Dry Eye Information

Tear Film Break-Up Time

Tear Film Break Up Time

The time required for the ocular surface to lose cohesive surface wetting after each blink is referred to as the tear film break-up time (TFBUT).

Dry areas will appear as part of normal evaporation and diffusion of tears. In a normal healthy eye, dry areas start occuring between blinks at about 10-12 seconds, and an urge to blink is triggered.

When TFBUT is less than the blink rate, the ocular surface is left unprotected, and the signs and symptoms of dry eye are exacerbated.

See Tear Film Break-Up Time

Ocular Protection Index

The Ocular Protection Index (OPI) demonstrates how the TFBUT and inter-blink interval (IBI) interact to protect the corneal surface.1 If the amount of time between blinks is longer than TFBUT, an insufficient tear film leaves the corneal epithelial cells unprotected, exacerbating the signs and symptoms of dry eye.

Ocular Protection Index

See the Ocular Protection Index

When the TFBUT exceeds the inter-blink interval the signs and symptoms of dry eye may be minimized.

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Symptomatic Break-up (SBUT) Time Test 1

There is no single test to diagnose dry eye. However, a simple indicator is the Symptomatic Tear Break-up Time test. Symptomatic Tear Break-up Time is determined with the following steps:

  1. Obtain a stop watch or clock;
  2. Have the patient blink two times then stare straight ahead;
  3. Ask the patient to avoid blinking as long as possible AND to indicate when ocular discomfort begins (itchiness, foreign body sensation, etc.);
  4. Record the amount of time (in seconds) that transpires between the last complete blink and the moment they experience ocular discomfort.

The recorded time represents a subjective response to loss of ocular protection.

This is considered a valid measurement of tear break-up, as research has shown nearly 4 out of 5 patients experience ocular awareness followed by discomfort within 1 second of TFBUT.2

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  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). (Poster presentation) The Association of Research in Vision and Ophthalmology (ARVO), 2002.
  2. Nally L, Ousler GW, Abelson MB. Ocular discomfort and tear film break-up time in dry eye patients: a correlation. IOVS 2000 41;4(ARVO Abstract):1436.

SYSTANE®

SYSTANE®

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

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SYSTANE®

SYSTANE®

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

Learn More