Oral Metformin for Treatment of ABCA4 Retinopathy

This study is testing whether oral metformin — a well-known and widely used diabetes drug — can slow the progression of Stargardt disease, a rare inherited form of macular degeneration caused by mutations in the ABCA4 gene. Stargardt disease causes progressive loss of central vision, typically beginning in childhood or young adulthood, and there is currently no approved treatment that slows its progression. Laboratory research suggests that metformin may activate a protective cellular pathway (AMPK) that clears toxic waste products that build up in the retina and damage photoreceptors. Participants will take metformin daily and have their retinal health carefully tracked over time using specialized eye scans to see whether the rate of vision loss slows down compared to their own natural history data. You may be eligible if: - You are at least 12 years old - You have confirmed ABCA4 mutations and a typical Stargardt disease diagnosis in both eyes - You have at least 2 years of natural history data showing the rate of your retinal cell loss - You are not currently taking metformin and have not taken it during the natural history period You may NOT be eligible if: - You are pregnant or breastfeeding or planning to become pregnant during the study - You have chronic kidney impairment (eGFR below 45) or severe heart, liver, or lung disease - You have Type 1 diabetes - You have a history of chronic lactic acidosis or diabetic ketoacidosis - You have a known allergy to metformin - You have mutations in PRPH2, PROM1, or ELOVL4 genes - You have choroidal neovascularization (retinal scarring) in either eye Talk to your doctor to see if this trial is right for you.