Metformin for the Minimization of Geographic Atrophy Progression in Patients With AMD

Inclusion Criteria: * Subject must be \>/= 55 years of age * Subject must have evidence of advanced dry AMD, defined by the characteristic presence of drusen and/or pigmentary changes as well as geographic atrophy * Subject must have clear ocular media and adequate pupillary dilation * Subject must be able to swallow capsules * Study eye must have best corrected visual acuity (BCVA) of 20/20-20/400 * Subject must be willing and able to pay for monthly prescription of Metformin HCl for 18 months in the event that their insurance carrier will not cover the cost of the drug Exclusion Criteria: * Subjects with insufficient baseline size of geographic atrophy, less than 1.25 mm2 (0.5 Macular Photocoagulation Study Disc Areas). GA is defined as one or more well-defined and often circular patches of partial or complete depigmentation of the RPE, typically with exposure of underlying choroidal blood vessels. Even if much of the RPE appears to be preserved and large choroidal vessels are not visible, a round patch of RPE partial depigmentation may be classified as early GA. The GA in the study eye must be able to be photographed in its entirety, and it must not be contiguous with any areas of peripapillary atrophy, which can complicate area measurements. * Subjects who are already taking metformin for another purpose * Subjects with type 1 or 2 diabetes * Subjects with compromised kidney function: * Serum creatinine ≥1.5 mg/dL for males and ≥1.4 mg/dL for females * Subjects with moderate to severe heart failure (Class III or IV, New York Heart Association Functional Classifications) * Subjects with Child's class C cirrhosis * Evidence of retinal atrophy due to causes other than atrophic AMD. * Subjects who have had anti-VEGF injections or active choroidal neovascularization in the study eye during the last 12 months * Current evidence or history of ocular disorders in the study eye that in the opinion of the investigator confounds study outcome measures, including (but not limited to): 1. Non-proliferative diabetic retinopathy involving 10 or more hemorrhages or microaneurysms, or active proliferative diabetic retinopathy 2. Branch or central retinal vein or artery occlusion 3. Macular hole 4. Pathologic myopia 5. Uveitis 6. Pseudovitelliform maculopathy 7. Intraoperative surgery within the last 90 days prior to study eye enrollment