Effects of Stress and Strain on the Optic Nerve Head on the Progression of Glaucoma

Précis: In primary open-angle glaucoma, the rate of retinal nerve fiber layer thickness decrease was negatively correlated with lamina cribrosa strain, which was associated with intraocular pressure and optic nerve head geometric factors. Purpose: We hypothesized that the biomechanical deformation of the optic nerve head (ONH) contributes to the progression of primary open-angle glaucoma (POAG). This study investigated the biomechanical stress and strain on the ONH in patients with POAG using computer simulations based on finite element analysis (FEA) and analyzed its association with disease progression. Methods: We conducted a retrospective analysis that included patients diagnosed with early-to-moderate stage POAG. The strains and stresses on the retinal nerve fiber layer (RNFL) surface, prelaminar region, and lamina cribrosa (LC) were calculated using computer simulations based on FEA. The correlations between the rate of RNFL thickness decrease and biomechanical stress and strain were investigated in both the progression and non-progression groups. Results: The study included 71 and 47 patients in the progression and non-progression groups, respectively. In the progression group, the factors exhibiting negative correlations with the RNFL thickness decrease rate included the maximum and mean strain on the LC. In multivariate analysis, the mean strain on the LC was associated with optic disc radius, optic cup deepening, axial length, and mean intraocular pressure (IOP), whereas the maximum strain was only associated with mean IOP. Conclusions: In early-to-moderate stage POAG, the rate of RNFL thickness decrease was influenced by both the mean and maximum strain on the LC. Strains on the LC were associated with mean IOP, optic disc radius, axial length, and optic cup deepening. These results suggest that not only IOP but also ONH geometric factors are important in the progression of glaucoma.