A cheap, widely used diabetes medication may also help protect against the most common cause of blindness in the western world, according to a study published in in BMJ Open Ophthalmology.
Scientists at the University of Liverpool, UK, discovered that people with diabetes who took metformin were 37% less likely to progress to an intermediate stage of age-related macular degeneration (AMD) over a five-year period, compared to those not taking the drug.
AMD is a disease affecting the central part of the retina at the back of the eye. As it progresses, it causes the light-sensitive tissue to break down, leading to the loss of central vision and, eventually, blindness. It affects between 10 and 15% of people over the age of 65 in the UK (up to 1.8 million people) and is the leading cause of blindness in high-income countries. The condition costs the UK an estimated £11.1 billion a year.
Currently, the options for treating AMD are limited. One form of the disease known as geographic atrophy, or “dry” AMD has no approved treatment in Europe. The other main form, “wet” AMD, can be treated but the treatment involves repeated injections into the eye and is expensive.
That is what makes these findings so significant. Metformin is an inexpensive, off-patent tablet that is used as a first-line treatment for type 2 diabetes. It costs around £50 per patient per year on the NHS. Beyond its effects on blood sugar, it is also known to have anti-ageing properties, acting as an antioxidant and reducing inflammation in the body.
The study was based on eye photographs taken from around 2,000 people attending routine diabetic eye screening in Liverpool over five years. Researchers assessed whether AMD was present and how advanced it was, then compared outcomes between those taking metformin and those who were not, adjusting for factors such as age, sex and how long they had had diabetes.
While a possible link between metformin and AMD has been suspected before, this is the first study to assess AMD directly from eye photographs rather than relying on GP records or insurance claims, making it a more reliable measure of the condition.
“Most people who suffer from AMD have no treatment, so this is a great breakthrough in our search for new treatments. What we need to do now is test metformin as a treatment for AMD in a clinical trial. Metformin has the potential to save many people’s sight,” said Dr Nick Beare, the eye doctor who led the research.
The next step will be to test metformin specifically as an AMD treatment in a formal clinical trial, to confirm whether the protective effect seen in this study holds up under more rigorous testing.
Romdhoniyyah DF, Alshukri A, Parry DG, Harding S, Beare NAV. Metformin and incidence of age-related macular degeneration in people with diabetes: a population-based 5-year case-control study. BMJ Open Ophthalmology. 2026;11:e002339. https://doi.org/10.1136/bmjophth-2025-002339