Abstract: In an inventive method for mapping the topography of an eye, elevation measurements of the eye are collected using a slit beam diffuse reflection system, such as an ORBSCAN.TM. device. An approximating b-spline surface is then fitted to the elevation measurements. Slope measurements of the eye are collected using a Placido-based reflective system, but the slope measurements are referenced to points on the b-spline surface, rather than to points approximated using the conventional constant curvature method, so the measurements have substantially improved accuracy. The elevation and slope measurements are then blended using weighted least squares fitting techniques. A new b-spline surface is fitted to the blended measurements, with the new surface having substantially improved accuracy in depicting the actual topography of the eye as a result of the elevation-improved accuracy of the slope measurements.

Abstract: In an inventive method for mapping the topography of an eye, elevation measurements of the eye are collected using a slit beam diffuse reflection system, such as an ORBSCAN.TM. device. An approximating b-spline surface is then fitted to the elevation measurements. Slope measurements of the eye are collected using a Placido-based reflective system, but the slope measurements are referenced to points on the b-spline surface, rather than to points approximated using the conventional constant curvature method, so the measurements have substantially improved accuracy. The elevation and slope measurements are then blended using weighted least squares fitting techniques. A new b-spline surface is fitted to the blended measurements, with the new surface having substantially improved accuracy in depicting the actual topography of the eye as a result of the elevation-improved accuracy of the slope measurements.

Abstract: An apparatus for analyzing a subject's cornea includes a frame having first and second ends, a single curvature (i.e. non-planar and non-axisymmetrical) screen associated with the first end of the frame, the non-planar and non-axisymmetrical screen having an opaque covering which is interrupted along its surface to form a pattern. A light source is disposed to cast the pattern placed on the screen onto the subject's cornea, thus causing a pattern to reflect therefrom. A light detector (e.g. a camera, CCD, or human eye) is disposed to sense the pattern reflected from the subject's cornea. The improved Placido plate is easier to manufacture. The design allows for incorporation of extremely complex pattern shapes, while its shape helps to maintain focus of the image.

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.

Abstract: An ophthalmic instrument, in the nature of a pachymeter or densitometer, and which is used for ascertaining the thickness and relative optical density of the cornea of the eye on a real time basis. The instrument comprises a television camera and a multiple Scheimpflug corrected slit projector and an associated processing and display system. A number of digitally encoded television images of the optical section of the cornea are subjected to digital analysis. A density map may be constructed from the data derived in the digital analysis and produced for display either by a printer or display member. The display may be a three-dimensional plot of the frontal surface shape, local thickness, posterior surface contour and optical density of the cornea. A method of using the ophthalmic instrument and of making ophthalmic determinations is also disclosed.