title: Retinal vessel reaction in response to chromatic flickering light.
abstract: BACKGROUND
  Flickering light stimulation of the retina is known to increase retinal vessel diameter in animals and humans. The aim of the study was to quantify the response of retinal vessel diameter to red-green and blue-green flickering light.
  
  
  METHODS
  In 11 normal healthy volunteers (mean age: 25.2+/-6.8 years) retinal arterial and venous diameters were examined by Retinal Vessel Analyzer (IMEDOS Ltd., Weimar, Germany) before, during and after red-green and blue-green flicker stimulation with a frequency of 12 Hz and duration of 10 and 30 s.
  
  
  RESULTS
  For red-green flicker at 10 s there was a 2.4+/-1.4% arterial diameter increase at 9.1+/-3.3 s with a return to baseline after 30 s and a 2.4+/-1.1% venous diameter increase at 12.1+/-2.6 s with a return to baseline after 30 s. For red-green flicker at 30 s there was a 3.2+/-1.5% arterial diameter increase at 26.9+/-12.6 s with a return to baseline after 40 s and a 4.9+/-1.8% venous diameter increase at 31.4+/-7.6 s with a return to baseline after 40 s. For blue-green flicker at 10 s there was a 2.0+/-0.7% arterial diameter increase at 10.6+/-5.3 s with a return to baseline after 30 s and a 2.3+/-1.1% venous diameter increase at 12.0+/-5.5 s with a return to baseline after 30 s. For blue-green flicker at 30 s there was a 2.6+/-1.3% arterial diameter increase at 20.7+/-8.0 s with a return to baseline after 40 s and a 3.4+/-2.2% venous diameter increase at 28.8+/-10.5 s with a return to baseline after 40 s.
  
  
  CONCLUSIONS
  Retinal vessel diameter dilation is a reproducible response to the applied flicker stimuli. This finding supports the existence of neurovascular coupling in the human retina. Flicker stimulation in either red-green or blue-green might be a useful stimulus for examination of retinal vessel behavior to regulatory demands.
authors.affiliation: Augenklinik rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Germany. koskot2@gmx.net
authors.forename: Konstantin E
authors.initials: KE
authors.lastname: Kotliar
authors.forename: Walthard
authors.initials: W
authors.lastname: Vilser
authors.forename: Edgar
authors.initials: E
authors.lastname: Nagel
authors.forename: Ines M
authors.initials: IM
authors.lastname: Lanzl
mesh_terms: D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008027:Light; D008297:Male; D010775:Photic Stimulation; D012160:Retina / Q000528:radiation effects*; D012161:Retinal Artery / Q000502:physiology* / Q000528:radiation effects; D012169:Retinal Vein / Q000502:physiology* / Q000528:radiation effects