title: Blue flicker modifies the subfoveal choroidal blood flow in the human eye.
abstract: The objective of the present study was to reveal an interaction between choroidal blood flow (ChBF) and light-induced photoreceptor activity, a physiological coupling that has been already demonstrated for retinal blood flow but rejected for ChBF. Ten healthy adults volunteered for this study. A real-time recording near-infrared laser-Doppler flowmeter was used to quantify the subfoveal ChBF while the luminance of blue flicker between 1 and 64 Hz was first increased and then decreased by 4.0 log units in 1.0-log unit steps between 0.0375 and 375 cd/m2. In separate testing, flash electroretinograms (ERGs) provided electrophysiological indexes of the relative response of short-wave cones (s-cones) and rods to blue light stimulation. Group-averaged, normalized ChBF measurements revealed that it was modulated by approximately 9% by flicker frequency. Increasing the blue flicker luminance from low to high attenuated the subfoveal ChBF, volume, and velocity by approximately 32%, approximately 30%, and approximately 5%, respectively. Decreasing the luminance from high to low over the same range had no effect on the subfoveal choroidal hemodynamics. The markedly different effects of reversed directions of change in blue flicker luminance on the subfoveal ChBF were linked to transitions between rod-dominated and s-cone-dominated retinal responses. Collectively, these findings indicate that the blue light-induced photoreceptor response is associated with a differential distribution of the ChBF across the ocular fundus according to the degree and type of retinal photoreceptor stimulated.
authors.affiliation: Ecole d'Optométrie, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, Québec, Canada H3C 3J7. john.vincent.lovasik@umontreal.ca
authors.forename: John V
authors.initials: JV
authors.lastname: Lovasik
authors.forename: Hélène
authors.initials: H
authors.lastname: Kergoat
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Wajszilber
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000528:radiation effects; D001810:Blood Volume / Q000528:radiation effects; D002829:Choroid / Q000098:blood supply*; D003116:Color; D003199:Computer Systems; D004596:Electroretinography / Q000379:methods; D005260:Female; D005584:Fovea Centralis; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008027:Light; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D012039:Regional Blood Flow / Q000528:radiation effects; D012160:Retina / Q000502:physiology; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors