Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Folding
Patent
1974-03-18
1976-03-30
Sacher, Paul A.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Folding
351 34, 351 39, A61B 302
Patent
active
039470970
ABSTRACT:
An apparatus and process for determining subjective astigmatic and spherical prescription for the eye is disclosed. A target, consisting of a straight line, 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 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 straight line, 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 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. A specialized line target consisting of a three point source smeared by the superimposition of strong cylinder in the range of 4 to 12 diopters is disclosed. This specialized target, when the point sources are arrayed in a triangular configuration, can be adjusted using patient Vernier visual acuity, a visual acuity common to a high degree in large numbers of the population.
REFERENCES:
patent: 3498699 (1970-03-01), Wilkinson
patent: 3841760 (1974-10-01), Guyton
Humphrey Instruments Inc.
Sacher Paul A.
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