Retinal circulation times in quantitative fluorescein angiography

Abstract

We tried to obtain an overview of the quantitative state of the retinal circulation. Optical density measurements by an image analyzer were performed on video fluorescein angiograms for the determination of dye-dilution curves. To ensure that curves with a sharp peak were obtained, 1 ml sodium fluorescein 10% was flushed with 20 ml physiological saline. From dilution curves of a retinal arteriole and the corresponding venule, various retinal circulation times, T (x) (x=1, 25, 50, 75, and 100) and Tm, were calculated. T(1) corresponds to the difference in the time of initial dye appearance; T(50), to the so-called half-maxim time difference; T(100), to the difference in the time to peak intensity; and Tm, to the mean circulation time. T(50) showed the best reproducibility when it was examined at 49 retinal regions of 10 healthy volunteers with a double video-fluorescein angiogram that was obtained within 1 min. Normal values (mean ± SD) at the temporal superior region of 37 healthy volunteers were as follows: T (1) = 0.87 ± 0.66 s, T(25)=1.52±0.48 s, T(50)=1.83±0.50 s, T(75)=2.12±0.56 s, T(t00) = 2.73±0.76 s, and Tm = 2.69±1.25 s. We believe that these values give a general overview of the quantitative state of normal retinal circulation.