Evaluation of the dynamics of choroidal circulation in experimental acute hypertension using indocyanine green-stained leukocytes

Purpose: To evaluate the dynamics of choroidal circulation in experimental acute hypertension, using the indocyanine green leukocyte angiography (ILA) method, which the authors have developed for the evaluation of leukocyte dynamics in choroidal circulation. Methods: Japan White rabbits were used in the present study. Leukocytes were collected by centrifugal separation of the autologous blood, and were stained with indocyanine green (ICG) dye. The ICG-stained leukocyte fluid was injected into an ear vein, and fundus images were obtained by infrared laser and a scanning laser ophthalmoscope. Experimental acute hypertension was induced by the intravenous drip injection of angiotensin II (AII). Results: The fluorescent dots rapidly moved in choroidal arteries at a decreasing velocity, passed very slowly through choroidal capillaries and drained into choroidal veins. Under normal blood pressure, the mean leukocyte velocities in arteries, capillaries and veins were 8.63±1.68, 0.52±0.07, and 6.96±2.20 mm/s, respectively. On the other hand, the respective mean velocities in acute hypertension induced by AII were 13.50±1.82, 0.81±0.09, and 10.54±3.91 mm/s. Besides flow velocity, no change in leukocyte dynamics was observed. Conclusions: Under the condition of acute hypertension induced by AII, leukocytes moved faster in the total choroidal circulation (from arteries to veins) compared to their velocity under the condition of normal blood pressure. Blood velocities might increase in the total choroidal circulation at an early stage in acute hypertension induced by AII, resulting in increased choroidal blood flow. ILA makes it possible to evaluate the changes in choroidal circulation under various pathologic conditions.