Purpose:
To construct an automated FEA mesh generation algorithm capable of building the fiber ultrastructure of the human crystalline lens.
Methods:
An algorithm was designed in C++ and DirectX9 that built successive layers of fibers in a manner consistent with the known natural suture geometry of the lens based on Kuszak et al (2004). The model can be "grown" from the embryonic nucleus, layer by layer, to the outer cortex and lens capsule. The geometric constraints were identified and coded such that 3, 6 and 9 branch suture/fiber layers could be created with arbitrary fiber widths/thicknesses. The mathematical rules governing the placement of individual fiber bundles, such as the ratio of suture length to lens diameter and the ratio of anterior to posterior suture length, among many others, for each layer were derived such that a complete, anatomically based FEA model could be achieved. Additionally an algorithm was created to generate a variable thickness capsule model with appropriate zonule attachment points.
Results:
The algorithms described were used to create FEA models with various configurations of welded and free-sliding fiber geometries. The models were exercised using LS-DynaTM and provided a mechanism to study fiber dynamics under accommodative loads and their contribution to the shape change of the refractive surfaces of the lens.
Conclusions:
Computer automated fiber mesh generation algorithms provide a novel way to build FEA lens models in order to examine the contributions of each aspect of the lens fiber ultrastructure.