Vasoconstrictive Effects of Sodium Fluorescein on Retinal Vessels Is Increased by Light Exposure

Purpose: To determine whether clinically relevant doses of sodium fluorescein produce changes in vascular tone in retinal arterioles and veins and whether any such effects were light dependent. Methods: Segments of porcine retinal arterioles and veins were dissected, cannulated, and perfused and their outer diameter monitored during intraluminal application of increasing doses (10− 10 to 10− 3 g/ml) of sodium fluorescein under either brightly lit (350 lux) or dimly lit (4 lux) conditions. The significance of any induced change in vessel diameter was assessed in relation to the initial vessel diameter. Results: At the higher light level, sodium fluorescein produced a significant dose-dependent contraction in porcine retinal arterioles and veins with a threshold of 10− 5 g/ml and 10− 9 g/ml sodium fluorescein, respectively. At the maximal dose tested (10− 3 g/ml), vessel diameter was reduced to ∼ 85% of the initial vessel diameter in retinal arterioles and veins. Under dimly lit conditions, the vasoconstric...