The application of fracture mechanics to radial keratotomy

The use of mathematical models to predict material behavior is a means by which material characteristics can be evaluated without having to wait years to see results. The following is a proposed model to evaluate the effect ocular pressure change, due to glaucoma, has on the fracture parameter K_I. The model was developed to characterize the mechanical integrity of the cornea using a well accepted linear elastic fracture mechanic parameter K_I. The model was developed using standard K-solutions for selected cracked configurations. Three different cracked configurations were utilize, a crack in a sphere, in-line cracks, and cracks that lie parallel to one another. The solutions were combined to arrive at the final model. This model shows that the incision length reduces the stress allowable to cause failure. Yet, it also shows that if the ocular pressure increases above the normal range, 10-20 mm Hg, to glaucoma pressures between 60-80 mm Hg, and maintains a constant pressure, corneal failure will not occur