A keratometric photokeratoscopic study of 220 eyes representative of a normal population leads to the ellipsoid corneal model proposed. This model is applicable to the design of rigid corneal lenses and to the calculation of computer models of the dioptric system of the eye. The results obtained show that (1) there is a systematic difference between central keratometric and photokeratoscopic measurements that is statistically but not clinically significant, (2) a significant number of corneas steepen at the periphery, (3) the corneal shape varies greatly with a normal population and (4) peripheral and central astigmatisms are usually similar.