GB680044A - Improvements in ophthalmic lenses - Google Patents

Abstract

680,044. Spectacle lenses. AMERICAN OPTICAL CO. June 26, 1950, No. 15930/50. Class 97 (i). A multifocal lens for an eye from which the crystalline lens has been removed comprises a transparent meniscus having a circular shaped seat in its convex surface and a continuous curve on its concave surface, circular in at least one meridian, an outwardly-projecting button being fused to said seat with its periphery coincident with that of the recess, the button comprising at least two adjacent pieces of transparent material having different indices of refraction, one of which is substantially the same as that of the carrier and the outer portion of the button being spherical convex to provide the necessary optical correction, the carrier portion having substantially no power. As shown in Fig. 10, the carrier 13 which may be of crown glass, to which cerium oxide has been added to absorb ultra-violet light, has a circular recess 16 in its convex surface 2 in which is fused a button comprising a portion 12 of glass having the same refractive index as the carrier 13 and a portion 14 of " Barium " Crown Glass of different refractive index. The outer surface of the button is then ground spherical to the curve 1, Fig. 11. A series of lens blanks having different curvatures on the surface of the button may be provided, the rear surface 3 being subsequently shaped to the spherical, toric or prismatic surface desired. A ring tone may be used to grind the surfaces 1 and 2.