Abstract
Purpose: :
To investigate the relationship between retinal circulation and duration of type 2 diabetes mellitus.
Methods: :
Using a laser Doppler velocimetry system (CLBF Model 100; Canon, Tokyo, Japan), we measured retinal vessel diameter and blood velocity and calculated retinal blood flow (RBF), pulsatility ratio, and resistive index in the retinal arterioles in 194 eyes of 194 patients (102 men, 92 women; mean age±SD, 59.8±10.3 years). Patients with type 2 diabetes had no diabetic retinopathy (n=143) or background diabetic retinopathy (n=51). To examine whether diabetes-related changes in RBF are associated with the duration of diabetes, we divided patients into the four groups based on the disease duration (group A, 15 years, n=45).
Results: :
There were no differences in retinal arteriolar vessel diameter among the four groups. However, there were significant differences in blood velocity, RBF, pulsatility ratio, and resistive index. The average blood velocity in group A was significantly lower than in group C. RBF significantly increased in groups B and C compared with group A, whereas there was no difference in RBF between groups A and D. The pulsatility ratio and resistive index significantly increased in group D compared with group A.
Conclusions: :
RBF may decrease in early-phase diabetes and may tend to increase with the increased duration of type 2 diabetes. However, the RBF decreased but the pulsatility ratio and resistive index increased in patients who have the disease longer than 15 years, suggesting that increased vascular rigidity may be involved with decreased RBF in long-duration type 2 diabetes.
Keywords: diabetic retinopathy • blood supply • diabetes