Comparative analysis of tear film stability: Automated non-invasive and fluorescein tear break-up time

The tear film plays a crucial role in maintaining ocular surface physiology, with tear film stability being a key parameter. Tear break-up time (TBUT) is a common method for assessing tear film stability, involving the duration between a full blink and the initial disruption in the tear film. This study aimed to assess non-invasive break-up time (NIBUT) using an automatic approach and compare it with the traditional fluorescein break-up time (fBUT) method. Forty-three non- contact lens wearers were enrolled, and NIBUT data were collected using the Sirius+ instrument. fBUT was conducted using fluorescein sodium strips. Test-retest measurements were performed with 2 hours delay. NIBUT values were consistently longer than fBUT values (14.8 +/- 8.0 s vs. 8.7 +/- 5.2 s), aligning with existing literature. The results revealed good test-retest reliability for both methods; however, intraobserver repeatability was weak. A potential limitation was the non-randomized sequence of measurements, with fBUT consistently performed at the end due to its invasive nature. Variations in the coverage area of fBUT and NIBUT assessments, influenced by factors like the Placido disc dimension, and the lash shadows, may have contributed to shorter times with fBUT. Preliminary analyses focusing only on the corneal area covered by Sirius+ Placido rings supported this hypothesis. In summary, while NIBUT consistently showed longer values than fBUT, further investigations considering limitations and potential influencing factors are warranted for a comprehensive understanding of tear film stability assessment.