Flicker Response of Retinal Vessels in Type-1 Diabetics

Abstract

Purpose: : To compare vessel diameter changes in response to flickering in type 1 diabetics and in a group of healthy volunteers. It was investigated how retinal flicker response is influenced by the factors insulin pump treatment, age, duration of diabetes, HbA1c, blood pressure, intraocular pressure and current blood glucose level.

Methods: : Thirty-two type-1 diabetics with no ophthalmoscopic sign of diabetic retinopathy and fifteen healthy volunteers were examined using the IMEDOS Retinal Vessel Analyzer. In addition to dynamic vessel analysis to determine flicker response, the arterio-venous ratio of the retinal vessels, blood glucose levels, intraocular and blood pressure were measured.

Results: : Arterial and venous vessel dilations induced by flickering light were observed to be significantly diminished in the group of type-1 diabetics when compared to flicker response in healthy volunteers (maximum arterial dilation 1.63±2.23% in diabetics and 4.33±1.53% in healthy volunteers; maximum venous dilation 2.66±1.66% in type-1 diabetics and 4.90±2.15% in healthy volunteers; p values < 0.001). Duration of diabetes showed a significant inverse correlation to flicker response of retinal vessels, whereas the factors age, HbA1c, blood glucose level, blood and intraocular pressure were not significantly correlated to the extent of vessel reaction. Of the thirty-two examined type-1 diabetics, seventeen patients whose treatment regimen includes use of an insulin pump were observed to have significantly better arterial and venous reactions than those who use insulin injections, with maximum dilations being 2.83±2.70% vs. 0.57±0.83% for the arterial, and 3.37±1.50% vs. 2.04±1.58% for the venous reaction (p values 0.003 and 0.020, respectively). All values are given as mean±sd.

Conclusions: : A significant decrease in retinal flicker response, consistent with the finding of endothelial dysregulation and impairment of retinal blood flow even before appearance of clinically detectable retinopathy, was observed in type-1 diabetics. Flicker response was observed to be more drastically reduced in patients with insulin injection therapy than in patients with insulin pump treatment and significantly decreased with longer duration of diabetes.

Keywords: diabetes • diabetic retinopathy • retina