[Noninvasive two-dimensional analysis of iridial circulation using the laser speckle phenomenon]

We have developed an apparatus using the laser speckle phenomenon for noninvasive two-dimensional measurement of the peripheral circulation of the iris. The normalized blur of the speckle pattern (NB-value) was adopted as an index of the blood velocity in the tissue. It was found that the average NB-value of the pigmented rabbit iris was gradually increasing from pupil margin to periphery. The coefficient of variation of the NB-value in the middle area of the iridial width was the smallest. The coefficient of reproducibility of the NB-value measured in the same area twice at 5-minute intervals was 8.8%, and that at 24-hour intervals was 14.1%. The NB-value of the iris showed a good correlation (r = 0.57, p < 0.0072 n = 20) with the iridial blood flow rate measured at the same time by the microsphere technique when intraocular pressure was adjusted to 20 mmHg or 40 mmHg. This result suggests that the NB-value can be useful for quantitative assessment not only of the blood velocity but also of the blood flow rate in the iridial tissues.