Estimating basal tear osmolarity in normal and dry eye subjects

Willshire, Catherine and Buckley, Roger J. and Bron, Anthony J. (2018) Estimating basal tear osmolarity in normal and dry eye subjects. Contact Lens and Anterior Eye, 41 (1). pp. 34-46. ISSN 1476-5411

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Purpose: Tear osmolarity (tOsm) is used as a measure of severity in dry eye disease (DED) and has been proposed as an index of body hydration. In DED the level of tear hyperosmolarity is compared with that of a control population. It is proposed here that a better index of body hydration and a more valid reference point in DED can be acquired by measuring the tOsm after a period of evaporative suppression. Method: 8 normal and DED subjects were recruited, their tOsm measured in uncontrolled environmental 'clinic conditions'. Then in experiment 1 they entered a controlled environment chamber and had tOsm measured after 45 minutes of eye closure and then, with the eyes open, at 15 minute intervals for a further 45 minutes, at a relative humidity (RH) of 45%. Alternatively, in experiment 2, they had tOsm measured every 15 minutes for 45 minutes during exposure to 70% RH, as a separate measure to suppress evaporation. Results: A significant decrease in tOsm occurred in both normal and DED subjects after lid closure in experiment 1 (normal RE p = 0.015; normal LE p = 0.006; DED RE p = 0.0002; DED LE p = 0.01). The tOsm also fell slightly after exposure to 70% RH in experiment 2 significant in the LE of normal group only (normal LE p = 0.045). Conclusions: Suppression of tear evaporation resulted in a fall in tOsm, close to that of plasma osmolarity (285–295 mOsm/L). It is proposed that this new measure, termed Basal Tear Osmolarity (BTO), could provide a valuable index of plasma osmolarity and hence of body hydration and in DED, a personal baseline against which to gauge the severity of tear hyperosmolarity.

Item Type: Journal Article
Keywords: Basal Tear Osmolarity, Controlled Environment Chamber, Dry Eye Diseas, Plasma osmolality, Systemic dehydration, Tear osmolarity
Faculty: ARCHIVED Faculty of Medical Science (until September 2018)
Depositing User: Ian Walker
Date Deposited: 22 Dec 2017 09:56
Last Modified: 09 Sep 2021 18:57

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