Compensation of eye movements in retinal speckle flowmetry using flexible correlation analysis based on the specific variance
Bio-speckle flowmetry using the photon correlation technique is useful for measuring the retinal blood flow velocity. In practical situations, however, it often suffers from eye- movement artifacts and other external moving factors. To solve this problem, we studied in this paper a flexible correlation analysis, by which the blood flow information can be effectively extracted from erroneous data influenced by displacement of the measuring point. The signal-analyzing system including the photon correlator directly stores the sequential counts of photoelectron pulses into a memory. After measurements, the stored data are read out and used to calculate the first-order statistics of time-integrated bio- speckles and the autocorrelation function with an arbitrary delay-time unit for an arbitrary period. These results are used to specify and to eliminate the erroneous parts of data due to the displacement of the measuring point. The usefulness of this technique was verified for a glass capillary model and human retinal vessels.