[An apparatus using laser speckle phenomenon for noninvasive 2-dimensional analysis of choroidal microcirculation]

A new instrument using the laser speckle phenomenon for noninvasive 2-dimensional analysis of the choroidal microcirculation was developed. The fundus was illuminated with a diode laser spot and its image speckle was detected with an area sensor. The difference between the average of the output data (I-mean) and the output data from successive scannings of the image speckles at the sensor plane was calculated and integrated to give as D-mean, and I-mean/D-mean was defined as normalized blur (NB), which is a quantitative index of blood flow velocity. The results were displayed in color graphics showing the 2-dimensional variation of the NB level in the area of interest. The NB had good correlation with the speed measured on ground glass in the range between 2 and 130mm/sec. Using this instrument, the effect of intraocular pressure on the chroidal circulation of the rabbit was studied. The coefficient of reproducibility was 6.9% when measured in the same area twice at 5-minute intervals. A stepwise reduction in the ocular perfusion pressure was introduced by elevating the intraocular pressure manometrically. A linear correlation was found between the NB and the ocular perfusion pressure.