The Mean Shape of the Human Cornea

Abstract

The anterior surface of the cornea is the major refracting element of the human eye. Knowledge of its shape and the variation of this shape throughout the population are important in calculations of the corneal contribution to ocular aberrations. Since the cornea is the surface on which a contact lens rests, the corneal shape is also of importance in contact lens design. This paper presents results of the fitting of a conicoid equation to corneal shape data derived from a precision photokeratoscope. Both rotationally symmetric and non-rotationally symmetric forms of the conicoid equation were developed. The results show that if the cornea is regarded as a rotationally symmetric conicoid, the conicoid is ellipsoidal but with insufficient asphericity to eliminate spherical aberration for distance vision. More importantly, the results show that the cornea is significantly asymmetric in both radius of curvature and asphericity.