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Human basic tear fluid osmolality
Author(s) -
White Katherine M.,
Benjamin William J.,
Hill Richard M.
Publication year - 1993
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.1993.tb04631.x
Subject(s) - osmole , osmometer , tonicity , mathematics , chemistry , ophthalmology , zoology , medicine , chromatography , biology , biochemistry
. Osmolalities of 100 human inferior tear prism fluid samples collected from two subjects and 100 standard solution samples (290 mOsm/Kg) were determined from their melting‐point temperatures with the Clifton Nanoliter Osmometer. Accuracy and reliability comparisons were made for endpoints obtained using a single‐sample simultaneous‐recalibration (SS/SR) strategy, vs a lowest‐of‐six periodic‐recalibration (LS/PR) strategy. Tear fluid osmolality values based on the LS/PR strategy were significantly lower (hypotonic) than for the SS/SR strategy (overall mean = 302.4 and 307.8 mOsm/Kg, respectively; p <0.0012). The mean difference (5.4 mOsm/Kg) resulted from the combined effects of machine drift and reduced reliability of endpoint determination for tear fluid in comparison to that of a homogenous standard solution. LS/PR osmolality was linearly correlated to SS/SR osmolality with a slope of 0.433 and the two endpoint strategies resulted in equivalent values at 298.4 mOsm/Kg. Eighty‐four percent (84%) of individual osmolality readings were greater than 298.4 mOsm/Kg, and an ‘averaging‐type’ effect caused LS/PR osmolalities to be increasingly less than SS/SR values above this value. These outcomes from two subjects were approximated by a parallel statistical model. We suggest that physiological representation of basic human tear fluid is more accurate using the single‐sample simultaneous‐recalibration strategy. Basic human tear prism fluid is more hypertonic and has a greater within‐subject range in normal (nondry eye) humans than previously realized.