title: Measurement of basal tear turnover using a standardized protocol. European concerted action on ocular fluorometry.
abstract: BACKGROUND
  The aim of this study was to compare basal tear turnover values of healthy volunteers in different countries.
  
  
  METHODS
  Healthy volunteers aged between 20 and 70 years were selected in three European cities. Basal tear turnover values were calculated according to a standardized protocol from the decay of the fluorescein concentration in tears after instillation of 1-microliters drop of fluorescein in the conjunctival sac. Fluorescein concentration was measured with identical commercial fluorophotometers. A mono-exponential decay of fluorescein was assumed to represent basal tear flow.
  
  
  RESULTS
  The mean tear turnover values were 13.1%/min +/- 4.6 SD (n = 4), 16.0%/min +/- 5.2 SD (n = 24) and 17.5%/min +/- 3.4 SD (n = 20) in Clermont-Ferrand (France), Leiden (The Netherlands) and Madrid (Spain), respectively. The differences between the values were not significant (Mann-Whitney test P > 0.09).
  
  
  CONCLUSIONS
  The tear turnover in the different cities was similar. The methods used were simple and the software easy to use.
authors.affiliation: Department of Ophthalmology, University Hospital, Leiden, The Netherlands.
authors.forename: J A
authors.initials: JA
authors.lastname: van Best
authors.forename: J M
authors.initials: JM
authors.lastname: Benitez del Castillo
authors.forename: L M
authors.initials: LM
authors.lastname: Coulangeon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D005060:Europe; D005123:Eye / Q000378:metabolism*; D005260:Female; D019793:Fluorescein; D005452:Fluoresceins / Q000032:analysis; D015590:Fluorophotometry / Q000379:methods*; D005902:Glaucoma, Open-Angle / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D013666:Tears / Q000378:metabolism*
chemical_list: D005452:Fluoresceins; D019793:Fluorescein