Measurement of microcirculation in the optic nerve head by laser speckle flowgraphy and scanning laser Doppler flowmetry.

PURPOSE To evaluate and compare blood flow measurements by laser speckle flowgraphy and scanning laser Doppler flowmetry in the optic nerve head of normal volunteers. METHODS This prospective study included 60 eyes of 60 normal volunteers (50.0 years; range, 21 to 77 years). Measurements were taken at the temporal neuroretinal rim away from visible vessels. The square blur rate, a quantitative index of relative blood velocity, was measured by laser speckle flowgraphy. Using scanning laser Doppler flowmetry, volume, flow, and velocity were measured at the same neuroretinal rim locations. RESULTS The average square blur rate, volume, flow, and velocity were 7.11 +/- 1.65, 7.74 +/- 3.19, 151.85 +/- 70.63, and 0.53 +/- 0. 23 arbitrary units, respectively (n = 60). Square blur rate correlated significantly with flow and velocity (r =.361, P =.005; r =.359, P =.005, respectively). However, there was no significant correlation between square blur rate and volume (r =.101, P =.441). Although square blur rate decreased significantly with increasing age (r = -.375, P =.003), volume, flow, or velocity showed no significant correlation with age (r = -.249, P =.054; r = -.166, P =. 205; r = -.143, P =.275, respectively). Square blur rate also decreased significantly with mean blood pressure (r = -.315, P =. 014), but volume, flow, or velocity showed no significant correlation with mean blood pressure (r = -.159, P =.225; r = -.059, P =.654; r = -.043, P =.742, respectively). CONCLUSION We found only a weak correlation between the blood flow indexes, as measured by laser speckle flowgraphy and scanning laser Doppler flowmetry because of basic differences in the principles of measurement.