Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1995-03-10
1998-01-06
Nelms, David C.
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351212, A61B 300
Patent
active
057060738
ABSTRACT:
The lens of the invention is specifically designed for use with a slit lamp biomicroscope or operating microscope in the examination or treatment of a patient's eye. The invention consists of one or more coaxial lens elements, with at least one of the lens elements utilizing at least one convex aspheric surface of revolution. The aspheric surface or surfaces utilized are chosen to correct astigmatic imagery of the lens, with the formed aerial image free of excessive field curvature and astigmatism. The lens is held at a distance from the patient's eye pupil corresponding to the secondary focal length of the lens. If the examined eye is emmetropic, and the lens is held in a position wherein the entrance pupil of the lens is conjugate with that of the examined eye, an image of the entrance pupil of the patient's eye will be formed at the pupil aperture of the optical system of the slit lamp biomicroscope used to observe the aerial image of the fundus as produced by the lens. The ratio of the apical radii of curvature of each surface and the ratio of the apical eccentricities of each surface are chosen to optimally correct for astigmatic imagery as well as pupil imagery of the lens, being dependent upon the index of refraction of the optical quality glass or plastic used in the production of such lenses. The indirect ophthalmoscopy lens of the invention therefore provides a sharper, focused fundus image and extremely wide field of view by optimally correcting for the primary image quality of the lens, as determined by astigmatism and image flatness, as well as the spherical aberration of the conjugate pupil image, specific to the pupil of the objective lens system of the observing slit lamp or other biomicroscope.
REFERENCES:
patent: 3944341 (1976-03-01), Pomerantzeff
patent: 4704018 (1987-11-01), Takhashi
patent: 5046836 (1991-09-01), Volk
patent: 5189450 (1993-02-01), Crossman et al.
patent: 5309187 (1994-05-01), Crossman et al.
Nelms David C.
Robbins Thomas
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