Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1992-11-06
1994-07-26
Ben, Loha
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
359708, 359712, A61B 310, G02B 302
Patent
active
053330170
ABSTRACT:
The lens of the invention is specifically designed for use with a slit lamp biomicroscope in the examination of a patient's eye. One or more lens elements may be used with each lens element having first and second convex aspheric surfaces of revolution. The first and second aspheric surfaces are coaxial and non-symmetrical with respect to one another. The aspheric surfaces 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 radius 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 biomicroscope.
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R. David Sudarsky, M.D. et al, "Aspherical Objective Lenses", (1959), pp. 572-575, American Journal of Ophthalmology, vol. 47, No. 4.
Ben Loha
Robbins Thomas
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