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P. J. Missel; Finite Element and Finite Volume Simulations of Drug Diffusion and Partitioning in the Eye: Mathematical Validation of an Anatomically Accurate Ocular Model. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5832.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the accuracy of simulations of ocular drug delivery.
A geometric rabbit eye model with a hemispherical drug source in the center was constructed using a preprocessor (GAMBIT) compatible with both finite element (FIDAP) and finite volume (FLUENT) codes. The steady state drug concentration profile was solved assuming the device surface was at the solubility limit and drug is eliminated from the choroid, allowing for disparate assignments of diffusion and partition coefficients in each tissue region. With perfect spherical symmetry in the rear portion, with concentric shells for sclera, choroid, and retina and vitreous, it was possible to derive an exact algebraic expression (Mathematica) for the steady-state drug concentration distribution along the optical axis for a limited set of assignments of diffusion and partition coefficients. Partitioning was implemented using the PINTERFACE facility (FIDAP) or by a user-defined function (FLUENT).
Both codes reproduced the exact concentration profile with discontinuities at interfaces between tissues having different partitioning. Only FLUENT has the ability to refine the geometric mesh in regions where the concentration changes rapidly with distance (such as near inter-tissue boundaries), producing a profile more closely agreeing with the exact solution.
Having obtained an accurate result for a geometry for which an exact solution is known, we have confidence that the software can accurately predict drug distributions from devices of arbitrary placement and geometry.
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