Laser Doppler velocimetry stabilized in one dimension

Routine use of LDV for measurement of retinal hemodynamics has proven difficult. One reason is the susceptibility of the measurement to eye movement. Valid data are often distributed among data obtained while the beam is decentered or completely off the vessel. One remedy is to develop complex rejection criteria in an effort to circumvent the problem. The authors discuss a more direct solution, the stabilization of the incident laser beam on the target retinal vessel. A valid measurement of V _max corresponds to measuring the fastest component of flow; even slight decentering of the beam can bias the measurement of V _max to smaller values. Stabilization of the beam on the vessel center provides a more reliable measure of V _max.