A TBUT time of less than what duration is considered abnormal?

The tear break-up time (TBUT) is a clinical test used to assess the stability of the tear film on the ocular surface. A shorter TBUT indicates that the tear film is unstable, which can lead to dry eye symptoms and ocular discomfort.

A TBUT time of less than 10 seconds is typically considered abnormal. When the tear film breaks up quickly—within this timeframe—it suggests inadequate tear production or rapid evaporation, both of which can contribute to dry eye disease. In contrast, a TBUT of 10 seconds or longer is generally associated with a more stable tear film, indicating better ocular surface health.

TBUT values serve as a critical indicator for clinicians diagnosing dry eye conditions or investigating potential underlying issues regarding tear film stability. A threshold of 10 seconds has been established in clinical practice, making it a standard metric referenced in various ophthalmic evaluations.