Abstract: An improved photokeratoscopic method and apparatus for measuring corneal curvature and topography. The principal of parallax is used by generating a reference light point outside of the relevant plane of a ring generator, such that the relative apparent position of the reference light point with respect to the projected light rings provides a calibration reference that varies with distance of a cornea from the photokeratoscope. More particularly, the invention determines the coordinates in space and the tangent angle of the reflection point on the corneal surface of the image of the reference light point. This information defines the actual corneal topography at the reflection point, without making assumptions. These coordinates and tangent angle can be used to determine the actual distance d from the photokeratoscope lens to the apex of the cornea. An exact value of d permits better accuracy in calculating the central corneal radius of curvature and corneal topography.

Abstract: A method and apparatus for smoothing and homogenising the cross-sectional intensity distribution of the output from an excimer laser for improved application of excimer lasers to optical laser surgery to the cornea. The laser beam is focused by means of a cylindrical lens or mirror and then filtered using a narrow gap spatial filter to smooth the intensity distribution by removing high spatial frequencies. The resulting output beam may be collimated by means of a second cylindrical lens or mirror for application to further optical processes.