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Christina Ryu, Metasebia Munie, Salma Noorulla, Paul Edwards, Xiaoxi Qiao, Hua Gao; Effect of Metformin on the Development of Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2449.
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Metformin is a widely used oral anti-hyperglycemic agent for type 2 diabetics. In vitro studies indicate that metformin inhibits proliferation and migration of vascular endothelium, and it has anti-angiogenic effects in cancer models in vivo. Metformin therefore may theoretically protect against the microvascular complications of diabetes. This study investigates whether the risk of development of proliferative diabetic retinopathy is reduced in type 2 diabetic patients treated with metformin.
This is a retrospective study of patients with longstanding type 2 diabetes. Patient charts were reviewed from January 1990 to November 2012. Patients with type 2 diabetes for more than 20 years were included. Patients without ophthalmology record, primary care record or hemoglobin A1C levels were excluded. The primary outcome was to compare the rates of severe diabetic retinopathy in patients on metformin with those not on metformin.
78 patients with diabetic retinopathy are included in our current analysis, 45 patients on metformin and 33 patients not on metformin. Our data show that patients on metformin were less frequently treated with insulin (p = 0.004). In the non-metformin group, 18 (54.5%) patients developed nonproliferative diabetic retinopathy (NPDR) and 15 (45.5%) developed proliferative diabetic retinopathy (PDR). In the metformin group, 32 (72.7%) developed NPDR and 12 (27.3%) developed PDR. Thus our data shows a trend of much less PDR in the metformin group than the non-metformin group.
Although other confounding factors may contribute to the severity of diabetic retinopathy, our study shows that metformin may reduce the rate of development of proliferative diabetic retinopathy. A larger scale study with more patients is required to confirm our findings.
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