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Original article
Barriers to clinical uptake of tear osmolarity measurements
  1. Santosh Khanal,
  2. Thomas J Millar
  1. School of Natural Sciences, University of Western Sydney, Australia
  1. Correspondence to Thomas J Millar, School of Natural Sciences, University of Western Sydney, Locked Bag 1797, Penrith NSW, Australia 2751; t.millar{at}


Aim The aim of the study was to examine the possibilities of measuring tear osmolarity in a general clinical setting, and to identify the barriers preventing the uptake of new methodologies for its measurement.

Methods Five non-contact-lens wearers were recruited to evaluate the diagnostic capability of the TearLab. Three osmolarity measurements were taken at 1 min intervals in the morning at 09:00, midday between 12:00 and 13:00 and afternoon at 16:00 for two consecutive days. Forty more osmolarity measurements were carried out at different times on one subject with low and one subject with high tear osmolarity over 4 months. The osmolarity of a standard solution, 290 mOsm/l, was measured 19 times alternatively with the TearLab by two examiners.

Results Consecutive tear osmolarity readings in an individual varied up to 35 mOsm/l, but an average over three readings was found to be a reliable indicator of tear osmolarity at 95% confidence level. For population studies, a power analysis based on the variability of the data showed that three repeat measurements would be required to obtain reliable data for a study with <50 subjects, whereas one measurement would suffice for 490 or more subjects. There were no interobserver or interinstrumental differences, but readings obtained for the standard solution varied up to 89 mOsm/l.

Conclusion Three consecutive readings are required with the TearLab to obtain a reliable measure of tear osmolarity. The variation in recorded tear osmolarity makes it difficult to use the technique for the diagnosis of mild dry eye.

  • Tears

Statistics from


  • Part of the work was presented at the 6th International Meeting of Tear Film and Ocular Surface Society, September 2010.

  • Funding Australian Government linkage project scheme no LP0776482 and the University of Western Sydney Seed Grant.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the University of Western Sydney Australia.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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