title: Response of parapapillary retinal vessels to exercise.
abstract: OBJECTIVE
  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.
authors.affiliation: Ecole d'Optométrie, Université de Montréal, Québec, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Kergoat
authors.forename: J V
authors.initials: JV
authors.lastname: Lovaski
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure; D015444:Exercise / Q000502:physiology*; D005654:Fundus Oculi; D006339:Heart Rate; D006706:Homeostasis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009898:Optic Disk / Q000098:blood supply*; D010781:Photography; D012039:Regional Blood Flow / Q000502:physiology; D012171:Retinal Vessels / Q000502:physiology*