Influence of the eye globe design on biomechanical analysis.

PURPOSE: To assess the mechanical contribution of inner eye components on corneal deformation during a finite element analysis.

METHODS: A finite element model of an eye globe was implemented to examine the corneal response under various mechanical conditions. The model incorporates the cornea, limbus, sclera, iris, lens, muscles, anterior chamber and vitreous. The Ogden hyperelastic model was used for the corneo-limbal region and the Yeoh isotropic model for the sclera. The anterior chamber was modelled as a cavity and other eye components were incorporated as linear elastic material. A fluid dynamic simulation was implemented to determine the spatial air puff velocity and pressure profiles around corneal surface.

RESULTS: The maximal apical displacement under IOP = 15 mmHg was 0.22 mm with a stress of 0.013 MPa. An unrestrained limbus slightly increases the apical displacement, while an unrestrained equatorial sclera largely increases the displacement by 10%, resulting in reduced stiffness. The iris slightly decreases the displacement but increases stress in the corneal periphery. Meanwhile, the joint contribution of muscle and lens cannot be neglected as it reduces corneal displacement by 50%. Incorporation of the remaining eye components results in nearly similar results. Under air puff loading, a free equatorial sclera raised the dynamic deformation amplitude by nearly 2%, while the dynamic profile remained similar for all remaining study cases considered.

CONCLUSION: In a finite element analysis, the lens, iris, and muscle each provide major mechanical contributions to corneal deformation, and it is highly recommended that the internal contributions are considered.