Modeling the relation between intraocular pressure and human trabecular meshwork fluid-mechanical properties

Elevated introcular pressure (IOP) is a major risk factor for primary open angle glaucoma (POAG), the second leading cause of blindness worldwide. In this article, we investigate the relation between IOP increase and fluid-mechanical properties of the trabecular meshwork (TM), which is the main pathway of aqueous humor (AH) outflow in the human eye. TM is represented as an axisymmetric deformable biphasic porous medium (solid and fluid) with hydraulic permeability nonlinearly depending on the local AH pressure. Solving Darcy's law provides a TM hydraulic resistance (TMR) depending on the radial pressure drop, while TM stiffness is included multiplying the TMR by a shape function of TM Young's modulus constructed using postmortem measurements of human eye outflow facility. Simulations of AH flow based on an electric equivalent scheme of the eye indicate that TMR increases with TM stiffness, leading to a progressive increase of IOP until over the upper limit of the normal IOP range. The obtained results shed light on the impact of microscopic properties of the eye on its macroscopic function, and support the integration of experimental studies, mathematical modeling, and data analysis to develop an optimized patient-specific therapy to cure POAG.