Tear breakup time and the effect of lifting the eyelid during its measurement

Tear breakup time (TBUT) has, in general, been measured by scanning the cornea of subjects with vertical slits of various widths and without the use of yellow filters. Lid manipulations during the measurement of TBUT has been discouraged as it has been reported that lid manipulation causes a reduction in the TBUT value. In this study, the TBUTs and HTBUTs (TBUTs with the lid lifted up such that the palpebral aperture width was increased) of 36 Caucasian subjects were measured with the aid of a yellow filter (to enhance the contrast between the black spots or streaks formed and the fluorescein‐stained tears) and using a full‐aperture, circular beam for viewing the whole cornea instead of scanning with a vertical slit. The mean TBUT ± SD (of non‐contact lens wearers) measured was 10.1 ± 6.0 seconds. There was no significant difference between the TBUTs and HTBUTs for this group of subjects.