. Refraction and muscular imbalance, as simplified through the use of the ski-optometer. 3-A — Outer spherical reel containing Cx. sphericals from .025 to and a 3-B — Inner spherical disk containing Cx. sphericals, automatically turns within 3-A.

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Keywords: ., bookcentury1900, bookdecade1920, bookidrefractionmu, bookyear1921