Process and apparatus for astigmatic and spherical subjective testing of the eye
US4113363A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 25, 1977 |
| Grant date | Sep 12, 1978 |
| Priority date | — |
| Expiry date | Apr 25, 1997 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA61B3/036
- WIPO fieldMedical technology
- WIPO sectorInstruments
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 …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.