Effects of habitual cigarette smoking on retinal circulation in patients with type 2 diabetes

Abstract

PURPOSE. To examine the long-term effects of cigarette smoking on retinal circulation in patients with type 2 diabetes. METHODS. Seventy-four patients with type 2 diabetes mellitus and minimal (no or mild nonproliferative) diabetic retinopathy (DR) were evaluated. These patients with type 2 diabetes were divided into three groups based on their smoking history: current smokers (n = 19), past smokers (n = 20), and never smoked (n = 35). The retinal circulatory parameters were measured with laser Doppler velocimetry and were compared among the groups. RESULTS. There were significant decreases in the retinal blood flow (RBF; 8.9 ± 2.9 vs. 11.6 ± 3.1 μL/min, P = 0.009) with decreased blood velocity (V; 29.6 ± 6.8 vs. 37.8 ± 9.0 mm/s, P = 0.003) but no difference in the vessel diameter (D; 112.0 ± 11.9 vs. 113.7 ± 8.6 μm, P = 0.57) in the current smokers compared with those who never smoked. There were no differences in the RBF, blood V, and vessel D in the past smokers compared with those who never smoked and current smokers. Multiple regression analysis showed that the creatinine level was correlated negatively with the RBF and that current smoking was significantly and independent correlated with decreased RBF. CONCLUSIONS. Our results indicated that the blood V and RBF in the retinal arterioles may decrease in patients with type 2 diabetes who are chronic smokers, suggesting that chronic smoking may be associated with decreased RBF, probably via lower blood V in the retinal arterioles in early-phase DR.