Calculation of the diameter of the central retinal artery from noninvasive measurements in humans

PURPOSE: The aim of the present study was to calculate the diameter of the central retinal artery from results as obtained with non-invasive techniques in healthy young subjects. METHODS: Twenty-four healthy male subjects participated in this study. Total retinal blood flow was calculated from combined bi-directional laser Doppler velocimetry and measurement of retinal venous diameters using the Zeiss retinal vessel analyzer. Using these techniques red blood cell velocity and vessel diameters of all visible veins entering the optic nerve head were measured and total retinal blood flow was calculated. Blood flow velocity in the central retinal artery was measured with color Doppler imaging. Form these outcome parameters the diameter of the central retinal artery was calculated for each subject individually. RESULTS: In the present study cohort the mean retinal blood flow was 38.1 +/- 9.1 microl/min and the mean flow velocity in the central retinal artery was 6.3 +/- 1.2 cm/s. From these data we calculated a mean diameter of the central retinal artery of 163 +/- 17 microm. CONCLUSIONS: Our results are in good agreement with data obtained from in vitro studies. The data of the present study also indicate that one needs to be careful to interpret velocity data from the central retinal artery in terms of retinal blood flow.