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Rafael Grytz, Kapil Krishnan, Vincent Libertiaux, Christopher A Girkin, J Crawford C Downs; Incorporating Realistic Anisotropic and Heterogeneous Material Properties Into Eye-Specific Multi-Scale Models of the Human Optic Nerve Head. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2458.
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© ARVO (1962-2015); The Authors (2016-present)
Commercial finite element (FE) modeling packages do not have the tools necessary to effectively incorporate the complex anisotropic and heterogenous material properties typical of the optic nerve head (ONH) and sclera. We developed a new mesh-free approach to incorporate realistic material properties into eye-specific ONH FE models.
Eye-specific FE models of five human ONHs were created from 3D reconstructions of the ONH connective tissues acquired using a microtome-based serial sectioning and block face imaging device. The models include the sclera, lamina cribrosa, pre- and retro-laminar tissues, retina, and pia. Anisotropic material properties were defined at convenient locations (control points) at which anisotropic material directions could be identified based on the reconstructed tissue micro- or macro-structure. Otherwise their locations were arbitrary and independent of the FE mesh. We used a mesh-free approach to interpolate the anisotropic and heterogeneous material properties from the control points into the FE models.
It was convenient to define anisotropic orientations at the anterior and posterior scleral surface based on the eye-specific geometry of each sclera. The mesh-free approach was effective in interpolating these orientations across the scleral thickness and between the control points (Fig B,C). The interpolated properties allowed the effective modeling of the anisotropic circumpapillary ring of collagen fibers in the sclera, while following the eye-specific anatomical features of the individual eye (Fig D). Similar eye-specific results were obtained for the pia. For the lamina cribrosa, anisotropic material properties were directly obtained from the 3D reconstructions of its micro-structure and were effectively interpolated across the laminar elements using our mesh-free approach (Fig. E).
We have developed a new software tool to effectively incorporate complex anisotropic and heterogeneous material properties that are either estimated at convenient locations or directly obtained from the tissues’ micro-structure into eye-specific FE models. The approach should simplify future studies to elucidate the role of biomechanical factors and optic nerve head remodeling in glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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