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Prismatic effect in bifocal lenses and the location of the near optical centre. 1994

W F Harris
Department of Optometry, Rand Afrikaans University, Auckland Park, South Africa.

A matrix expression is derived for the prismatic effect in the reading portion of a bifocal lens. Using this expression the problem of finding the location of the optical centre of the reading portion is examined. Matrix methods lead to a complete solution that holds in all circumstances within the usual limitations of first-order optics and thin lenses. Both the main and segment lenses may be astigmatic. In the usual case there is a unique near optical centre but situations can occur in which there is no near optical centre or an infinite number of them. These situations are examined systematically. Numerical examples illustrate the method.

UI MeSH Term Description Entries
D008433 Mathematics The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Mathematic
D011932 Reading Acquiring information from text.
D005139 Eyeglasses A pair of ophthalmic lenses in a frame or mounting which is supported by the nose and ears. The purpose is to aid or improve vision. It does not include goggles or nonprescription sun glasses for which EYE PROTECTIVE DEVICES is available. Glasses,Spectacles,Sun Glasses, Prescription,Glasses, Prescription Sun,Prescription Sun Glasses
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D055095 Optics and Photonics A specialized field of physics and engineering involved in studying the behavior and properties of light and the technology of analyzing, generating, transmitting, and manipulating ELECTROMAGNETIC RADIATION in the visible, infrared, and ultraviolet range. Photonics,Photonics and Optics

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