Metformin use linked to modest glaucoma risk reduction in diabetic patientsMetformin use linked to lower glaucoma risk in people with diabetes

American journal of ophthalmology Published June 1, 2026 Study authors: Abdelaal Abdelaziz, Abu Serhan Hashem, Alsaadi Mustafa, Abou Jabal Kamel, Rustam Zainab, Talaparthy … PubMed ↗ DOI ↗ Editorial oversight: Dr. Lars van Dijk, PhD · Surgical, Procedural & Diagnostic

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Key Takeaway

Metformin use in diabetic patients may modestly reduce glaucoma risk, but evidence certainty is low to moderate.

This systematic review and meta-analysis synthesized data from observational cohort studies involving over 1.2 million patients with diabetes to evaluate the association between metformin use and glaucoma incidence. The primary analysis of crude odds ratios showed no significant association (OR 0.96, 95% CI 0.87-1.06), suggesting that raw comparisons between metformin users and nonusers or users of other antidiabetic drugs did not indicate a clear effect. However, sensitivity analyses that excluded nonmetformin active comparators revealed a modest but statistically significant reduction in glaucoma risk (OR 0.92, 95% CI 0.87-0.98), hinting at a potential protective effect when more specific comparisons are made.

Time-to-event analyses provided further insight, with unadjusted hazard ratios showing a lower risk among metformin users (HR 0.86, 95% CI 0.79-0.93). After adjustment for confounders, the association remained significant but attenuated (aHR 0.88, 95% CI 0.80-0.96), indicating that metformin use may be independently associated with a reduced glaucoma risk in diabetic populations. These findings are consistent across different analytical approaches, though the magnitude of the effect is modest.

The certainty of evidence ranged from very low for comparator analyses to moderate for time-to-event analyses, reflecting limitations such as high heterogeneity (I² = 79.14% for crude OR analysis) and the observational nature of the studies. Safety data were not reported, and follow-up duration was unspecified, which constrains the ability to draw definitive causal inferences. Nonetheless, the practice relevance is notable, as identifying systemic medications that could modify glaucoma risk may inform prevention strategies for diabetic patients.

Key limitations include the reliance on observational data, which are prone to confounding and selection bias, and the high heterogeneity across studies. The authors caution against overinterpreting crude analyses, which showed no association, while sensitivity and time-to-event analyses suggested a possible protective effect. Funding and conflicts of interest were not reported, which may introduce additional bias.

In clinical practice, these results suggest that metformin use in diabetic patients might be associated with a modest reduction in glaucoma risk, but the evidence is not strong enough to recommend metformin specifically for glaucoma prevention. Further research, ideally through randomized controlled trials, is needed to confirm these associations and explore underlying mechanisms.

Overall, this meta-analysis highlights a potential link between metformin and reduced glaucoma incidence in diabetic patients, but the findings should be interpreted with caution due to the observational design and varying evidence certainty. Clinicians should consider these results as hypothesis-generating rather than definitive guidance for treatment decisions.

People with diabetes face many health challenges, and one of the most common is glaucoma. This eye condition can lead to vision loss if not caught early. For years, doctors have wondered if the daily diabetes pill metformin could help protect the eyes. A new analysis of over 1.2 million patients looks at this question. The goal was to see if taking metformin changes the risk of getting glaucoma compared to not taking it or taking other diabetes medicines.

The researchers looked at data from many different studies. They included 732,423 people who took metformin and 513,292 people who did not. These groups were compared to see who developed glaucoma over time. The studies were observational, meaning they watched what happened in real life rather than assigning the drug in a controlled experiment. This approach helps understand how people actually use medicine in their daily routines.

When looking at the raw numbers, the study found no clear link between metformin and glaucoma risk. However, when the team adjusted the math to account for other factors, the picture changed. The analysis showed that metformin users had a lower risk of developing glaucoma. Specifically, the risk was about 12% lower in the adjusted analysis. Another look at the data, which excluded other active drugs for comparison, also showed a modest but significant drop in risk. This suggests metformin might offer some eye protection.

Safety was a key part of this review. The researchers did not report specific side effects or reasons people stopped taking the drug in this analysis. Because the data came from existing records, detailed safety reports were not included. This means we do not know exactly how many people stopped the drug due to issues, but the overall focus was on the disease risk.

It is important to be careful with these findings. The certainty of the evidence ranged from very low to moderate. This is because the studies were observational, which means they can show a link but cannot prove the drug caused the protection. Other factors like diet or exercise might also play a role. People should not stop or start any medication based on this single study. Always talk to your doctor about your specific health needs.

For patients with diabetes, this research offers a new perspective. Identifying medicines that might lower glaucoma risk could help with prevention strategies. If metformin does offer protection, it adds another reason to take this common drug as prescribed. It is a small piece of the puzzle, but it could help keep vision safe for millions of people.

What this means for you:

Analysis of over 1.2 million patients suggests metformin may modestly lower glaucoma risk in people with diabetes.

Study Details

Study typeMeta analysis

Sample sizen = 1,247,325

EvidenceLevel 1

PublishedJun 2026

PMID41812849

View Original Abstract ↓

TOPIC: To evaluate whether metformin use is associated with a reduced risk of developing glaucoma. CLINICAL RELEVANCE: Glaucoma is a leading cause of irreversible blindness worldwide. Identifying systemic medications that may modify glaucoma risk could have important implications for prevention strategies in patients with diabetes, a population frequently treated with metformin. METHODS: This systematic review and meta-analysis of observational cohort studies, registered on PROSPERO (CRD420250655975), was done through PubMed, Scopus, Web of Science, and Google Scholar until June 16, 2025. Eligible studies compared glaucoma incidence among metformin users versus nonusers or users of other antidiabetic drugs (ADDs). Risk of bias was assessed using the Newcastle-Ottawa Scale. Binary outcomes were pooled using random-effects models to calculate odds ratios (ORs), and time-to-event outcomes were synthesized using hazard ratios (HRs). Subgroup analyses explored confounder adjustment methods and comparator types. Certainty of evidence was graded using GRADE framework. RESULTS: Twelve retrospective cohort studies (n = 1,247,325; 732,423 metformin users; 513,292 controls) were included. The pooled crude OR showed no association between metformin use and glaucoma risk (OR = 0.96; 95% CI, 0.87-1.06; I² = 79.14%; low certainty). A leave-one-out sensitivity analysis excluding a study with a nonmetformin active comparator resulted in a modest but significant reduction in risk (OR = 0.92; 95% CI, 0.87-0.98; low to moderate certainty). No effect modification was detected by the confounder adjustment method (propensity-score matched vs regression; P = .20; low certainty) or comparator type (no metformin vs other ADDs; P = .34; very low certainty). The follow-up duration did not significantly modify the effects. Four studies contributed time-to-event analyses: pooled unadjusted HR indicated a lower risk among metformin users (HR = 0.86; 95% CI, 0.79-0.93; I² = 0%; moderate certainty), which persisted in adjusted models (aHR = 0.88; 95% CI, 0.80-0.96; I² = 0.01%; moderate certainty). There was no evidence of small-study effects (Egger's P = .955). CONCLUSION: Across observational cohorts, metformin use was not associated with a reduced glaucoma risk in crude analyses; however, sensitivity analyses suggested a possible protective effect. Time-to-event analyses consistently demonstrated a modest reduction in glaucoma risk, supported by moderate-certainty evidence after adjusting for confounders. Overall, certainty of evidence ranged from very low (comparator analyses) to moderate (time-to-event analyses).

Metformin use linked to modest glaucoma risk reduction in diabetic patientsMetformin use linked to lower glaucoma risk in people with diabetes

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