Correlation of Vessel Diameters, Their Response to Flicker Light, and Oxygen Saturation in Diabetic Patients

Abstract

Purpose: : In diabetic patients, hyperglycaemia results in micro-angiopathy provoking disturbances of blood flow and oxygen supply. This study was conducted in order to find out relationships between different measures describing retinal micro-angiopathy.

Methods: : 160 diabetic patient with no or non-proliferative retinopathy were included in this study. Retinal vessel diameters (central retinal arterial and venous equivalents - CRAE and CRVE as well their ratio - AVR), the vessel diameter response secondary to flicker light stimulation as well as the vessel oxygen saturation (SO2) were measured using the Retinal Vessel Analyser.

Results: : A strong correlation of the arteriolelar and venular dilation secondary to flicker light stimulation was found (p<0.0005). The venous vasodilatation was negatively correlated with the vessel diameter (CRVE). Vessel diameters (CRAE as well as CRVE) correlated positively with the venous SO2 (p=0.047 and p=0.026) and negatively with the arterio-venous SO2-difference (p=0.002 and p=0,035). Furthermore, a negative correlation of the arterial SO2 was found with the AVR (p=0.047).

Conclusions: : Arterial as well as venous dilation under flicker light stimulation is mediated by a common pathway, probably NO. While the arterial dilation, despite reduced in early stages of diabetic retinopathy compared to that of healthy subjects, is independent from the baseline vessel diameter, the venous dilation reduces with increasing vessel diameter. Together with an increasing CRVE with increasing severity of the retinopathy, this indicates venous dilation by diabetic conditions which reduce the capacity of further dilation by the flicker. Increased venous oxygen saturation is an indicator of insufficient oxygen supply to the retina. The correlation of the vessel diameters with venous SO2 may point to compensatory mechanisms of retinal blood flow regulation. Combining measurements of vessel diameters, their response to flicker, and oxygen saturation may give deeper insight in blood flow and oxygen supply regulation in the diabetic retina.

Keywords: diabetic retinopathy • blood supply • oxygen