Abstract
Abstract: :
Purpose:To create a physics–based finite element model of the eye and simulate corneal deformation and the resulting astigmatism induced by incisions for cataract surgery. Methods:A three dimensional finite element model of the eye was constructed by segmenting the cornea, sclera, lens, vitreous, muscles, and associated adnexal structures from the Visible Human Female dataset. The structures were manually segmented from 110 serial axial histological images of the orbit with 0.33mm slice thickness and 0.33mm in–slice resolution. A volumetric tetrahedral mesh was generated from the segmentation using CUBIT, an automatic mesh generation program developed at Sandia National Lab. In the finite element simulations, a linear elastic model was applied to all adnexal structures except the cornea. The stiffness (Young's modulus) of each modeled tissue type was estimated based on the available literature. Poisson's ratio for all structures was estimated to be 0.495, indicating near incompressibility. For the cornea, both linear elastic and non–linear hyperelastic models were applied. Multiple simulations were created that employed these different corneal tissue models, and the results of the simulations were compared to observed tissue deformations. Results:Tissue deformations created by simulated incisions of the finite element model were consistent with clinically observed post–surgical astigmatism. The simulations produced using non–linear models of cornea tissue provided a better approximation than the linear elastic model of the observed astigmatism following corneal incisions. Conclusions:Finite element analysis is a useful tool for modeling surgical effects on the cornea and developing a better understanding of the mechanics of the cornea. The creation of patient–specific simulations would allow surgical outcomes to be predicted based on individualized finite element models. Future work will compare the predictive capability of patient–specific finite element models to current formulas.
Keywords: computational modeling • astigmatism • wound healing