An instrument is described which automatically measures the radius of curvature of the cornea and other spherical surfaces. The principle involves moving a light pattern across the face of a cathode-ray tube. After being imaged by a lens and reflected off the cornea, the light strikes two photocells. The placement of the photocells and the lens and the geometry of the cornea determine the positions on the cathode-ray tube face from which light must issue for its reflection off the cornea to reach the photocells. The measurement is in the form of an electronic signal and the accuracy is comparable to that of an optical keratometer.
GERALD WESTHEIMER and LEE FELSENSTEIN, "Automatic Photoelectric Keratometer," J. Opt. Soc. Am. 56, 807-810 (1966)