Purpose: To obtain better insight into the process of dye extravasation in the human choroid during sodium fluorescein angiography of the ocular fundus.
Methods: Sodium fluorescein angiography using a scanning laser ophthalmoscope was performed on the right eye of five healthy volunteers. The dose of sodium fluorescein was chosen to avoid quenching in the ocular vessels. The time-intensity curve of background fluorescence was measured and its shape compared with that of the time-intensity curve of a retinal artery, representing an intravascular compartment. Significant dye extravasation is expected to cause a marked change in shape of the time-intensity curve of background fluorescence as compared with the intravascular time-intensity curve due to long washout of dye from the interstitial space of the choroid.
Results: In all five subjects, the time-intensity curve of background fluorescence and the retinal artery proved to be quite similar in shape until several seconds after peak intensity of the first bolus passage.
Conclusion: Background fluorescence originates mainly from intravascular compartments during the early phase of the sodium fluorescein angiogram.