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Excerpt:
IntroductionAge-related vision loss from macular degeneration (AMD), glaucoma, and diabetic retinopathy (DR) is often tied to the biology of aging. Researchers are now exploring whether drugs known to affect aging – dubbed geroprotectors – might also protect the eye. In particular, medications like metformin, rapamycin (and related “rapalogs”), SGLT2 inhibitors, acarbose, and new senolytics have drawn attention. These agents influence key aging pathways such as the mTOR signaling network, autophagy, mitochondrial health, and cellular senescence. Here we review what is known about these geroscience drugs and their impact on AMD, glaucoma, and DR – summarizing population studies, laboratory experiments, and early trials. We then contrast observational signals with intervention data and suggest priorities for future eye-focused trials.Metformin and Eye HealthMetformin is a widely used diabetes medication that also activates AMP-activated kinase (AMPK), mimics calorie restriction, and can reduce cellular stress. It influences autophagy (the cell’s cleanup process), improves mitochondrial function, lowers inflammation, and even affects senescent cells () (). These actions suggest potential benefit for age-related eye diseases. Metformin and AMDObservational studies suggest metformin users have lower AMD rates. A recent meta-analysis of over 2.6 million people found metformin use was associated with about a 14% reduced odds of developing AMD (). The benefit appeared in both diabetic and non-diabetic individuals. For example, a large Chinese retrospective study found only 15.8% of long-term diabetic metformin users had AMD versus 45.2% of non-users (). In mice with AMD-like retina damage, diabetes treatment with metformin slowed retinal degeneration (similar to rapamycin in OXYS rats) (). However, a randomized trial-like follow-up of a diabetes prevention study found no difference in AMD rates between metformin-treated and control groups after 16 years (). This shows observational signals can be misleading: biases in who gets metformin (e.g. younger, healthier diabetics) might explain part of the apparent benefit. Thus, despite many studies hinting at protection, the only long-term trial data do not confirm a metformin effect on AMD.Metformin and GlaucomaSeveral large studies have associated metformin with lower glaucoma risk. In a Dutch population study, diabetic patients on metformin had far lower open-angle glaucoma incidence than diabetics untreated (lifetime risk ~1.5% vs. 7.2% in non-diabetic peers) (). In a U.S. cohort of 18,000 diabetics, metformin users had about one-third the odds of developing glaucoma as non-users (). Mechanistic research supports this: in mice with retinal injury, metformin preserved retinal ganglion cells (which form the optic nerve) by stimulating autophagy and mitochondrial quality control () (). Clinically, diabetics with glaucoma on metformin showed no visual-field decline over 6 months, whereas those on insulin did deteriorate (). Yet not all studies agree. A six-year follow-up of an Indian eye cohort saw no difference in glaucoma incidence between diabetic metformin users and non-users (). Differences in populations, diabetes control, and glaucoma definition may explain the mixed results. In summar
