. Refraction and muscular imbalance, as simplified through the use of the ski-optometer. Fig. 2—To Obtain Piano. 1—Set spherical indicator at 000 as illustrated above. 2—Set cylinder indicator to 0. 3—Set pointer of supplementary disk at open. The instrument should then be set at zero orpiano, a position indicated by the appear- [1] Refraction and Muscular Imbalance ance of the three ^o o o at the sphericalregister, in conjunction with one ^o, or zero,for the cylinder at its register, marked ^CCCyl. After this move, the supplementary diskspointer should be set at open (Fig. 2).. sphereIndu /it

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. Refraction and muscular imbalance, as simplified through the use of the ski-optometer. Fig. 2—To Obtain Piano. 1—Set spherical indicator at 000 as illustrated above. 2—Set cylinder indicator to 0. 3—Set pointer of supplementary disk at open. The instrument should then be set at zero orpiano, a position indicated by the appear- [1] Refraction and Muscular Imbalance ance of the three ^o o o at the sphericalregister, in conjunction with one ^o, or zero,for the cylinder at its register, marked ^CCCyl. After this move, the supplementary diskspointer should be set at open (Fig. 2).. sphereIndu /itor Fig. 3—To obtain sphericals, turn this Single Reel as shown by dotted finger. This assures an automatic and simultaneous registration at sphere indicator of focus of lens appearing at sight opening. Convex Spherical Lenses A careful study will show that the Ski-optomoters spherical lenses are obtained bymerely turning the smaller reel (Fig. 3).The first outward turn of this reel, toward thetemporal side of the instrument, draws intoposition in rcguhir order the spherical lenses [2] Refraction and Muscular Imbalance , +.50, +.75, and +, as shown inFig. 3a.

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Keywords: ., bookcentury1900, bookdecade1920, bookidrefractionmu, bookyear1921