Dry Eye Information

How Tear Film Instability Occurs

Tear Film Instability

tear film instability

damaged corneal cells

A common cause of tear film instability is corneal surface desiccation. Damage to corneal epithelial cells means loss of the delicate structures that anchor mucins to the eye's surface, which in turn leads to tear film instability.

When mucins cannot attach, the exposed hydrophobic corneal surface repels aqueous components of the tear film causing additional damage. As this progresses, the tear film further destabilizes, increasing tear evaporation and osmolarity.

When destabilization ("break-up") happens before
a blink can occur, the exposed cornea is subject to further damage.

See How Tear Film Instability Can Occur

Some patients present with extensive punctate epitheliopathy but minor complaints, while others manifest minimal staining but are extremely uncomfortable. A Schirmer's test in this latter group may show normal wetting and further confound the diagnosis. However, these patients may have dry eye disease as a result of tear film instability secondary to tear component abnormality or imbalance. This underscores the importance of measuring TFBUT in the evaluation of suspected dry eye disease. An artificial tear can have therapeutic value by improving tear film stability to extend TFBUT. 1


  1. Ousler GW, Emory TB, Welch D, Abelson MB. Factors that influence the inter-blink interval (IBI) as measured by the ocular protection index (OPI). Presented at: The Association of Research in Vision and Ophthalmology (ARVO); 2002.

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SYSTANE® Lubricant Eye Drops helps protect eyes from dry eye and keeps them lubricated throughout the day.

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