Correlation of Non-invasive Tear Break-Up Time with Tear Osmolarity and Other Invasive Tear Function Tests

Aim: To compare the outcomes of non-invasive break-up time (NI-BUT) test and the other conventional dry eye tests.Methods: The right eyes of 170 subjects were included in the study. In order to evaluate the tear quality of the patients, NI-BUT levels were measured by the Scheimplug-Placido disk system (Sirius topography). Tear osmolarity test was performed with TearLab Osmolarity System. Topical anesthesia-assisted type I Schirmer test and topical anesthesia-assisted BUT were lastly applied to all patients in order not to affect other measurements.Results: The mean NI-BUT value was 9.59 ± 4.37 sec, tear osmolarity was 292.93 ± 9.30 mOsm/L, Schirmer test was 15.32 ± 6.05 mm/5 min, and biomicroscopic BUT value was 8.98 ± 3.79 sec. The Schirmer test results were statistically significantly correlated with biomicroscopic BUT and NI-BUT values (p = .019, r = 0.180 and p = .030, r = 0.166; respectively). It was also found that tear osmolarity was strongly and inversely correlated with biomicroscopic BUT and topographic NI-BUT values (p < .001, r = -0.554 and p < .001, r = -0.528; respectively). There was no significant correlation between Schirmer test and tear osmolarity.Conclusion: It is important to use a sensitive, reproducible and non-invasive method in the evaluation of tear functions. We think that the objective and noninvasive topographic NI-BUT measurements and the minimally invasive osmolarity measurements should be used more frequently in practice because they are correlated with the measurements obtained by invasive methods and should be widespread in clinics.