Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1980-06-27
1983-12-13
Rosenberger, R. A.
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351247, A61B 310
Patent
active
044202288
ABSTRACT:
An analysis of the corneal shape through the combination of several keratometer measurements is disclosed. The eye is preferably scanned to a nasal angular position, a central angular position and a temporal angular position. The central position is straight ahead along the patient's line of sight. The temporal and nasal positions are in the broad range of up to 5.degree. to 22.degree.; the intermediate range of 10 to 15.degree.; and the narrow range of 12.degree. to 14.degree. on either side. Measurements in sphere, cylinder and axes are taken. Astigmatism is in the more preferable format of 0.degree.-90.degree. astigmatism and 45.degree.-135.degree. astigmatism. When each individual point is measured with its respective estimate for sphere and cylinder components, these measurements are fitted to an idealized parameter. Then the three sets of curvature measurements taken at the specified locations are reduced to a set of adjusted, idealized curvatures all fitted to an elliptical model. Thereafter, these fitted values create final corneal shaped parameters, the particular process here including the creation of intermediate parameters. Finally, readings of central "k", corneal shape, apex position, cap size, vault height, corrected central "k" and goodness of fit are all set forth.
REFERENCES:
patent: 3453437 (1969-07-01), Westheimer et al.
patent: 3781096 (1973-12-01), Townsley
patent: 4019813 (1977-04-01), Cornsweet et al.
patent: 4182572 (1980-01-01), Humphrey
patent: 4199816 (1980-04-01), Humphrey
Humphrey Instruments Inc.
Rosenberger R. A.
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