Metformin plus insulin therapy reduces HbA1c and improves retinal microvascular density in type 2 diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of blindness in patients with type 2 diabetes mellitus (T2DM), characterized by progressive damage to retinal microvessels. While glycated hemoglobin (HbA1c) reflects long-term glycemic control, and optical coherence tomography (OCT) offers detailed retinal microvascular assessment, the specific effects of different hypoglycemic regimens, particularly metformin and insulin, on these microvascular changes and DR progression remain underexplored. Understanding these impacts is crucial for optimizing treatment strategies to preserve vision.

This retrospective study analyzed 93 T2DM patients with non-proliferative DR, matched by propensity score into three groups of 31 patients each: metformin monotherapy (M), insulin-based therapy (Ins), or combined metformin-insulin therapy (M-Ins). Patients were followed for 2 years, with HbA1c, HbA1c variability (HbA1c-SD), DR grade, central macular thickness (CMT), retinal nerve fiber layer (RNFL) thickness, and superficial/deep capillary plexus (SCP/DCP) density recorded at baseline, 1-year, and 2-year follow-ups. Multiple linear and Cox regression analyses were used to assess relationships and risk factors.