Influence of Sex on Neuroretinal Degeneration: Six-Month Follow-Up in Rats With Chronic Glaucoma

Abstract

PURPOSE. To evaluate differences by sex in the neuroretina of rats with chronic glaucoma over 24 weeks of follow-up, and to assess by sex the influence on neurodegeneration of different methods of inducing ocular hypertension. METHODS. Forty-six Long–Evans rats—18 males and 28 females—with induced chronic glaucoma were analyzed. Glaucoma was achieved via 2 models: repeatedly sclerosing the episcleral veins (9 male/14 female) or by injecting poly(lactic-co-glycolic acid) micro-spheres measuring 20 to 10 μm (Ms20/10) into the anterior chamber (9 male/14 female). The IOP was measured weekly by tonometer; neuroretinal function was recorded by dark/light-adapted electroretinography at baseline and weeks 12 and 24; and structure was analyzed by optical coherence tomography using the retina posterior pole, reti-nal nerve fiber layer and ganglion cell layer protocols at baseline and weeks 8, 12, 18, and 24. RESULTS. Males showed statistically significant (P < 0.05) higher IOP in both chronic glaucoma models, and greater differences were found in the episcleral model at earlier stages. Males with episclerally induced glaucoma showed a statistically higher increase in retinal thickness in optical coherence tomography recordings than females and also when comparing Ms20/10 at 12 weeks. Males showed a higher percentage of retinal nerve fiber layer thickness loss in both models. Ganglion cell layer thickness loss was only detected in the Ms20/10 model. Males exhibited worse dark/light-adapted functionality in chronic glaucoma models, which worsened in the episcleral sclerosis model at 12 weeks, than females. CONCLUSIONS. Female rats with chronic glaucoma experienced lower IOP and structural loss and better neuroretinal functionality than males. Sex and the ocular hypertension–inducing method influenced neuroretinal degeneration.