Comparison of different methods to image the tear film before and during contact lens wear.

Purpose: To evaluate the repeatability and compare non-invasive tear breakup time (NIBUT) and tear film lipid layer thickness (TFLLT) measurements obtained using subjective (Keeler Tearscope-Plus) and objective (Oculus Keratograph 5M and LipiView II Interferometer) instruments before and during soft contact lens (CL) wear.

Methods: This prospective, randomised, double-masked, crossover study involved ten healthy participants who wore two types of daily disposable soft CLs: hydrogel and silicone hydrogel. NIBUT and TFLLT were assessed under pre cornea (before lens insertion) and pre lens (over the lens) conditions. NIBUT was measured using Tearscope-Plus and the Oculus Keratograph 5M, while TFLLT was assessed with Tearscope-Plus and the LifpiView II Interferometer. Repeatability was evaluated using repeated-measures ANOVA within-subject standard deviation (Sw), coefficient of repeatability (CR), and intraclass correlation coefficient (ICC). Correlation between instruments was assessed using Spearman coefficients, while agreement was evaluated using Bland-Altman analysis.

Results: NIBUT measured with the Tearscope-Plus demonstrated good to excellent repeatability (ICC: 0.84-0.96). TFLLT measured with the LipiView II Interferometer showed excellent repeatability (ICC: 0.92-0.96). The Oculus Keratograph 5M showed moderate to good repeatability for NIBUT (ICC: 0.67-0.85). No significant correlations were observed between NIBUT measurements from the Tearscope-Plus and Oculus Keratograph 5M (r range: 0.02-0.30; p > 0.05). In contrast, strong correlations were observed between TFLLT measurements from the Tearscope-Plus and LipiView II Interferometer in pre cornea (r = 0.72, p < 0.01) and pre hydrogel (r = 0.74, p = 0.02) conditions, with a moderate, non-significant correlation in the pre silicone hydrogel condition (r = 0.51, p = 0.13). Bland-Altman analysis revealed wide limits of agreement between instruments, indicating substantial measurements variability.

Conclusion: Tearscope-Plus and LipiView II Interferometer demonstrated high repeatability for NIBUT and TFLLT, respectively. However, the Tearscope-Plus overestimated both NIBUT and TFLLT values compared to objective instruments, indicating that these instruments should not be used interchangeably in clinical practice or research.