Modeling the biomechanics of the human cornea accounting for local variations of the collagen fibril architecture

We present a finite element model of the human cornea describing the in-plane organization of the stromal collagen, modified variously to include features of the collagen architecture. We investigate numerically the implication of the local organization of collagen in the stroma on the response of the human cornea to mechanical tests. We compare four different models by simulating three ideal mechanical tests, i. e., the ex-vivo inflation test, the in-vivo probe indentation, and the in-vivo air puff tests. Numerical results show slight differences between the models in terms of global response and stress distribution. Differences in the overall mechanical response are observed in dynamic tests, while quasi-static tests are not able to differentiate between the models. Stress distributions differ markedly when a variation of the shear stiffness across the thickness is considered. We conclude that the actual architecture of the collagen across the thickness of the cornea or at the limbus has a minor relevance from the mechanical point of view with respect to the main anisotropic orthogonal collagen structure that has been considered and acknowledged in the literature.