PMID: 8942133Oct 1, 1996Paper

Superposition of sphero-cylindrical lenses using contour graphs

Journal of the American Optometric Association
R P Hemenger

Abstract

The superposition of thin sphero-cylindrical lenses with arbitrary angles between cylindrical axes is sometimes required in a clinical setting. For example, it may be useful in some instances to perform an overrefraction which, added to the spectacle or toric contact lens in place on the eye, yields a final correcting lens. Computer calculations have been used to create contour graphs allowing a graphical solution to the problem of combining sphero-cylindrical lenses. Although conceptually strightforward, the method has not been presented before. The use of contour graphs to superpose sphero-cylindrical lenses is shown by examples to be accurate and much simpler than calculational methods. Lacking a pre-programmed computer, the method of contour graphs offers a practical method of combining sphero-cylindrical lenses.

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