Looking to improve the accuracy of fluorescein tear break-up time (TBUT) in diagnosing dry eye, new research suggests the longest fluorescein TBUT amongst three consecutive measurements might provide a more accurate assessment of tear film stability and disease severity compared to a single reading or the average of a few.

Researchers from China enrolled 147 participants who were about 38 years old. Testing included OSDI, corneal fluoresceine staining, Schirmer 1 and three consecutive fluorescein TBUT tests. The results of the latter were then placed into five different fluorescein TBUT categories: fluorescein TBUT max (the highest reading of the three), minimum fluorescein TBUT (the lowest reading of the three), the first fluorescein TBUT, the average of three fluorescein TBUTs and the average of the first and second fluorescein TBUT. The investigators found fluorescein TBUT max was obviously higher than the other four fluorescein TBUT values, while there wasn’t a significant difference among the other four.

Fluorescein TBUT max, which indicated a relatively full blink as well as a stable ocular environment between blink intervals, proved to be as reliable and effective as the average of the three readings, and superior to the minimum, first and the average of the first two values.

Additionally, fluorescein TBUT max also had the largest or the second largest AUROC in all three DED diagnostic criteria, while fluorescein TBUT min had the least.

Specifically, fluorescein TBUT max had a close correlation with OSDI, Schirmer I and corneal fluoresceine staining, which makes it an effective tool for a DED diagnosis, researchers said.

Previous studies have cast doubt on the reliability of FTBUT since the instillation of fluorescein fluid may reduce the stability of the tear film, the authors said. In order to eliminate the negative impact of fluorescein fluid, the researchers shook the wet sodium fluorescein stripe during the test to minimize the volume of fluid instilled into eyes and reduce the irritation of the ocular microenvironment.