Analysis on the First Tear Film Break-up Point in Sjögren's Syndrome and non-Sjögren's Syndrome Dry Eye Patients

Background: ：Tear film instability plays an important role in the course of Sjögren's Syndrome dry eye (SSDE) even though it is generally classified as aqueous-deficient dry eye. The measurement of the first tear film break-up point (FTBUP) helps to evaluate the most unstable position of the tear film on ocular surface. We aim to investigate the first tear film break-up point (FTBUP) in Sjögren's Syndrome dry eye (SSDE) and non-Sjögren's Syndrome dry eye (NSSDE) patients, and explore its correlation with dry eye indices.Me thods Twenty-two SSDE patients (44 eyes) and 22 NSSDE patients (44 eyes) were enrolled in the study. Oculus Keratograph K5M was used to measure the FTBUP, the first and average non-invasive keratographic breakup time (f-NIKBUT and av-NIKBUT), and meibomian gland dropout. Other tests of tear film were also performed including Ocular Surface Dryness Index (OSDI), Schirmer I test, fluorescein break-up time and corneal fluorescein staining. One-way ANOVA with Bonferroni adjustment was used to compare dry eye indices. The locations of the FTBUP were compared between SSDE and NSSDE patients using chi-square test. The correlations between the FTBUP and ocular symptoms and signs were investigated using Pearson’s correlation coefficient test. Results: The FTBUP occurred at the supranasal quadrant in 12/88 eyes, supratemporal quadrant in 8/88 eyes, inferonasal quadrant in 34/88 eyes, and inferotemporal quadrant in 34/88 eyes. The percentage of the FTBUPs occurring at the inferior cornea was significantly higher in the SSDE group than in the NSSDE group (86.3% vs 68.1%, P=.042 ). Moreover, FTBUP was more frequently observed in the temporal area in SSDE patients with positive corneal fluorescein staining, as opposed to the nasal area in SSDE patients with negative corneal staining( P=.032 ). Conclusion: Tear film was more unstable in the inferior cornea than other areas of cornea in both SSDE and NSSDE patients. The location of the FTBUP in SSDE patients had a close relationship with cornea fluorescein staining.