Applies to instruments, systems and methods that are intended to measure the shape of the cornea of the human eye over a majority of its anterior surface. Instruments classified as Opthalmometers or keratometers are not covered by this standard. This standard defines certain terms that are peculiar to the characterization of the corneal shape so that they may be standardized throughout the field of vision care and have common meaning for all those who have occasion to participate in this area.