Retinal blood flow in the cat following periods of light and darkness

Estimates of flow velocity in retinal arterioles of seven cat eyes were obtained using high-speed cine Indocyanine Green absorption angiography in the near-infra-red waveband, following alternate 30 min periods of light and darkness. Simultaneous estimates of vessel calibre were obtained by micrometry of the cine image. Comparisons of values obtained after periods of light adaptation with the preceeding and subsequent periods of darkness show no significant changes in vessel calibre (at P greater than 0.95 level, confidence limits +/- 17% of the mean) while three of 14 comparisons show significant but inconsistent changes in linear flow velocity (at P greater than 0.95 level, confidence limits +/- 22% of the mean). A significant decrease (41%) in b-wave amplitude was seen in six of seven experiments after dark adaptation subsequent to exposure to light for a total of 60 min.