Tear Breakup Time (TBUT) is a vital test for assessing tear film stability and diagnosing dry eye disease. Understanding TBUT can lead to better eye health.
Tear breakup time (TBUT) is a simple clinical test used to evaluate the stability of your tear film. It plays a crucial role in diagnosing evaporative dry eye disease. Understanding TBUT is important because it helps our eye doctors determine if your eyes are properly lubricated and protected.
Tear breakup time (TBUT) measures the interval between your last blink and the moment when the first dry spot appears on the eye’s surface. This test is conducted after instilling a small amount of fluorescein dye into your tear film so that any disruptions in the tear layer become visible under a cobalt blue light during a slit lamp examination.
A normal TBUT is typically greater than 10 seconds. When the recorded TBUT is under 10 seconds, it indicates that the tear film may be breaking up too quickly, suggesting tear instability and possibly dry eye disease. In some cases, patients with a low TBUT may also show punctate epithelial erosions (PEE) that stain positively with fluorescein—another sign of ocular surface dryness.
Your tear film is essential for keeping your eyes both comfortable and protected. It serves as a natural lubricant, assists in clearing the ocular surface, and provides a smooth optical surface that contributes to clear vision. Here’s why TBUT is so significant:
If you experience dry eye symptoms, consult an eye doctor to discuss TBUT testing and improve your ocular comfort.
During a TBUT test, our eye doctors carry out a number of simple steps. First, they place a small amount of fluorescein dye onto your eye, which mixes with your tear film. You are then asked to blink a few times so the dye can spread evenly across your ocular surface. Once the dye has been distributed, you are asked to keep your eyes open while the doctor observes them under a cobalt blue light using a slit lamp.
The doctor watches for the first dark spot—or “breakup”—to appear in the otherwise fluorescent tear film. The exact time from your last blink until this dry spot appears is recorded in seconds, and this value is your TBUT. A value under 10 seconds suggests that your tears are evaporating too rapidly, a key marker when diagnosing dry eye disease.
Fluorescein dye plays an important role in the TBUT test because of its ability to highlight the tear film. When exposed to cobalt blue light, the dye emits a bright fluorescence that makes it easy for the examiner to see any gaps or dry areas that develop in the tear film. This method, while invasive due to the dye instillation, remains one of the most straightforward ways of assessing tear film stability.
This approach is favored in many clinical settings because it provides immediate and visible evidence of tear film break-up, thereby helping our eye doctors make informed decisions about the presence and severity of dry eye symptoms quickly.
If you experience dry eye symptoms, consult an eye doctor to discuss TBUT testing and improve your ocular comfort.
Tear breakup time (TBUT) measures tear film stability, crucial for diagnosing dry eye disease. Learn more about this essential test.
