Preliminary computer simulation of the effects of radial keratotomy.

We created a computerized mathematical model of the eye for the simulation of refractive surgery. This model used a slightly prolate shape for a moderately myopic eye and an idealized aspheric profile for the cornea. The finite element method and the nonlinear Mooney-Rivelin law were used to analyze stress-strain relationships. Radial keratotomy changes stress distribution in the cornea and the anterior sclera, with major changes at the paracentral and peripheral ends of the incisions. The model predicted that there would be a flattening of the central cornea with a posterior displacement, which increased with an increase in intraocular pressure. A change in the length of the incision of 0.5 mm produced a significant change in correction. For small clear zones (3 to 4 mm), incisions of equal length produced comparable changes in refraction. We found that the effect of the corneal radius of curvature on the amount of refractive change was negligible. We studied the effect of elasticity coefficients and corneal anisotropia.