The repeatability of the noninvasive blue field entoptic phenomenon method for measuring macular capillary blood flow

The speed of macular capillary blood flow can be estimated by using the blue field entoptic phenomenon. The technique uses a matching task in which the subject matches what is seen entoptically with a computer simulation of the phenomenon. In this study, we tested the repeatability of the leukocyte speed results obtained using this technique. Fourteen young subjects were tested on five different occasions. Group mean leukocyte speed did not vary significantly from one recording session to the next. However, readings for individuals varied substantially from one recording session to the next. This variability limits the usefulness of this technique for screening or monitoring macular blood flow in individuals.