Eye-tracking laser Doppler velocimeter stabilized in two dimensions: principle, design, and construction

We developed an eye-tracking laser Doppler velocimeter to minimize eye-movement artifacts in the study of ocular hemodynamics in humans. The instrument compensates for both horizontal and vertical eye motions by using galvanometer mirrors controlled by a dual-Purkinje eye tracker. The performance of the instrument is demonstrated in a preliminary study of retinal arterial blood velocity in a normal subject. The subject's fixation point was adjusted manually to oscillate through a 2.3-deg span at 0.3 Hz. In spite of this motion the pulsatile velocity waveform of the heart cycle could be continuously recorded. Without eye tracking the velocity waveform was lost after the initiation of movement.