CHOROIDAL BLOOD-FLOW MEASUREMENT IN THE MONKEY BY CLEARANCE OF INDOCYANINE GREEN DYE

We measured choroidal blood flow in the rhesus monkey by determining the rate of clearance of indocyanine green dye from the choroidal circulation. Measurements were made by rapidly (0·2 sec) injecting indocyanine green dye (5 mg/ml), in 0·1 ml increments, into the common carotid artery and photoelectrically monitoring its concentration in a vortex vein. Light with peak transmittance 797 nm (half bandwidth 15 nm) was transmitted to the vein using a specially constructed fiber optic bundle. Transmitted light was collected with a second fiber optic bundle and conducted to a photodetector-amplifier circuit. The output of this circuit was a voltage linearly proportional to the amount of transmitted light and hence the venous concentration of indocyanine green dye. This was recorded on both a polygraph and an FM analog tape recorder. The clearance curves were analyzed to give the blood flow rate, which was based on the rate of washout of the dye. Within the normal range of perfusion pressures (90-110 mmHg), curves were all monoexponential which allowed us to analyze them with a first order model of the choroidal circulation. At normal perfusion pressure the choroidal blood flow rate was 17±6 ml/min/ml of choriocapillaris (mean±s.d.). With measured values of the choriocapillaris volume this indicates a blood flow rate of approximately 0·2 ml/min in the choroid. © 1979.