Fluorescein is used to strain the cornea. After the excess fluorescein is rinsed from the tear film, enough time it allowed for the fluorescein to come into a steady state condition between the cornea and the anterior chamber. Fluorotron scans are then performed to determine the cornea (A) and anterior chamber (B) concentrations over time. The Fluorotron’s computer software can then use these concentration values to calculate aqueous turnover.
Selected Reference:
van Best JA, Diestelhorst M, Leite E, Fantaguzzi S, Schalnus R. Corneal endothelial permeability and aqueous humor flow using a standard protocol. Graefes Arch Clin Exp Ophthalmol 233:582-91 (1995). PubMed
Toris CB, Fan S, Johnson TV, Camras LJ, Hays CL, Liu H, Ishimoto BM. Aqueous Flow Measured by Fluorophotometry in the Mouse. Invest Ophthalmol Vis Sci. 57(8):3844-52 2016. PubMed Full Article
A more complete bibliography can be found here.