Investigation of Corneal Biomechanical and Optical Behaviors by Developing Individualized Finite Element Model

Mengchen Xu, PhD Defense, Advised by Professor Geunyoung Yoon and Professor Amy L. Lerner

Hopeman 224

The biomechanics of the cornea has a significant impact on its optical behavior. Alterations in corneal biomechanics lead to abnormalities in the surface topography and affect ocular aberrations that degrade retinal image quality. The goal of this thesis work is aimed towards investigating the interaction of corneal biomechanical and optical behaviors through development of a corneal model. The model is developed based on the finite element method that accounts for individual variations in corneal geometry and material properties.

With this model, we studied the relative contribution of various geometrical and material parameters to corneal biomechanical and optical behaviors. We developed novel methods to characterize individual corneal material properties including the anisotropic collagen fibrils distribution, collagen fiber stiffness and nonlinearity using optical information to overcome the traditional challenges in corneal material characterization. The methods were validated through numerical simulations and ex vivo experiment. In addition, we also investigated the potential in vivo application of the material characterization methods by exploring the feasibility of controlling intraocular pressure (IOP) in vivo. A non-contact and non-invasive method was used to temporarily elevate IOP to multiple levels and the corresponding changes in corneal wavefront aberrations induced by the IOP elevations were measured.

The findings in this work provide scientific insights on the interrelation between corneal biomechanics and optics. Furthermore, the findings also provide great clinical implications in ophthalmic pathologies such as customized laser vision correction and the investigation of underlying mechanisms of other eye diseases such as keratoconus and ectasia.