Sex, Glaucoma, and Iris Biomechanics

Abstract

In this dissertation the critical intersections of sex biases in biomechanics research, particularly in the biomechanics of glaucoma – a leading cause of blindness that disproportionately affects women – were investigated. First, we delineated the pattern of sex representation in biomechanics research by analyzing abstracts submitted to a major conference and uncovered trends and biases in the inclusion of both sexes in study samples. We then experimentally characterized the elastic modulus of the iris stroma in female and male porcine samples ex vivo, utilizing micro-indentation techniques.

The complex pathophysiology of primary angle-closure glaucoma (PACG) is significantly influenced by the mechanical properties of the iris. Given the higher incidence of PACG in women and prior evidence of increased iris stiffness in PACG patients, we hypothesized that the elastic modulus will

be significantly greater in female irides compared to male samples. Additionally, recognizing that the intrinsic behaviors of soft tissues can vary significantly under different environmental conditions, we investigated the effects of factors such as temperature and hydration on the mechanical properties of the iris. Finally, we employed inverse finite element analysis to quantify in-vivo iris stiffness in human subjects from both healthy and PACG groups, stratified by sex. We utilized clinical imaging and computational modeling to assess mechanical properties of the iris. Given the aforementioned reasons, we hypothesized that female subjects would exhibit significantly greater iris stiffness. This nuanced approach aimed to reveal how sex-specific differences in iris mechanics could potentially influence both the risk and progression of glaucoma, thereby offering insights that could refine diagnostic and therapeutic strategies for PACG. Our findings underscore the necessity of incorporating sex as a biological variable in biomechanics research and strive to bridge the knowledge gap in how sex differences affect the biomechanics of ocular tissues. By integrating clinical and pre-clinical findings, we aim to inform more precise and effective treatments that improve outcomes for patients with vision impairments from PACG.