A large retinal imaging study suggests Metformin Use in Diabetes Patients with type two diabetes who take metformin have significantly lower odds of developing intermediate age-related macular degeneration, though researchers say clinical trials are needed to confirm a protective effect.
Study Finds Lower Risk in Intermediate Disease Stage
Researchers analyzing retinal images from more than 2,000 diabetes patients found that metformin use was associated with about a 37% reduction in the odds of developing intermediate age-related macular degeneration, or AMD, over five years.
The findings, published in BMJ Open Ophthalmology, come from a retrospective analysis of prospectively collected screening data in Liverpool, England. The study followed participants aged 50 and older who underwent routine retinal photography between 2011 and 2016.
“This association between Metformin Use in Diabetes Patients and a reduced risk of AMD is statistically significant, but it does not establish causation,” the authors wrote, describing the results as hypothesis-generating rather than definitive.
Intermediate AMD represents a critical stage of disease progression, marked by structural retinal changes that increase the risk of sight-threatening vision loss.
Imaging-Based Data Strengthen Observational Evidence
The study drew on data from the Individualised Screening for Diabetic Retinopathy program, a population-based screening initiative. From an initial cohort of 2,600 participants with clinically confirmed type two diabetes, researchers analyzed usable images from 2,089 individuals.
Participants received retinal fundus photography at baseline and again after five years. Images were graded using a modified Age-Related Eye Disease Study classification system, which categorizes AMD severity as none, early, intermediate, or late.
Lead author Dr. Sarah Mackenzie said the use of retinal images addressed a key limitation of prior studies. helping clarify how Metformin Use in Diabetes Patients relates to disease staging and progression. “Most previous research relied on insurance claims, which do not reliably capture disease stage or progression,” she said.
Statistical models adjusted for age, sex, diabetes duration, glycated hemoglobin levels, diabetic retinopathy, and other prespecified factors. Data on smoking, diet, and supplement use were limited and could not be fully accounted for.
Implications Highlight Treatment Gap in AMD Care
Age-related macular degeneration is a leading cause of irreversible vision loss in adults older than 60. While treatments such as anti-vascular endothelial growth factor injections can slow advanced wet AMD, no approved therapies exist to prevent progression in earlier stages.
“Identifying a safe, low-cost drug that could delay disease progression would be a major advance,” said Dr. James Holloway, an ophthalmologist at University College London who was not involved in the study.
In adjusted analyses, metformin users showed odds ratios between 0.63 and 0.66 for developing intermediate AMD, with p-values ranging from 0.01 to 0.02. No significant association was found with early AMD.
An apparent reduction in late-stage AMD seen in unadjusted results disappeared after adjusting for age and sex, likely reflecting the small number of advanced cases.
Researchers cautioned that people not prescribed metformin tended to be older and had higher rates of AMD at baseline, raising the possibility of residual confounding.
The authors emphasized that the observational design limits conclusions about cause and effect. They also cited missing data on medication dose, adherence, and lifestyle factors, as well as the absence of optical coherence tomography imaging. Researchers noted that if confirmed by future trials, Metformin Use in Diabetes Patients could serve as a vital preventive therapy for AMD. This potential drug repurposing offers a promising new pathway for protecting vision specifically within the diabetic population.
Still, they said the findings support further investigation. “If confirmed in randomized trials, metformin could be repurposed as a preventive therapy for AMD, particularly among people with diabetes,” the study concluded.
