What if a tablet taken every day for diabetes also helped protect eyesight? A team from the University of Liverpool has just shown that a very ordinary drug,
metforminseems linked to a lesser progression of one of the main causes of blindness among seniors.
AMD: leading cause of blindness in people over 65
Age-related macular degeneration (AMD) is a condition that affects the macula, the central area of the retina at the back of the eye. We distinguish two forms:
- Wet AMD is characterized by the growth of new, abnormal blood vessels under the retina. Blood can seep through their walls, causing macular edema. Sometimes this also leads to retinal hemorrhages. The wet form, rarer but rapid, can be slowed down thanks to intraocular injections;
- In atrophic AMD (or dry form, which represents 9 out of 10 cases), the photoreceptors of the macula deteriorate little by little, followed by the cells of the retinal pigment epithelium. This phenomenon leads to the formation of increasingly larger holes in the macula, visible during a simple examination of the retina (fundus). This process is slow, usually taking between five and ten years before the patient loses central vision. To date, no treatment is available in Europe for this form of AMD.
This pathology gradually destroys the macula, a tiny area of the retina that allows us to read, drive or recognize faces. In rich countries, its intermediate and advanced forms affect 10 to 15% of people over 65 and constitute the leading cause of blindness.
Less AMD on metformin
There metformin is one of the most prescribed treatments for type 2 diabetes, taken daily in tablet form. Studies also attribute “anti-aging” effects to it: antioxidant and anti-inflammatory action, slowing down the formation of new vessels and stimulation of cellular cleansing mechanisms, all involved in AMD. Large observational studies and meta-analyses already suggested a lower risk of AMD in people taking metformin.
To test this signal, Liverpool researchers analyzed fundus photos of 2,089 people aged over 50 with type 2 diabetes, followed in the local diabetic retinopathy screening programme. About 40% took metformin, 60% did not, and all were seen again five years later with a new retinal image.
The images were classified into absence of AMD, early, intermediate or late form according to a standardized grid, then the two groups compared taking into account age, sex, duration and control of diabetes, and retinopathy. After five years, people on metformin were 37% less likely to develop intermediate AMD. No clear association was found for early AMD nor for progression to late forms, where cases remained rare.
Towards a new treatment avenue?
The authors point out that this is only a statistical association, in a study where metformin was not given at random but according to the patients’ profile, and call for clinical trials before any routine use. As Dr. Nick Beare, ophthalmologist, summarizes: “Most people who suffer from AMD have no treatment, so this is a big step forward 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 the sight of many people“.