Background: It has been proposed that in the absence of a blood supply, the ocular\r\nlens operates an internal microcirculation system. This system delivers nutrients,\r\nremoves waste products and maintains ionic homeostasis in the lens. The\r\nmicrocirculation is generated by spatial differences in membrane transport\r\nproperties; and previously has been modelled by an equivalent electrical circuit and\r\nsolved analytically. While effective, this approach did not fully account for all the\r\nanatomical and functional complexities of the lens. To encapsulate these\r\ncomplexities we have created a 3D finite element computer model of the lens.\r\nMethods: Initially, we created an anatomically-correct representative mesh of the\r\nlens. We then implemented the Stokes and advective Nernst-Plank equations, in\r\norder to model the water and ion fluxes respectively. Next we complemented the\r\nmodel with experimentally-measured surface ionic concentrations as boundary\r\nconditions and solved it.\r\nResults: Our model calculated the standing ionic concentrations and electrical\r\npotential gradients in the lens. Furthermore, it generated vector maps of intra- and\r\nextracellular space ion and water fluxes that are proposed to circulate throughout\r\nthe lens. These fields have only been measured on the surface of the lens and our\r\ncalculations are the first 3D representation of their direction and magnitude in the\r\nlens.\r\nConclusion: Values for steady state standing fields for concentration and electrical\r\npotential plus ionic and fluid fluxes calculated by our model exhibited broad\r\nagreement with observed experimental values. Our model of lens function\r\nrepresents a platform to integrate new experimental data as they emerge and assist\r\nus to understand how the integrated structure and function of the lens contributes\r\nto the maintenance of its transparency.
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