Abstract
Purpose: :
The Retinal Function Imager (RFI) implements a new, non-invasive diagnostic approach to measuring blood flow velocity, revealing vascular network structure, and obtaining information about the oximetric and metabolic status of the retina. Here we compared the blood flow velocity of diabetic patients to that of healthy controls.
Methods: :
Thirty seven eyes of 27 patients with non-proliferative diabetic retinopathy (NPDR) and 24 eyes of 16 subjects were enrolled. All patients were scanned by RFI with quantitative analysis of blood flow velocity of secondary and tertiary branches of arteries and veins. Vessel segments were subdivided into 3 categories by width: smaller than 10µ, between 10µ and 20µ, and wider than 20µ. Differences among groups were assessed by mixed model effect.
Results: :
There was no statistically significant difference between the average age, sex and mean arterial pressure in the diabetes and the healthy group. The heart rate in the diabetic eyes was higher than in the healthy group (79.2 ± 11.6, 69.4 ± 6.4 beats/min respectively, p<0.0001). The average velocity in arteries of diabetic patients was 3.66 ± 1.21 mm/second; in the healthy group it was 3.98 ± 0.78 mm/second. The differences were significant when including heart rate as a covariant in the analysis of the velocity (p=0.027). The average venous velocity was lower than the arterial velocity in both groups. It was 2.56 ± 0.63 mm/second in the diabetic group and 2.63 ± 0.50 mm/second in the healthy one, the difference was not significant even after adding heart rate as a covariant. The arteries width category where velocity was mostly attenuated in the diabetic patients was 10-20 µ (3.49 ± 1.16 mm/second in diabetes, 3.95 ± 0.79 mm/second in healthy, p=0.003). We did not find difference in velocity between subgroups of diabetic patients who had or hadn’t macular edema or prior macular laser treatment.
Conclusions: :
The RFI detected decreased blood flow velocity in retinal arteries and of diabetic patients. The reduced velocity was observed mainly in arteries 10 to 20 µ width. These findings support the notion that abnormalities in vessel function exist in diabetic retinopathy eyes. The RFI provides a non-invasive technique to assess haemodynamic abnormalities in diabetic retinopathy.
Keywords: diabetic retinopathy • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • blood supply