Effects of Aging and Early-Onset Menopause on Intraocular Pressure (IOP) and Aqueous Humor Conventional Outflow Facility

Biomechanical factors play a crucial role in glaucoma development, the world-leading cause of irreversible blindness. Although age is known to affect the tissues? biomechanical properties, early-onset menopause has recently been associated with the risk of developing glaucoma, and the effects of aging relative to early-onset menopause on eye?s biomechanical factors remain underexplored. This work?s goals were to study the effects of aging and early-onset menopause on intraocular pressure (IOP), aqueous humor outflow facility, and ocular compliance. Female Brown Norway rats underwent Sham or surgical menopause (ovariectomy; OVX) at 3-4 months of age and were split into young (5-6 months) or middle-aged groups (9-10 months). We monitored IOP until the established aging time points and performed ex vivo biomechanical measurements via the iPerfusion system. IOP was higher for the middle-aged Sham and OVX animals by 25% and 35%, respectively (p<0.001), when compared to their respective initial IOPs. Furthermore, middle-aged OVX animals had a 11% higher IOP compared to Sham animals (p=0.005), and a 20% lower outflow facility (p=0.031). Ocular compliance decreased with age in the Sham (24.9%, p=0.011) and OVX (24.5%, p=0.005) cohorts and by 24.1% independent of cohort (p=0.0001). Elucidating the effects of age and early-onset menopause on biomechanical factors that contribute to glaucoma pathology is necessary to help move the field forward and preserve the eyesight of millions of patients.