title: Assessment of tear film osmolarity using the TearLab™osmometer in normal dogs and dogs with keratoconjunctivitis sicca.
abstract: OBJECTIVE
  To evaluate repeatability and reproducibility of tear osmolarity measured using the TearLab™osmometer in normal dogs and to assess its diagnostic potential in dogs with keratoconjunctivitis sicca (KCS).
  
  
  METHODS
  Beagle dogs; six normal and five with KCS.
  
  
  METHODS
  Tear osmolarity and Schirmer tear test-1 (STT-1) values were obtained at various times. Normal dogs were assessed for diurnal variation and repeatability and reproducibility of measurements. Dogs with KCS were evaluated before and after 5 months' topical twice-daily therapy with 2% cyclosporine.
  
  
  RESULTS
  Mean ± SD tear osmolarity (mOsm/L) was significantly higher in normal dogs (337.4 ± 16.2) than in dogs with KCS before therapy (306.2 ± 18.0; P < 0.0001), but not following therapy with 2% cyclosporine (330.5 ± 13.7; P = 1.00). Osmolarity readings lower than 325.5 mOsm/L were suggestive of KCS (84.8% sensitivity and 87.1% specificity). In normal dogs, tear osmolarity readings were stable during the daytime (P = 0.99). Repeated measurements revealed high variability and typically poor-to-moderate repeatability and reproducibility, although this was improved by taking three successive measurements at each session. Considering combined data from all dogs, a positive correlation existed between STT-1 and tear osmolarity measurements (Pearson's correlation test, P = 0.04, r = 0.62).
  
  
  CONCLUSIONS
  Canine tear osmolarity as determined by TearLab™osmometer was variable, required multiple readings to be informative, and differed from values reported for humans. Dogs with KCS had a lower tear osmolarity than did normal dogs, and this increased following cyclosporine therapy.
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, CA, USA.
authors.forename: Lionel
authors.initials: L
authors.lastname: Sebbag
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Shin Ae
authors.initials: SA
authors.lastname: Park
authors.affiliation: Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Philip H
authors.initials: PH
authors.lastname: Kass
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Maggs
authors.affiliation: Department of Research and Development, Allergan plc, Irvine, CA, USA.
authors.forename: Mayssa
authors.initials: M
authors.lastname: Attar
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA, USA.|Department of Ophthalmology & Vision Science, School of Medicine, University of California, Davis, CA, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Murphy
mesh_terms: D000818:Animals; D016572:Cyclosporine / Q000627:therapeutic use; D004283:Dog Diseases / Q000175:diagnosis* / Q000188:drug therapy; D004285:Dogs; D005260:Female; D006801:Humans; D007638:Keratoconjunctivitis Sicca / Q000175:diagnosis / Q000188:drug therapy / Q000662:veterinary*; D009994:Osmolar Concentration; D015203:Reproducibility of Results; D013666:Tears / Q000737:chemistry*
chemical_list: D016572:Cyclosporine
keywords: TearLab™; diagnostic tool; dog; keratoconjunctivitis sicca; osmolarity; tear film