Tear break-up time

Tear break-up time (TBUT) also known as tear film break-up time (TFBUT) is the time taken for the first dry spot to appear on the cornea after a complete blink. TFBUT measurement is an easy and fast method used to assess the stability of tear film. It is a standard diagnostic procedure in the dry eye clinics.[1] The volume of tear in the eye depends on two factors, drainage through the lacrimal passages and evaporation. Factors like decreased tear production, increased evaporation rate, tearfilm instability, tear hyperosmolarity, inflammations, ocular surface damages etc. can cause dryness to the eyes.[2]

TBUT test was first described by Norn MS, and then revised by Lemp and Holly.[3]

The conventional and most common TBUT measurement method is using slit lamp and sodium fluorescein. Noninvasive instruments (Oculus Keratograph 5M, Germany; K5) are used for automatic non-invasive tear breakup time (NIBUT) measurements.[4] In non-invasive procedure, a grid or concentric ring pattern is projected onto the cornea and the patient is asked to blink. The rings will appear distorted when the cornea becomes dry. Tearscope is a commercially available instrument used to measure NIBUT.[5]

  1. ^ Tsubota, Kazuo (1 November 2018). "Short Tear Film Breakup Time–Type Dry Eye". Investigative Ophthalmology & Visual Science. 59 (14): DES64–DES70. doi:10.1167/iovs.17-23746. ISSN 1552-5783. PMID 30481808.
  2. ^ Cite error: The named reference Kanski-DE was invoked but never defined (see the help page).
  3. ^ Myron, Yanoff; Jay S, Duker (16 December 2013). "Dry eye". Ophthalmology (4th ed.). Elsevier-Saunders. p. 277. ISBN 978-1-4557-3984-4.
  4. ^ Lan, Weizhong; Lin, Lixia; Yang, Xiao; Yu, Minbin (December 2014). "Automatic Noninvasive Tear Breakup Time (TBUT) and Conventional Fluorescent TBUT". Optometry and Vision Science. 91 (12): 1412–1418. doi:10.1097/OPX.0000000000000418. ISSN 1538-9235. PMID 25343685. S2CID 25165038.
  5. ^ David B., Elliott (2007). "Ocular health assessment". Clinical procedures in primary eye care (3rd ed.). Elsevier/Butterworth Heinemann. pp. 249–250. ISBN 9780750688963.