Videokeratoscope for accurate and detailed measurement of the cornea surface

A videokeratoscope based on the imaging of a gridlike pattern is introduced. Unlike conventional videokeratoscopes that rely on Placido disks, the new measurement principle allows an exact reconstruction of the surface and the display of fine details. The experimental instrument was tested on precision glass spheres; the maximum error of the height data was less than 3 (mu)m. The sensitivity and the potential to resolve fine details were demonstrated with irregular surfaces of specially prepared contact lenses. Structures with height deviations of 0.1 (mu)m are well identifiable. The eyes of 18 individuals were investigated, and fine structures were found on these cornea surfaces. Conventional videokeratoscopes do not resolve such detail.