Keratometer having peripheral light entrance and exit paths

Abstract

A keratometer is disclosed in which at least some of the light entrance and exit paths have both peripheral entrance and exit paths. Eye positional information and sphere, cylinder and axis information for each sampled area (preferably in the order of 3) are obtained by analysis of the reflected and returned light. Sample of a multiplicity of areas on the eye occurs simultaneously without eye panning and generates a topographical measurement of the eye useful for contact lens fitting eliminating most of the incidence of refit on patients in placement of prescribed contact lenses. In one embodiment, a moving boundary locus sweeps an area of light emission from a plurality of coded, spaced apart point light sources. The area of light swept is imaged from the source to the cornea. The locus in its occulting sweep is incident upon the eye at a conjugate point image and reflected from the eye in a diverging light bundle to a plurality of detectors each with its own aperture for sampling the image of that part of the moving boundary locus which is deflected by the particular eye curvature and spacing to the detector aperture. In another embodiment, multiple apertures each image a plurality of coded and spaced apart light sources. These light sources are imaged from their source to the cornea. The light sources in reflection from the cornea are imaged to a vidicon tube in a pattern of reflection where image size and spacing yields telltale information relating to eye curvature and spacing. In both embodiments, identifiable light source patterns resulting from triangulation give eye positional information. Likewise in both embodiments, identifiable two dimensional image shapes and size give sphere, cylinder and axis information. Provision is made for light source coding by either modulation or shape.