title: Retinal arteriolar dilation to flicker light is reduced on short-term retesting.
abstract: OBJECTIVE
  To investigate the impact of retesting frequency over a short period on flicker light-induced retinal vasodilation.
  
  
  METHODS
  Twenty healthy participants were included. The retinal vascular response to flicker light stimulation was assessed three times (at baseline and after 5 and 30 minutes of rest [tests 1, 2, and 3, respectively]) in each participant using the Dynamic Vessel Analyzer. Relative dilations of selected arteriole and venule segments during flicker stimulation and resting diameters were measured automatically. The mean vessel dilations and resting diameters were compared using repeated-measures analysis of variance.
  
  
  RESULTS
  Participants were young (mean [SD] age, 33.1 [5.7] years) and mostly female (70%). The mean (SD) maximum arteriolar dilations during flicker stimulation were 3.23% (2.06%), 2.44% (1.62%), and 3.36% (2.11%) in tests 1, 2, and 3, respectively. The mean (SD) venular dilations were 4.26% (1.28%), 3.81% (1.61%), and 4.43% (1.73%) in tests 1, 2, and 3, respectively. The mean arteriolar dilations were significantly different across the three tests (P < 0.001). Compared with test 1, arteriolar dilations were significantly reduced after 5 minutes (P = 0.008) but not 30 minutes (P = 0.437) of rest. No significant differences were found over time for the mean venular dilations (P = 0.128). Resting diameters of selected vessels were not significantly different between tests.
  
  
  CONCLUSIONS
  Retinal arteriolar dilation during flicker stimulation is reduced on short-term retesting, without a significant change in baseline vessel diameter, indicating decreased responsiveness to the flicker stimulus. Researchers should allow at least 30 minutes between consecutive tests to minimize suppression of the flicker response.
authors.affiliation: Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Noonan
authors.forename: Thanh T
authors.initials: TT
authors.lastname: Nguyen
authors.forename: Ryan E K
authors.initials: RE
authors.lastname: Man
authors.forename: William J
authors.initials: WJ
authors.lastname: Best
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
authors.forename: Ecosse L
authors.initials: EL
authors.lastname: Lamoureux
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D010775:Photic Stimulation; D012171:Retinal Vessels / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*; D055815:Young Adult
keywords: diabetes; flicker light; functional hyperemia; neurovascular coupling; retinal circuitry