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Related Experiment Videos

Human basic tear fluid osmolality. I. Importance of sample collection strategy

K M White1, W J Benjamin, R M Hill

  • 1School of Optometry, University of Alabama at Birmingham.

Acta Ophthalmologica
|August 1, 1993
PubMed
Summary

Human tear fluid osmolality is higher than previously thought. Using a non-invasive method to collect tear prism fluid samples provides more accurate osmolality measurements, avoiding reflex stimulation from biomicroscopy.

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Area of Science:

  • Ophthalmology
  • Physiology
  • Biophysics

Background:

  • Tear fluid osmolality is a critical physiological parameter.
  • Previous collection methods may have influenced osmolality readings.
  • Accurate tear osmolality is vital for understanding ocular surface health.

Purpose of the Study:

  • To accurately determine the osmolality of human tear prism fluid.
  • To compare osmolality measurements obtained with and without biomicroscopy.
  • To assess the impact of collection methods on tear fluid osmolality.

Main Methods:

  • Collected 200 human tear prism fluid samples from two subjects.
  • Measured osmolality using melting-point temperatures with a Clifton Nanoliter Osmometer.
  • Compared samples collected with and without biomicroscopy, and before/after a 10-min interval.

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Main Results:

  • Tear fluid collected with biomicroscopy had significantly lower osmolality (mean 299.5 mOsm/kg) than without (mean 306.6 mOsm/kg).
  • The 10-minute interval did not affect osmolality in samples collected without biomicroscopy.
  • Biomicroscopy likely induced reflex stimulation, lowering measured osmolality.

Conclusions:

  • Basic human tear prism fluid is at least 7 mOsm/kg more hypertonic than generally realized.
  • Avoiding reflex-inducing collection methods like biomicroscopy yields more physiologically accurate tear osmolality.
  • Repetitive tear fluid collections can be made without significantly altering osmotic outcomes if non-invasive methods are used.