concave cylinders are requ
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