3D Solid Incompressible Viscoelastic Finite Element in Large Strains for the Cornea. Refractive Surgery Application

Abstract

Several models [1,2,3,4] have been developed in order to reproduce the corneal behavior in ophthalmological procedures as tonometry, radial keratotomy and photokeratectomy with Excimer Laser. It has been found that the viscoelastic effect of a biological soft tissue, as the cornea, is negligible in tonometry [5]. Nevertheless, clinical studies on humans showed refractive changes
with time in radial keratotomy. Wound healing is responsible for the long time effect (measured in years). On the other hand, the short-time effect (hours or days) has not been clarified.
In this work a 3D viscoelastic finite element model is developed taking into account incompressibility and large strains. An internal variable is introduced by means of a multiplicative decomposition of the deformation gradient. The final goal of the study is to determinate the importance of the viscoelastic effect in radial keratotomy.