Real-time measurement of human optic nerve head and choroid circulation, using the laser speckle phenomenon

A modification of a previously described instrument that used the laser speckle phenomenon for noncontact two-dimensional analysis of the fundus tissue circulation was devised so that tissue circulation in the optic nerve head (ONH) or choroid of the human eye could be measured on a real-time basis. The fundus was illuminated by a diode laser spot and the image speckle was recognized by an area sensor. A quantitative index of blood velocity, normalized blur (NB), was calculated by a logistic board every 0.125 seconds for 7 seconds. Using this modified device, the average NB of the measurement field in the temporal ONH, free of visible surface vessels (NBONH), and that in the posterior choroid (NBch) of normal human eyes were measured. The coefficients of reproducibility of 1-minute interval measurements were 11.7% for the NBONH) and 8.7% for the NBch (each, an average of 5 pulses), and those of 24-hour interval measurements were 13.0% (NBONH) and 9.7% (NBch). The pulsatile component average of NBONH was 38.4% of mean NBONH; of NBch, 26.6% of the mean NBch.