Anatomy and physiology of the eye, with hints for the preservation of the eyesight (1901)
Herbert, John Frederick, 1860- · Philadelphia, Pa., The author · leaf 41
seen as a point, will appear as aline or an oval. The meridia of the greatest and the leastrefraction are called principal meridians. In speaking ofthe principal meridians of astigmatism, the vertical andhorizontal are usually meant. They may, however, occurin any position, and they are, as a rule,… … E.^ur. 22. A. Convex cylindrical lens used for tiie correction of hypermetropic astigmatism. B. Concave cylindrical lens used for the correction of myopic astigmatism. C. Concavo-convex cylindrical lens used for tiic correction of mixed astigmatism. be reversed, astigmatism is said to be against…
Eye · Lenses
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