Retinal vessel reaction to 100% O2-breathing--functional imaging using the retinal vessel analyzer with 10 volunteers

Abstract

Retinal vessel diameter assessment is complicated by various components among them dynamic changes due to vasomotoric effects. Measurement of these diameters was usually obtained from fundus photographs. Functional diameter changes induced by external stimuli were difficult to evaluate because of their dynamic nature. The Retinal Vessel Analyzer (RVA) allows continuous on-line measurement of those dynamic changes. Whether functional changes due to 100% O2 breathing can be assessed by RVA is investigated in this study. Continuous on-line registration of retinal arterial and venous branch vessels was obtained in 10 healthy volunteers. A baseline was taken during the first minute. Then for 5 minutes 100% O2 was delivered by mask. Further recording ensued for 4 minutes, while breathing room air. Vessel diameter change in percent to baseline was calculated for each individual and for a mean of the group. Each individual demonstrated vasoconstriction. The mean diameter reduction for the group was 6.5% for arteries and 15% for veins. RVA allows assessment of functional retinal branch vessel reactions. Retinal branch vessels diameters are denominators for capillary perfusion. RVA might be able to demonstrate an individual vessel's regulation potential by purposeful stimulation to constrict and dilate. This property could be helpful in understanding pathophysiologic processes as well as improving diagnosis and therapeutic effects in diseases influencing ocular perfusion such as diabetes, retinal vessel occlusion or even glaucoma. Further evaluation of effects of systemic diseases might be an additional application of functional retinal vessel diameter assessment by RVA.