Vasoconstrictive effects of sodium fluorescein on retinal vessels is increased by light exposure.
OBJECTIVE
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 approximately 85% of the initial vessel diameter in retinal arterioles and veins. Under dimly lit conditions, the vasoconstrictive effect of sodium fluorescein was still evident but the constriction was significantly smaller (p < 0.05) in both arteries and veins, reaching approximately 91% and 93%, respectively.


CONCLUSIONS
Sodium fluorescein induced light-dependent vasoconstrictive effects on the retinal vasculature of the pig. Should a similar effect be present in human retinal vessels, then reduced illumination level may limit the vasoconstrictive effects of sodium fluorescein when used in routine ophthalmic examinations.
Su
Er-Ning
EN
Centre for Ophthalmology and Visual Science, The University of Western Australia, Perth, Australia.
Cringle
Stephen J
SJ
Yu
Dao-Yi
DY
D000818:Animals; D001160:Arterioles / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000502:physiology; D019793:Fluorescein / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000494:pharmacology*; D008027:Light; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D012039:Regional Blood Flow; D012161:Retinal Artery / Q000502:physiology*; D012169:Retinal Vein / Q000502:physiology*; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects* / Q000528:radiation effects*; D014699:Venules / Q000502:physiology
D005456:Fluorescent Dyes; D019793:Fluorescein