What is the role of tear breakup time (TBUT) testing in the workup of dry eye disease (keratoconjunctivitis sicca)?

Updated: Oct 09, 2017
  • Author: C Stephen Foster, MD, FACS, FACR, FAAO, FARVO; Chief Editor: Andrew A Dahl, MD, FACS  more...
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Answer

Tear breakup time (TBUT) is determined by measuring the interval between instillation of fluorescein and appearance of the first dry spots on the cornea. Measure it prior to instillation of any anesthetic eye drops. A fluorescein strip is moistened with saline and applied to the inferior cul-de-sac. After several blinks, the tear film is examined using a broad-beam of slit lamp with a blue filter for the appearance of the first dry spots on the cornea. Decreased TBUT of less than 10 seconds is considered abnormal, indicative of tear instability. Several devices can measure the TBUT objectively, including the Oculus Keratograph 5M.


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