title: Evaluation of a new tear osmometer for repeatability and accuracy, using 0.5-microL (500-Nanoliter) samples.
abstract: OBJECTIVE
  To evaluate the repeatability and accuracy of a new tear osmometer that measures the osmolality of 0.5-microL (500-nanoliter) samples.
  
  
  METHODS
  Four standardized solutions were tested with 0.5-microL (500-nanoliter) samples for repeatability of measurements and comparability to standardized technique. Two known standard salt solutions (290 mOsm/kg H2O, 304 mOsm/kg H2O), a normal artificial tear matrix sample (306 mOsm/kg H2O), and an abnormal artificial tear matrix sample (336 mOsm/kg H2O) were repeatedly tested (n = 20 each) for osmolality with use of the Advanced Instruments Model 3100 Tear Osmometer (0.5-microL [500-nanoliter] sample size) and the FDA-approved Advanced Instruments Model 3D2 Clinical Osmometer (250-microL sample size).
  
  
  RESULTS
  Four standard solutions were used, with osmolality values of 290, 304, 306, and 336 mOsm/kg H2O. The respective precision data, including the mean and standard deviation, were: 291.8 +/- 4.4, 305.6 +/- 2.4, 305.1 +/- 2.3, and 336.4 +/- 2.2 mOsm/kg H2O. The percent recoveries for the 290 mOsm/kg H2O standard solution, the 304 mOsm/kg H2O reference solution, the normal value-assigned 306 mOsm/kg H2O sample, and the abnormal value-assigned 336 mOsm/kg H2O sample were 100.3, 100.2, 99.8, and 100.3 mOsm/kg H2O, respectively.
  
  
  CONCLUSIONS
  The repeatability data are in accordance with data obtained on clinical osmometers with use of larger sample sizes. All 4 samples tested on the tear osmometer have osmolality values that correlate well to the clinical instrument method. The tear osmometer is a suitable instrument for testing the osmolality of microliter-sized samples, such as tears, and therefore may be useful in diagnosing, monitoring, and classifying tear abnormalities such as the severity of dry eye disease.
authors.affiliation: Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Elvin H
authors.initials: EH
authors.lastname: Yildiz
authors.forename: Vincent C
authors.initials: VC
authors.lastname: Fan
authors.forename: Hina
authors.initials: H
authors.lastname: Banday
authors.forename: Lakshmi V
authors.initials: LV
authors.lastname: Ramanathan
authors.forename: Ratna K
authors.initials: RK
authors.lastname: Bitra
authors.forename: Eileen
authors.initials: E
authors.lastname: Garry
authors.forename: Penny A
authors.initials: PA
authors.lastname: Asbell
mesh_terms: D019411:Clinical Laboratory Techniques / Q000295:instrumentation* / Q000592:standards; D006801:Humans; D009883:Ophthalmic Solutions / Q000737:chemistry; D009994:Osmolar Concentration; D015203:Reproducibility of Results; D018401:Sample Size; D013666:Tears / Q000737:chemistry*; D014985:Xerophthalmia / Q000175:diagnosis
chemical_list: D009883:Ophthalmic Solutions