[Multimodal evaluation of the ocular surface using a the new Lacrydiag device]

Dry eye disease is a very frequent condition with a significant impact on patients' quality of life. The most common clinical sign is fluorescein break up time (BUT). Recently, non-invasive measurement of BUT (NIBUT) by Placido disc analysis has been proposed to replace FBUT. We performed an automated NIBUT analysis using Lacrydiag and compared the values obtained with other typical dry eye criteria.

A retrospective study was carried out in the Bicêtre ophthalmology department from July 1 through October 30. Dry eye patients over 18 years of age with Oxford scores>1 and OSDI scores>22 were included. They underwent slit lamp examination to determine fluorescein BUT, Oxford and Arita MGD scores. On the same day, they were tested with the Lacrydiag to assess NIBUT, tear lake height and meibography. OSDI and Schirmer's testing were performed on the date of examination. In this study, only patients' right eyes were included. The correlation between NIBUT and OSDI, Schirmer's testing and tear lake height was analyzed by Pearson's test. The correlation between NIBUT and fluorescein BUT was analysed by both Pearson and Bland-Altman statistical tests.

Thirty right eyes (21 women, 9 men) were included. The mean age was 62.3 years (SD 16.0), mean OSDI 49.4 (SD=20.1), mean Oxford score 3.33 (SD 2.1), mean NIBUT 6.91sec (SD 3.4), and mean FBUT 3.6sec (SD 1.8). The NIBUT and FBUT were significantly correlated (R=0.139; P=0.042), with an even more significant concordance (r=0.55; P=0.001) on Bland-Altman graphic analysis, but the mean NIBUT was 2.7 seconds higher than the FBUT (P=0.001 on Bland-Altman analysis). In addition, NIBUT was correlated with the Oxford score (R=0.156; P=0.031), but not with Schirmer I score (R=0.120; P=0.061), OSDI score (R=0.018; P=0.48), tear lake height (R=0.04; P=0.148), or Arita meibomian gland dysfunction score (R=0; P=0.933).

NIBUT is a possible alternative to FBUT for the measurement of tear film stability, with the advantage of lack of dependence on the amount of fluorescein instilled. In addition, modern imaging methods allow for automated, and thus reproducible, measurement. However, its role in the diagnostic tool kit remains to be precisely defined, especially given its weak correlation with other markers of dry eye and its significant difference from FBUT. The definitive diagnosis of dry eye thus remains based on the combined analysis of signs and symptoms.