Ophthalmic pachymeter and method of making ophthalmic determinations

Abstract

An ophthalmic pachymeter which is highly effective in aiding in the determination of thickness and the optical density of the cornea of an eye on a real-time basis. The pachymeter therefore lends itself to effective employment in aiding in radial keratotomy and other surgical procedures with respect to the eye. The ophthalmic pachymeter of the invention has three major subsystems which include a television camera, a multiple slit projector and an associated processing and display system. In a broad form, the invention comprises illuminating a selected portion of the cornea, moving a slit across the cornea and generating Tyndall image ray paths for enabling analysis of the optical density of the cornea and the thickness of the cornea. This is accomplished through a series of digitally-encoded television images of the optical section of the cornea produced by a multiple slit projector and which images are then subjected to digital analysis. A locus of each of the significant elements of the reflected image of the anterior portion of the eye is defined. In this way, the optical character of the cornea/air interface is compared with the corrected reflectance of the stroma and the endothelium, in order to determine relative transparency. A density map may be constructed in parallel slices for display as a three-dimensional plot of the frontal surface shape of the cornea and for defining and displaying the local thickness, the posterior surface contour, and the optical density of the cornea.