A theoretical model of the cornea as a thin shell of variable thickness in relation to radial keratotomy

Abstract

A theoretical study of the deformation fields of the cornea under internal pressure is presented. The general elasticity equations describing a thin shell of variable thickness are solved using finite difference techniques. To gain insight into the natural corneal structure, the constant thickness case is compared to one of normal thickness. The bending stresses are found to influence the cornea's natural curvature. In the third case, the normal thickness is increased 10% to model the edematous state resulting from the incisions made during radial keratotomy. A comparison of the third case reveals the increased thickness in the peripheral cornea makes a minor contribution to the displacement; but moreover, the curvature change is opposite to that desired from radial keratotomy. The incisions are necessary to weaken the lateral support of the shell allowing the displacement and change in curvature which corrects myopia.