A fluorescent vesicle system for the measurement of blood velocity in the choroidal vessels.

BACKGROUND AND OBJECTIVE Evaluation of the pathophysiologic mechanisms involved in the choroidal circulation is difficult because of the presence of the retinal pigment epithelium. The authors have developed a technique for measuring blood velocity in individual choroidal vessels using the scanning laser ophthalmoscope and intravenously injected indocyanine green encapsulated in multilamellar vesicles. In this report, the authors describe their attempts to measure choroidal blood velocity in three different regions of the choroid of the primate eye. MATERIALS AND METHODS A video-to-digital processor was used to digitize the video images of the choroid of a monkey at a sample rate of 1/30 of a second. The blood velocity in the selected choroidal vessel segments was calculated by measuring the distance the liposome traveled in a given time. RESULTS The average blood velocities were 5.16 mm/s under the macula, 4.04 mm/s in the vortex vein system, and 2.03 mm/s in the choroidal circulation nasal to the optic nerve. CONCLUSION This technique is an effective method of measuring blood velocity in a primate model and has several important advantages compared with the dye dilution technique.