Association between metformin use with circumpapillary retinal nerve fibre layer thickness and capillary vessel density in glaucoma.

Background/aims: To investigate the association between use of metformin and circumpapillary retinal nerve fibre layer (cpRNFL) thickness, as well as whole image capillary density (wiCD), in patients with glaucoma.

Methods: This cross-sectional study included patients with glaucoma suspect or primary open-angle glaucoma (POAG) underwent optical coherence tomography angiography imaging. Use and duration of antidiabetic medications were assessed at the time of imaging. Multivariable linear mixed-effect modelling was used to estimate the effect of diabetes medication on wiCD and cpRNFL while controlling for covariates including age, race, body mass index, diagnosis, 24-2 visual field mean deviation, and intraocular pressure, average signal strength index as well as any variables that showed a p <0.1 in the univariable analysis.

Results: A total of 577 eyes (330 POAG and 247 glaucoma suspect) of 346 patients were included. Sixty-five patients (23%) had diabetes, of whom 55 (78.5%) used metformin, and 17 (26.2%) used insulin. After adjusting for covariates, the association between metformin use and wiCD (1.56 (95% CI 0.40 to 2.71); p=0.008), duration of metformin use and wiCD (0.12 (95% CI 0.02 to 0.22) per 1 year longer; p=0.037), and metformin use and cpRNFL thickness (5.17 (95% CI 1.24 to 9.10) µm; p=0.010) had statistically significant associations in each model.

Conclusions: Metformin use was associated with higher wiCD and thicker cpRNFL. These findings indicate a potential association, underscoring the need for longitudinal studies to determine if metformin plays a role in the retinal conditions of patients with glaucoma.

Trial registration number: NCT00221897.