Finite element modelling of human eye lens

The human lens provides one-third of the ocular focussing power and is responsible for altering focus over a range of distances. This ability, termed accommodation, defines the process by which the lens changes its shape, in response to the movement of ciliary body, to adjust the refractive power. The accommodative ability gradually decreases with age such that around the fifth to sixth decades of life it is lost rendering the eye unable to focus on near objects. Current technologies are unable to effectively restore the requisite optical powers and accommodative ability of a presbyopic eye as the mechanism of accommodation is not fully understood. Plausible explanations, which are contradicted to each other, require definitive supports. Nevertheless, experimental evidences are difficult to obtain from living eye. Computational modelling serves as an alternative solution for the understanding of the physiological process of accommodation. An accurate and detailed model can closely simulate the in vivo behaviour of the eye lens. To date, the relevance of available models to the physiology needs to be further explored. The accuracy of any computational model highly depends on the input parameters. To build up a complete lens model one needs to seek resources from different studies and to assemble parameters of lenses from different subjects, which bring great challenges to this research field. The present work utilizes the Finite Element Analysis as the fundamental approach for investigating the mechanical and optical performances of lens models built at various ages based on input parameters from both in vivo and in vitro studies. The contributions of different ocular parameters to the accommodative loss are investigated i.e. the lens geometries, material properties, capsular thickness, capsular elasticity, zonular angles. Relations between two seemingly contradicting accommodative theories are demonstrated and possible explanations for the presbyopia are proposed.