Tear turnover can be measured using the Fluorotron by instilling a drop of fluorescein in the tear film and measuring its dilution over time. The Fluorotron’s computer program can use the fluorescence scans to automatically compute tear turnover.
This type of measurement has also been used by some of our investigators to measure the tear turnover under different contact lens designs.
Selected References:
van Best JA, Benitez del Castillo JM, Coulangeon LM. Measurement of basal tear turnover using a standardized protocol. European concerted action on ocular fluorometry. Graefes Arch Clin Exp Ophthalmol 233(1):1-7 (1995). PubMed
McNamara NA, Polse KA, Brand RJ, Graham AD, Chan JS, McKenney CD. Tear mixing under a soft contact lens: effects of lens diameter. Am J Ophthalmol 127(6):659-65 (1999). PubMed
Meadows DL, Paugh JR, Joshi A, Mordaunt J. A novel method to evaluate residence time in humans using a nonpenetrating fluorescent tracer. Invest Ophthalmol Vis 43(4):1032-9 (2002). PubMed
A more complete bibliography can be found here.