Mechanical Behaviour of the Lens Capsule

Harvey Burd

The capsule of the lens forms a key element of the accommodation apparatus in the natural human lens. In addition, the capsule plays an important role in certain proposed surgical procedures (e.g. accommodating IOLs) for improving the accommodation performance of presbyopes. Research is underway in Oxford in collaboration with Prof. Rich Regueiro of the University of Boulder, Colorado on the development of new constitutive models for the lens capsule. These models are needed to develop improved finite element models of the entire lens.

 structuralmodel

Structural model of the lens capsule (Burd 2009)

 

One approach that is being explored is to develop modelling procedures that are based on the microstructure of the collagen IV network that exists in the lens capsule. In this modelling approach, the overall mechanical performance of the capsule is represented by a network of non-linear bars (representing the network of collagen IV in the capsule) embedded in a neo-Hookean matrix (to represent the matrix of proteoglycans and glycoproteins). Details of this structural model are given in Burd (2009). An animation, showing typical deformations induced in the collagen network when the model is stretched, is available here. A suite of Matlab functions to implement the model in Burd (2009) is available on an open-source basis. Send an email to Harvey Burd for further details.

This structural model has recently been incorporated in the finite element program Oxfem_hyperelastic to provide a multiscale model of the accommodation process.This implementation is described in Burd & Regueiro 2015.

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