A large retrospective cohort study using data from over 723,000 Taiwanese patients with newly diagnosed diabetes mellitus found that lower cumulative doses of metformin were associated with a modestly reduced risk of developing open-angle glaucoma. However, higher doses showed no protective effect. The findings suggest comorbidities such as myopia, cataract and hyperthyroidism may play a more significant role in OAG risk than metformin use alone.

A new study published in the Journal of Glaucoma suggested that lower dosages of Metformin may have a protective effect on OAG risk, but higher doses had no significant impact.

“The underlying mechanisms linking cumulative metformin dosage to OAG risk are not yet fully understood, highlighting the need for future prospective clinical trials to assess the potential benefits and risks of metformin treatment for OAG in DM patients,” they concluded in their paper. “Our analysis highlights that comorbidities such as hyperthyroidism, myopia and cataract play a more substantial role in elevating OAG risk compared to DM itself or metformin use. These findings underscore the importance of considering coexisting conditions in the management of OAG risk among DM patients, suggesting that the influence of metformin may be secondary to these underlying factors.”

Huang SW Lai YR, Yang Y, Gau SY, Chung NJ, Tsai TH, Huang KH, Lee CY. Association between long-term metformin use and risk of open-angle glaucoma in patients with diabetes mellitus. Journal of Glaucoma. May 16, 2025.