Biomechanics and Ultrastructure of the Ocular Lens

Study of the biomechanics of the ocular lens is imperative to increasing our understanding of the role of the ocular lens in accommodation, to improving current surgical methods (cataract and intraocular lens replacement), and to better qualify the nature and mechanics of injuries sustained to the ocular lens (lens dehiscence, lens perforation, and traumatic cataract). Previous work done to determine and model the mechanical properties of the ocular lens includes non-ideal experimental assumptions and lack of qualified data. The goal of this work is to produce and analyze data suitable for the creation of an ultrastructurally based computational model of the ocular lens and make progress toward the generation of such a model. The creation of a model requires the determination of the material properties as well as identification of the ultrastructure of the tissue to be modeled. Unconfined compression testing of the whole porcine ocular lens, puncture testing of the whole porcine ocular lens, and nanoindentation of the anterior porcine and human lens capsule were performed to generate data from which to calculate material properties of the lens. Cryo-electron tomography and confocal LASER scanning microscopy were employed to determine the ultrastructure of the porcine lens capsule and porcine lens fiber cells, respectively. Test data were produced from the mechanical tests and the fitting of parameters to calculate material properties were started. Potential identification of the type-IV collagen meshwork of the lens capsule and positive identification of the lens fiber cells were achieved. Preliminary modeling work was started with the data available using Abaqus (simulia.com) and Tahoe (tahoe.sourceforge.net)