Practical Ophthalmic Lenses |
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angle Answer aperture Apparatus appearance astigmatic axis direction base curve bifocal block calculated component convex correct cross crossline chart curvature cylinder axis DC X decentration deduct determine deviation diameter difference dioptres distance Draw edge element equation Error example experiment expressed F₁ Figure filters final focal length focal power focimeter follows front surface given gives glass Hence horizontal incident lens measure lenses lies light limited marks maximum means meridian method metres mirror moved movement negative neutralizing neutralizing set Note object observation obtain optical centre parallel placed plane position prescription prism prismatic effect Procedure produce protractor radius reading Record reflected refractive index Repeat represents rotation scale seen segment shown shows side spectacle sphere spherical standard surface power Theory thickness thin tinted toric unknown vertical