Abstract
Purpose: :
Exposure of the retina to flickering light induces retinal vessel dilation in healthy subjects. The effect is termed neurovascular coupling. Vessel responses are assumed to be different in various diseases. Diabetes mellitus and related vascular disorders are able to change vascular endothelial function. Whether the dynamic reaction to luminance flicker stimulation in retinal branch arteries and veins differs between healthy volunteers and patients suffering from diabetes type 1 is investigated.
Methods: :
Retinal vessel reactions to flicker stimulation were examined in 35 patients with insulin dependent diabetes mellitus type 1 (age (mean±SD) 50,9±8,6 years old) and in 35 age and gender matched medically healthy volunteers. Vessel diameters of retinal vessel segments were assessed by Dynamic Vessel Analyzer (DVA). After baseline measurement (50 s) monochromatic rectangular flicker stimulation (530-600 nm, 12,5 Hz, 20 s) was applied 3 consecutive times. Statistical data analysis of the measured parameters independent from the commercial DVA program was performed.
Results: :
In most subjects fast vessel dilation compared to baseline and an ensuing reactive arterial constriction were observed. In detail we found:………………………………. .diabetes…...controlmean maximal arterialdilation, [%]……………………2,3±1,8**.....4,1±2,2time of max. arterial dilationduring the stimulation, [s]...19,3±10,9*....14,2±3,4mean maximal venousdilation, [%]………………...…3,4±1,8*.......4,7±1,8There were statistically significant differences between the two examined groups as marked with *(p<0,05), **(p<0,005) (T-test).
Conclusions: :
Functional retinal arterial and venous reaction to flicker stimulation differs high significantly between diabetes type 1 patients and healthy subjects of the same age and gender. Maximal dilation as a response to the stimulus is not reached. These findings might be an indication for alterations in the vascular endothelium and vessel wall rigidity in diabetes, leading to impaired regulation following metabolic demand.
Keywords: diabetes • blood supply • retina