Reliability and Agreement of Subjective and Objective Non-Invasive Break-Up Time Measurements in Contact Lens Wearers.

Purpose: To assess the reliability and agreement of non-invasive break-up time (NIBUT) in symptomatic and asymptomatic contact lens (CL) wearers using automatic objective and conventional subjective techniques.Methods: In this prospective cross-sectional study, soft CL wearers, classified into symptomatic and asymptomatic based on the Contact Lens Dry Eye Questionnaire-8, underwent NIBUT assessment with the CL in situ. The CA-800 Corneal Analyzer and the EasyTear (R) VIEW+ Tearscope were used for objective and subjective evaluation, respectively. The within-subject repeatability and intraclass correlation coefficient (ICC) were calculated. The agreement between the devices was compared using the Bland-Altman method.Results: A total of 141 CL wearers (51 male and 90 female) with a mean age of 33.6 (SD = 12.2) years were included. The repeatability and ICC values obtained with the CA-800 device when measuring NIBUT were 5.4 s and 58.6% across the whole sample, 4.2 s and 48.8% for the asymptomatic group and 7.1 s and 68.4% for the symptomatic group. When using the subjective method (EasyTear (R)), the respective repeatability and ICC values were 7.3 s and 32.7% for the whole sample, 6.5 s and 30.4% for the asymptomatic group and 8.6 s and 35.9% for the symptomatic group. The CA-800 device provided significantly (p < 0.001) shorter NIBUT values compared with EasyTear (R) for the whole sample (3.3 [2.9] vs. 8.1 [3.4] s), the asymptomatic (3.3 [3.0] vs. 7.7 [3.6] s) and the symptomatic (3.8 [2.9] vs. 8.6 [3.0] s) groups.Conclusion: Objective (CA-800) NIBUT assessment provides more reliable measurements than the conventional subjective technique using the EasyTear (R) device. However, CL practitioners should also be aware that the objective method indicates shorter NIBUT values. Symptomatic CL wearers may also need a higher number of NIBUT measurements to obtain reliable estimations.