[Noninvasive two-dimensional analysis of retinal microcirculation using the laser speckle phenomenon--II. Comparison...

We have recently developed an apparatus for noninvasive two-dimensional analysis of the retinal microcirculation using the laser speckle phenomenon. The fundus is illuminated by an argon laser spot and its image speckle is detected by an area sensor. The difference between the average of output data and the output data for successive scannings of the image speckles at the sensor plane is calculated to give the value of normalized blur (NB), which is a quantitative index of tissue blood flow velocity. In pigmented rabbit eyes, the coefficient of reproducibility was 8% when the same area of retina was measured twice at 5-minute intervals and 13% at 24-hour intervals. The NB values in the retina free of visible vessels were recorded under various levels of intraocular pressure ranging from 10 to 80 mmHg and the results were compared with the blood flow rate determined with the colored microsphere technique. A linear correlation was found between the former and the latter, which suggested that the NB value also parallels the tissue blood flow rate.