[Effect of mannitol on human retinal blood flow].

The effect of hyperosmotic agents (20% mannitol) on the retinal circulation was evaluated in 14 eyes of 7 normal subjects. Laser speckle retinal blood flow velocimetry with simultaneous real-time measurement of retinal vessel diameter was used. Experiments were performed in a double-masked crossover design and each subject was given either 20% mannitol or physiological saline solution by intravenous drip. The retinal blood flow rate was measured just before the administration of the agents and after the intravenous drips. After the 20% mannitol administration, intraocular pressure was reduced and ocular perfusion pressure, retinal blood flow velocity, and retinal blood flow rate increased significantly (paired t-test, p < 0.01). There was not statistically significant difference between the retinal blood flow rate before and after the administration of physiological saline solution (p > 0.05), but the retinal blood flow velocity increased significantly (p < 0.05). The ratio between the retinal blood flow rate before and after the administration of 20% mannitol was statistically larger than that of physiological saline solution (p < 0.05).