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

Abstract

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.