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Response of parapapillary retinal vessels to exercise
1Ecole d'Optométrie, Université de Montréal, Québec, Canada.
Purpose:
Using blue field entoptoscopy, we have recently shown that blood flow in the paramacular capillaries remained constant after moderate exercise. In the present study, our objective was to identify a mechanism by which perfusion of an area populated by capillaries of invariable diameter can be maintained constant during exercise, which changes blood flow throughout the body.
Methods:
Twelve healthy volunteers between 20 and 30 years of age participated in the present study. Color fundus slides centered on vessels within 1 disc diameter of the optic nerve head and synchronized with systole or diastole were taken while subjects rested, and after 20 min of stationary bicycling. High resolution measurements of vessel diameter were based on density plot profiles generated from magnified and digitized images of neighboring arteries and veins.
Results:
Our results showed that the group-averaged diameter of arteries measured either in systole or diastole decreased after exercise, but the group-averaged diameter of veins did not differ from baseline.
Conclusions:
We interpret the constriction of parent arteries as an effective mechanism for gating the flow of blood to downstream vessels such as those perfusing the macular area.