CHOROIDAL BLOOD FLOW IN LIGHT AND DARK ADAPTATION

Title CHOROIDAL BLOOD FLOW IN LIGHT AND DARK ADAPTATION
Author, Co-Author John Lovasik O.D., Helene Kergoat, Pierre Jeanson
Topic
Year
1992
Day
Monday
Program Number
Poster 25
Room
Great Hall
Affiliation
Abstract The retina is nourished by the choroidal and retinal vasculature. In lower vertebrates the photoreceptor (PR)- retinal pigment epithelium (RPE) complex markedly increases its O2 consumption in the dark because of increased Na transport (Zuckerman & Weiter, 1980). Feke et al. (1983) found a 40% to 70% increase in retinal blood flow in man after transition from light to dark. This was hypothesized to reflect a feedback autoregulatory response in retinal vessels which compensates for any decreased O2[subscript] transfer from the choroid towards the inner retina. In the present study, we tested the hypothesis that the reported increase in O2 consumption in the PR-RPE complex during dark adaptation (DA) is supported by a gradual increase in the choroidal pulsatile ocular blood flow (POBF) in parallel with the increasing sensitivity of rods. Each of nine healthy volunteers (20-43 yrs) had their POBF measured every 2 min. with a Langham Ocular Blood Flow System during 16 min light, 32 min dark, 16 min light adaptation periods. POBF measurements in the dark phase were taken under dim yellow light displayed for some 15 sec. Scotopic blue flash electroretinograms verified that this light had only a very minor effect on DA. The POBF varied within and across test conditions and subjects. No differences were found for, 1) the group averaged slopes of regression lines through each data set (ANOVAs, p=0.8182) or their Y intercepts (ANOVAs, p=0.7516), 2) POBF values collapsed over time for each light condition and all subjects (ANOVAs, p=0.2712), 3) POBF values combined across all subjects and test conditions (ANOVAs, p=0.5236). Within the limitations of the systems and procedures employed, we conclude that DA is not associated with increased choroidal POBF. The theoretical and practical implications of these data are discussed.
Affiliation of Co-Authors
Outline