Fig. 2.

Dependence of the retinal arterial waveform profile upon the Doppler frequency range. All curves are obtained from the same LDH measurements, only with different processing. (a) and (b): dynamic raw power Doppler and power Doppler corrected from the spatial average for three frequency ranges: 6–10 kHz in the pink solid line, 10–20 kHz in the red dashed line, and 20–37 kHz in the deep red dotted line. (c) and (d): waveform profile averaged over three cardiac cycle with variations normalized between 0 and 1. The waveform profile calculated with the frequency band 6–10 kHz shows a pulsatile signal tainted by bulk motion (attributed by unexpected oscillations); the normalized arterial waveform calculated with the very high frequency range appears steeper due to the velocity thresholding effect.