VARIABILITY IN MEASUREMENT OF CENTRAL RETINAL ARTERY VELOCITY USING COLOR DOPPLER IMAGING

The purpose of our study was to test the reproducibility of the centra l retinal artery velocity measurements as made by color Doppler imagin g and pulsed Doppler spectral tracings and to define the optimal locat ion for placement of the sample volume. We used the Siemens Quantum (Q 2000) with a 7.5 MHz linear array transducer to identify the central retinal artery and record its velocity. Eleven eyes from 11 normal sub jects were evaluated for the peak systolic central retinal artery velo city in two positions, the first posteriorly in the optic nerve at an average of 3.56 mm from the surface of the optic disc and the second a t an average of 1.76 mm from the surface of the optic disc. We then us ed a color-flow threshold to identify and record the point of maximal velocity. The range of systolic velocities in the 11 eyes was from 5.8 5 to 22.51 cm/sec. The peak systolic velocity posteriorly in the optic nerve averaged 8.16 cm/sec, whereas near the surface of the optic dis c the velocity averaged 13.89 cm/sec (70.2% higher). Using the color f low threshold method, the maximal velocity was located at an average o f 1.98 mm from the surface of the optic disc. Our data show that large differences exist in measured central retinal artery velocity that de pend on the location of the measurement, and that color-flow threshold ing is valuable in locating the optimal location for pulsed Doppler sp ectral recording.