Abstract
Purpose :
Recent studies support the use of metformin to prevent the development of age-related macular degeneration (AMD). However, the mechanism by which metformin is protective is unclear. We performed a retrospective, cross-sectional clinical study to assess the association between metformin use and AMD when controlling for glycemic control in patients with diabetes mellitus type II.
Methods :
We identified 461 unique patients over the age of 55 years with a diagnosis of diabetes mellitus type II seen in our academic retina clinic in Stony Brook, New York between 12/31/2019 and 12/31/2020. Manual chart review was performed to extract the most recent A1c within 3 months and the presence of an active metformin prescription. The population was split based on presence of AMD diagnosis. A series of multivariate regression analyses was then performed comparing metformin use between groups while controlling for A1c. Secondary endpoints included demographic differences, smoking status, and prevalence of diabetic retinopathy (DR) between groups.
Results :
Among the 461 patients, 118 (25.6%) had a diagnosis of AMD. Compared to patients without AMD, patients with AMD were older (69 compared to 66; p=0.005) and less likely to have DR (37.3% compared to 59.2%; p<0.001). There was no difference in use of metformin and average A1c between groups. After multivariate regression, variables found to be associated with AMD include age (OR 1.05; p=0.001) and DR (OR 0.35; p<0.001). Metformin use was not found to be associated with AMD and controlling for A1c did not change the association. Stratifying glycemic control using various A1c cutoffs also showed no changes in the relationship between AMD and metformin use.
Conclusions :
This is the first reported study assessing the relationship between AMD and metformin use while controlling for glycemic control using A1c. Given our results, the previously described relationship between metformin use and the development of AMD is not likely driven by the antihyperglycemic effects of metformin, but rather by other properties inherent to the drug. Lastly, the use of DR as a surrogate for poor diabetic control in the context of AMD is not ideal, as we found DR to be significantly associated with AMD even after holding A1c constant.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.