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Article
April 1951

A REVERSIBLE BIFOCAL LENS

AMA Arch Ophthalmol. 1951;45(4):468-469. doi:10.1001/archopht.1951.01700010478013

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Abstract

A METHOD for inverting a bifocal lens is described. A standard Bausch & Lomb "Bal-Grip" mounting is utilized. The lens itself is shaped like a symmetrically "rounded square." This pattern is available in "two difference," "four difference" and "six difference" optical sizes. The lower portion of the lens is notched so that the lens can be inverted when desired. Any type of bifocal or trifocal can be used. The accompanying illustration clearly shows the reversible bifocal. It consists of the regular "Bal-Grip" mounting with a bridge size of 22 mm., a temple length of 6.5 inches (16.5 cm.) and lens size of 46 by 42 mm. The illustrated bifocal is Tillyer B. The lens is shown in both positions.

TECHNIC OF FITTING THE LENS  The bridge size is selected and fitted. The near interpupillary distance is then measured. An eye size is arbitrarily selected so that the horizontal dimension of

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