. Refraction and how to refract : including sections on optics, retinoscopy, the fitting of spectacles and eye-glasses, ¥lG. 135.—Companion picture to figure 84. Illustrating the indirect from the lamp (L) are reflected convergently from the mirror of theophthalmoscope, and, passing through the convex lens and into the eye,produce a large retinal illumination, extending from I to I. TB are raysfrom the edge of the disc, and, leaving the eye parallel, pass through theconvex lens and form an inverted aerial image of the disc at T B. The4-4 S. in the ophthalmoscope magnifies the
. Refraction and how to refract : including sections on optics, retinoscopy, the fitting of spectacles and eye-glasses, ¥lG. 135.—Companion picture to figure 84. Illustrating the indirect from the lamp (L) are reflected convergently from the mirror of theophthalmoscope, and, passing through the convex lens and into the eye,produce a large retinal illumination, extending from I to I. TB are raysfrom the edge of the disc, and, leaving the eye parallel, pass through theconvex lens and form an inverted aerial image of the disc at T B. The4-4 S. in the ophthalmoscope magnifies the image T B. 15. The cylinder lens test for astigmatism is describedunder Applied Refraction, page 240. 16. Retinoscopy is described in chapter vi. CHAPTER , or the Shadow Test.—This may be de-. Fu;. 136.—TIk; Authors Schematic Eye for Stu<lyinp; Ki-tiiK)scoi)y. fined as tiio method of estimatini; the refraction of an e)-cby reflecting into it rays of lii^ht Axiin a plane or concave 154 RETINOSCOPV. 155 mirror, and observing the movement which the retinalillumination makes by rotating the mirror. Suggestion.—Before attempting to practise retinoscopyupon the human eye, the beginner is advised to study themethod upon one of the many schematic eyes to be foundin the market. The principle of retinoscopy is the finding of the pointof reversal, or myopic far point; and when an eye is emme-tropic or hyperopic, it must be given a myopic far point bymeans of a convex sphere. (Fig. I37-) I METER.
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