What is the most commonly utilized diagnostic measure of tear film stability?

• A. Tear film break up time (TFBUT)
• B. Schirmer tear test
• C. Corneal esthesiometry
• D. Tear osmolarity

Answer: (A)

Tear film stability is best judged by how long the tear film remains continuous after a blink. This is measured as tear film breakup time, typically using fluorescein to visualize the first spot where the tear film breaks up on the cornea. A longer breakup time reflects a more stable tear film, while a short time signals instability and potential dry-eye disease. It’s the most commonly used test because it directly assesses the dynamic property of the tear film, is quick and inexpensive, and provides actionable information about stability.

The other tests assess different aspects: the Schirmer test gauges tear production (volume) rather than stability; corneal esthesiometry measures corneal sensitivity; tear osmolarity reflects tear film composition and osmolar balance but not how rapidly the film breaks up.