The influence of insulin on diabetic retinopathy and retinal vessel parameters in diabetes.

Aim: To investigate the associations between insulin use and diabetic retinopathy (DR), and retinal vascular parameters in type 2 diabetes (T2DM).

Methods: A total of 6,374 T2DM patients, consisting of 2,231 patients receiving insulin alone and 4143 patients without any hypoglycemic medication, were included in cross-sectional analyses. Among those without DR at baseline, 791 patients were followed for three years in longitudinal analyses. Fundus photography was taken to diagnose DR and calculate central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE), arteriolar-to-venular ratio (AVR), and vascular tortuosity. Inverse probability treatment-weighted analyses were performed.

Results: After adjusting for gender, age, body mass index, blood pressure, blood glucose, T2DM duration, smoking, and alcohol use, insulin users showed a higher risk of DR (odds ratio (OR) = 2.27, 95% confidence interval (95%CI) = 2.08-2.48, P < 0.001), larger CRVE (β = 3.92, 95%CI = 2.46-5.37, P < 0.001), smaller AVR (β=-0.0083, 95%CI=-0.0121- -0.0046, P < 0.001), and larger vascular curvature (β = 0.19, 95%CI = 0.05-0.33, P = 0.008). After 3 years, insulin users had a higher risk of developing DR (OR = 1.94; 95% CI = 1.37-2.73, P = 0.002), and greater change in CRVE (β = 3.92, 95%CI = 0.96-6.88, P = 0.009).

Conclusions: The impact of insulin on the retinal microvasculature provides support for linking insulin to the increased risk of DR, as well as cardiovascular events in T2DM.