Finite Element Model of Cornea Deformation

Abstract

Abstract. Cornea surgeons have observed that changes in cornea curvature can follow cataract surgery and cause astigmatism. The placement of surgical incisions has been shown to influence these curvature changes. Though empirical data has been collected about this phenomenon, a biomechanical model has not been employed in predicting post-surgical outcomes. This work implemented an incised finite element model of the eye to investigate factors influencing corneal shape after surgery. In particular, the effects of eye muscle forces and intra-ocular pressure were simulated. Cornea shape change was computed via finite element analysis, and the resulting change in cornea curvature was measured by fitting quadratic curves to the horizontal and vertical meridians of the cornea. Results suggest that these two sources of deforming force counteract each other and contribute to astigmatism in perpendicular directions.

Biomechanical analysis of the keratoconic cornea

“…The assumption of linear elasticity is consistent with the previous assumption of small deformations, and has been used in previous models (e.g. Crouch et al (2005) and AsejczykWidlicka et al (2007)). The assumption of orthotropic material behavior is a progress over previous work, and is taken to explore the possibility that softening of the cornea at certain material directions contributes to keratoconus, as described later in the paper.…”

“…The following general assumptions were made: (i) The normal unloaded cornea is assumed to be symmetric, half-sphere shaped at the central region, and clamped at the sclera, which is a reasonable approximation of the shape of the real healthy cornea, that has been adopted in several previous corneal models (Anderson et al, 2004;Crouch et al, 2005;Djotyan et al, 2006). (ii) Corneal tissue deformations under the IOP values considered in this paper (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) are relatively small compared with the cornea's radius of curvature, an assumption supported by the experimental data of Pierscionek et al (2007).…”

Hydrodynamic Analysis and Irrigation Device Design for the Coaxial and Bimanual Phacoemulsification Techniques in Cataract Surgery

“…This coupled-flow finite element model does not cover cataract surgery. An approximation relating to cataract surgery was developed in order to predict changes in the corneal curvature after surgery based on investigations into the material properties of the cornea (Crouch et al, 2005). A linear elastic material model was used for the entire eye.…”

Deformation and Smooth Joining of Mesh Models for Cardiac Surgical Simulation

“…So it is difficult for FFD to manage geometrical constraints defined on the mesh in surgical simulation. FEM [2,4,15] offers accurate and realistic modeling of soft tissue deformation. However, it is computationally too expensive for real-time or near-real-time simulation.…”

“…In predictive surgical simulation [2,4,15], 3D models of body tissues may deform according to applied forces or geometrical constraints on the body tissues. The simulation system predicts surgical results given minimum user inputs.…”