Fluorescein tear breakup time predicts pre-lens tear film stability and contact lens comfort

Background: Soft contact lenses divide tear film into pre-lens and post-lens layers. This study evaluated whether pre-lens tear film stability, assessed by fluorescein tear breakup time (TBUT) and noninvasive keratograph breakup time (NIKBUT), predicts subjective comfort. Methods: This single-center prospective study recruited participants aged 20–40 years without ocular diseases. Narafilcon A and verofilcon A contact lenses were used in a crossover design, with participants assigned to wear narafilcon A lenses for one week followed by verofilcon A lenses for another week (Group NV), or the reverse sequence (Group VN). Pre-lens tear film stability was assessed by NIKBUT and fluorescein TBUT on day 1 and day 7. These ocular measurements were correlated with subjective comfort evaluated with Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8) after wearing each lens type. Results: A total of 82 participants (mean age 29.3 ± 3.3 years; 84% female) completed the study. CLDEQ-8 scores were lower with verofilcon A than with narafilcon A (7.09 ± 5.92 vs. 10.21 ± 7.23; p < 0.05). Fluorescein TBUT was consistently longer with verofilcon A than with narafilcon A, both at 15 minutes on day 1 (Group NV: 6.04 vs. 3.80 seconds; Group VN: 7.24 vs. 3.25 seconds) and at 6 hours on day 7 (Group NV: 4.87 vs. 3.03 seconds; Group VN: 5.67 vs. 3.15 seconds). NIKBUT did not differ significantly between the two lenses at either time point. CLDEQ-8 scores negatively correlated with fluorescein TBUT for both lens types (ρ = –0.29 for narafilcon A, p = 0.002; ρ = –0.20 for verofilcon A, p = 0.008). Conclusion: Verofilcon A provided better subjective comfort compared with Narafilcon A. Fluorescein TBUT, but not NIKBUT, may serve as a complementary assessment for pre-lens tear film stability and subjective comfort, suggesting that fluorescein TBUT offers distinct clinical value in contact lens practice.