I thank Flower for his comments. I am sorry that he failed to confirm my results of ICG angiography. The most important part of my letter was that ICG dye binds with serum protein with extraordinarily slow speed compared with other organic dyes, such as fluorescein sodium. Furthermore, I tried to measure the accurate binding time of ICG and serum protein using a stopped-flow meter (Union Technology Co, Tokyo, Japan). It took more than 10 seconds, which exceeded the limitation of the capability of the measurement system before reaching the maximum binding, whereas it took 10 milliseconds for the fluorescein sodium and serum protein to bind. This confirmed our previous data indicating that the peak absorption shifts from 780 nm to 805 nm very slowly along the time course after the dye injection. The absorption kinetics should be considered for the filter setting to detect the fluorescence efficiently.
Yoneya S. Does Preinjection Binding of Indocyanine Green to Serum Actually Improve Angiograms?-Reply. Arch Ophthalmol. 1994;112(9):1138-1139. doi:10.1001/archopht.1994.01090210021004