Submitted on November 30, 2004
Accepted on March 25, 2005
Blue flicker modifies the subfoveal choroidal blood flow in the human eye
John V Lovasik1*, Helene Kergoat1, and Marcelo A Wajszilber1
1 School of Optometry, University of Montreal, Montreal, Quebec, Canada
* To whom correspondence should be addressed. E-mail: john.vincent.lovasik{at}umontreal.ca.
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 is already demonstrated for retinal blood flow, but rejected for the 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 1Hz and 64Hz was first increased, then decreased by 4.0 log units in 1.0 log unit steps between 0.0375 cd/m2 and 375 cd/m2. In separate testing, flash electroretinograms (ERGs) provided electrophysiological indices of the relative response of shortwave cones and rods to blue light stimulation. Group-averaged, normalized ChBF measurements revealed that it was modulated by ~9% by flicker frequency. Increasing the blue flicker luminance from low-to-high attenuated the subfoveal choroidal flow, volume (ChBVol), and velocity (ChBVel) by ~32%, ~30%, and ~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 shortwave cone-dominated retinal responses. Collectively, these findings indicate that 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.
