Tear break-up time is the interval between a blink and the first appearance of dry spots on the corneal surface, indicating tear film stability. Shortened break-up time suggests evaporative dry eye.
Measurement
In the traditional test, fluorescein dye is instilled into the conjunctival sac, and the patient is asked to blink and then keep the eyes open while the tear film is observed under blue light. The time until the first dry area appears is measured in seconds.
- Values below a certain threshold indicate instability of the tear film
- Non-invasive methods using placido or interferometry patterns are also available
- Multiple measurements are often averaged for accuracy
- Environmental conditions and blink rate can influence results
Clinical Relevance
Tear break-up time helps diagnose and grade evaporative dry eye and meibomian gland dysfunction. It guides treatment aimed at improving tear quality and stability.
- Improvement after therapy reflects better surface lubrication
- Used alongside symptom questionnaires and structural lid assessment
- Changes correlate with visual fluctuations reported by patients
- Essential in both clinical practice and research settings
