title: New method for viewing Krehbiel flow by polymethylmethacrylate particles suspended in fluorescein solution.
abstract: OBJECTIVE
  To investigate the changes in the tear flow velocities caused by ageing.
  
  
  METHODS
  Ninety-nine subjects (41 men, mean age 48.3 ± 20.7 years) were recruited from the Department of Ophthalmology of the Ehime University Hospital. None of the subjects had serious abnormalities of the external surface of the eye. The Krehbiel flow of tears was determined by 40-μm polymethylmethacrylate (PMMA) beads suspended in a fluorescein sodium solution (PPF). The movement of the beads was video recorded through a slit-lamp during normal blinking. The flow of the beads was determined with a Motion ANALYZER(®) software (KEYENCE Co., Osaka, Japan). The velocity of the beads in young age, 20-40 years, middle age, 41-60 years and old age, ≥61 years, groups was determined.
  
  
  RESULTS
  The equation describing the velocity (mm/second) of the PMMA particles as a function of age in the lower tear meniscus measured in the direction of the lacrimal punctum was Y = 2.49-0.04X, where Y = velocity and X = age (r(2) = 0.214; p < 0.0001). For the upper meniscus, the equation was Y = 4.83-0.05X (r(2) = 0.195, p < 0.0001). The average velocity was 0.70 ± 1.66 mm/second in the lower and 2.16 ± 1.93 mm/second in the upper tear meniscus (p < 0.0001). The particle velocity decreased significantly with increasing age, but no significant difference between the male and female groups except for the lower tear meniscus when all subjects were analysed.
  
  
  CONCLUSIONS
  The PPF technique is a simple method of examining Krehbiel flow of tears and may be used for evaluating functional nasolacrimal duct obstruction quantitatively.
authors.affiliation: Department of Ophthalmology, Ehime University School of Medicine, Ehime, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Ohta
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shiraishi
authors.forename: Yuri
authors.initials: Y
authors.lastname: Sakane
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zheng
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kamao
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Inoue
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ohashi
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001767:Blinking / Q000502:physiology; D005260:Female; D019793:Fluorescein / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism*; D015590:Fluorophotometry / Q000379:methods*; D006801:Humans; D007765:Lacrimal Apparatus / Q000502:physiology*; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D019904:Polymethyl Methacrylate / Q000378:metabolism*; D015203:Reproducibility of Results; D013535:Suspensions; D013666:Tears / Q000502:physiology*; D014741:Video Recording; D055815:Young Adult
chemical_list: D005456:Fluorescent Dyes; D013535:Suspensions; D019904:Polymethyl Methacrylate; D019793:Fluorescein
keywords: Krehbiel flow; fluorescein; lacrimal duct; polymethylmethacrylate; tear clearance; tear meniscus