Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Folding
Patent
1977-04-25
1978-09-12
Sacher, Paul A.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Folding
351 34, 351 39, A61B 302
Patent
active
041133633
ABSTRACT:
An apparatus and process for determining subjective astigmatic and spherical prescription for the eye is disclosed. A target, consisting of a line of small angular divergence, is focused for maximum clarity by the adjustment of spherical optics, causing the line to become proximate to the retinal viewing plane of the eye. Change of astigmatic correction is made along at least one axis diagonal to the line target until maximum sharpness of the line results, without resultant spherical change and resultant movement of the image away from the retinal plane of the eye being tested. A second target, again consisting of a line of small angular divergence, is introduced; this line target is angularly inclined to the first target, preferably at 45.degree.. Spherical adjustment is made to obtain subjective line sharpness. Change of astigmatic correction is made along at least one axis diagonal to the line target until maximum sharpness of the line results, without resultant spherical change and resultant movement of the image away from the retinal plane of the eye. By the expedient of vector analysis of the two astigmatic components, astigmatic correction can either be plotted on Cartesian coordinates (in accordance with a technique recently developed), or conversion to the more conventional polar description of astigmatism using cylinder power and rotation can occur.
REFERENCES:
patent: 3785723 (1974-01-01), Guyton
patent: 3841760 (1974-10-01), Guyton
patent: 3947097 (1976-03-01), Humphrey
Humphrey Instruments Inc.
Sacher Paul A.
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