Measurements of retinal blood flow using biospeckles: experiments with glass capillaries and in the normal human retina

Bio-speckles obtained from the human retina are used to measure the retinal blood-flow velocity on the basis of the photon correlation analysis. The reproducibility of measurements was experimentally investigated by using a stable rotating ground-glass disk and for the normal human retina, and the error was estimated to be less than 20%. Using a glass capillary model, the reciprocal of correlation time was calibrated to the mean flow velocity by considering the influences of the vessel diameter and the background reflectance. The blood- flow volume rate in the normal human retina was estimated by using the calibrated velocity and the vessel diameter. The results were well compared with the previous data, and show the usefulness of the method for clinical diagnostic purposes.