Stresses and fluid flow in lamina cribrosa through anisotropic poroelasticty

TL;DR

This study develops an anisotropic poroelastic model of the lamina cribrosa to analyze how intraocular pressure affects tissue stress, strain, and fluid flow, providing insights into glaucomatous damage mechanisms.

Contribution

It introduces a transversely isotropic poroelastic model of the lamina cribrosa based on Reissner Mindlin plate theory, linking mechanical deformation and blood flow under glaucoma conditions.

Findings

Stress and shear strain peak in the peripheral LC region.

Fluid content decreases as intraocular pressure increases.

Material anisotropy affects fluid content and shear strain estimates.

Abstract

To explore the possible mechanical correlations between intraocular pressure (IOP) variations and glaucoma, this study presents a transversely isotropic poroelastic model of the Lamina Cribrosa (LC) based on Reissner Mindlin plate theory, ultimately highlighting the interplay between solid matrix deformation and blood flow behavior under pathological conditions. Starting from poroelasticity theory, the equilibrium equations governing the LC were formulated and analytically solved by applying appropriate mechanical and hydraulic boundary conditions. The results indicate that both strain and stress measures (in the form of shear strain and von Mises stress) peak in the peripheral region of the LC, which is currently suspected to be the initial site of glaucomatous damage. These quantities increase with IOP, suggesting a pressure-dependent mechanical insult to the retinal ganglion cell (RGC) axons. In parallel, the model predicts a monotonic reduction in fluid content as IOP rises, which may contribute to ischemic phenomena and disc haemorrhages. The influence of material anisotropy was also examined, revealing that isotropic assumptions tend to underestimate the fluid content while overestimating shear strain. Given the current experimental challenges in measuring blood flow within the LC, the proposed model provides a valuable framework for exploring the coupled mechanical hemodynamic behavior of the tissue and for inverse estimation of its mechanical parameters, such as the stiffness of the opening for the central retinal vessels.