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J. P. Vande Geest, D. Yan; Influence of Scleral Microstructure on Lamina Cribrosa Strain - A Computational Study. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2134.
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The biomechanical behavior of ocular tissues such as the peripapillary sclera and lamina cribrosa (LC) may be involved in the onset and development of glaucoma. The microstructure (e.g., collagen orientation) of these tissues will undoubtedly play a major role in determining the ability of these tissues to protect the delicate optic nerve passing through the scleral canal. Our purpose here was to implement experimentally derived microstructural information into a microstructurally-based finite model of posterior ocular head tissues and use this model to parametrically investigate how alterations in scleral microstructure affect LC mechanical strains.
An axisymmetric finite element model of the posterior eye was constructed using geometry obtained from the literature and recorded measurements within our lab. Data from scleral biaxial tests were fit to a common microstructurally-based transversely isotropic strain energy (see Gasser et al., 2006) to arrive at a set of baseline material parameters. Material properties of the LC were assigned values one order of magnitude lower than those for the sclera. The dispersion parameter, Κ, the stress-like parameter, k1, and the fiber orientation, θ, were all varied independently.
The percentage change in LC maximum principal strain from the baseline simulation is shown in Figure 1. Fiber dispersion (30% decrease) and orientation (50% increase) of the scleral collagen both had significant affects on LC strain. The material parameter k1 had a relatively smaller effect on LC strain.
The orientation and degree of alignment of collagen fiber alignment in the peripapillary sclera is important in governing LC strain.
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