By using more than one wavelength for excitation, and often two separate detectors, we have developed Fluorotrons for measuring more than one fluorophore in a single scan. One application for this is to measure fluorescein and its metabolite, fluorescein glucuronide. Another is to tag one compound with fluorescein, and another with rhodamine, so their pharmacokinetics may be tracked separately.
Selected Reference:
Sander B, Larsen M, Moldow B, Lund-Andersen H. Diabetic macular edema: passive and active transport of fluorescein through the blood-retina barrier. Invest Ophthalmol Vis Sci 42(2):433-8 (2001). PubMed
Takahashi J, Mori F, Hikichi T, Yoshida A. Effect of acetazolamide on outward permeability of blood-retina barrier using differential vitreous fluorophotometry. Curr Eye Res 23(3):166-70 (2001). PubMed
McLaren JW, Brubaker RF. Measurement of fluorescein and fluorescein monoglucuronide in the living human eye. Invest Ophthalmol Vis Sci 27(6):966-74 (1986). PubMed