Tear Film Break-Up Time

The time required for a dry spot to appear on the corneal surface after blinking is referred to as the tear film break-up time (TFBUT).

Dry spots will appear as part of normal evaporation and diffusion of tears. In a normal healthy eye, dry spots start occuring between blinks at about 10-12 seconds, and an urge to blink is triggered.

When TFBUT is less than the blink rate, the ocular surface becomes unprotected, and the signs and symptoms of dry eye are exacerbated.