Abstract
Abstract: :
Purpose: to test the hypothesis that the position of the dicrotic notch on the blood velocity waveform may indicate the alteration of vascular tone in retinal circulation of diabetic subjects.Methods: Retinal blood flow was measured in the superior–temporal arteriole approximately 1 disc diameter from the optic nerve head with the Canon Laser Blood Flowmeter. Blood velocity waveforms were analyzed in regard to the vertical position of the dicrotic notch (N) relative to peak systolic (S) and minimum diastolic velocities (D). Two ratios R1=N/S and R2=(N–D)/(S–D) were calculated. Results: 10 diabetic subjects with moderate NPDR and ME (mean age 57,6 years, mean duration of diabetes 10,8 years)and 10 healthy subjects (mean age 55,4 years) were recruited. In the diabetic group mean R1 was 0.61 and mean R2 was 0.47; in control group R1 and R2 were 0.7 and 0.57 respectively. The difference between the two groups for R1 and R2 was statistically significant (p<0.01 & p<0.01, respectively), irrespective of an identified influence of heart rate. Conclusions:The position of the dicrotic notch on the arteriolar blood velocity waveform is displaced downwards in type 2 diabetic subjects with moderate NPDR and ME, when compared to healthy, age–matched controls. This displacement at least partially depends on the heart rate, but may also reflect the vascular tone alteration in diabetic subjects. The expansion of the study groups will help to validate these preliminary findings.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • diabetic retinopathy • clinical (human) or epidemiologic studies: natural history