Bio-speckle flowmetry for retinal blood flow diagnostics

Bio-speckle flowmetry for measuring the retinal blood flow velocity is described. The measuring principle is briefly discussed in comparison with the laser Doppler method. The basic properties of the photon correlation measurements including reproducibility were experimentally investigated with a rotating ground glass disk and for the normal human retina. The error was estimated to be less than 20% for in vivo measurements. By using a glass capillary model, the reciprocal of correlation time was calibrated to the mean flow velocity with a consideration of the effects of the vessel diameter and the background reflectance. The blood flow volume rate in the human retina was estimated by using the calibrated velocity and the vessel diameter. The results compared well with those reported in the literature, and show the usefulness of this flowmetry for clinical diagnostic purposes.