Clinical improvement of ocular surface parameters in dry eye patients following treatment with urea/crosslinked-hyaluronate eyedrops correlates with the secretion of MUC-4

Objectives: To assess the ocular surface status after treatment with urea/crosslinked hyaluronate (U-HACL) tear substitute in dry eye (DE) patients. Methods: Seventeen DE patients were included in the study. They instilled U-HACL drops three times/day for 2 months. Symptoms (by OSDI and VAS), osmolarity, tear film (through Schirmer and tear film breakup time), corneal and conjunctival damage (with NEI and van Bijsterveld scores), impression cytology (number of PAS positive cells and MUC-4 immunostaining), and tear sampling were analyzed pre- and post-treatment. Results: After the treatment, there was a significant improvement of VAS (7.16 +/- 2.59 vs. 3.94 +/- 2.23), OSDI (56.96 +/- 25.97 vs. 29.94 +/- 20.15), Schirmer (8.22 +/- 6.86 vs. 10.66 +/- 6.92), TFBUT (3.16 +/- 2.28 vs. 5.55 +/- 2.47), NEI (7.16 +/- 2.50 vs. 2.88 +/- 2.80), and van Bijsterveld (10.27 +/- 4.25 vs. 6.5 +/- 3.79) score, p < 0.01. There was a significant increase of PAS positive cells and MUC-4 (respectively, 44.21 +/- 14.8 vs. 67.0 +/- 10.1 and 49.79 +/- 20.0 vs. 75.9 +/- 20.7), p < 0.01. Conclusion: The rise of MUC-4 expression probably contributed to the increase in ocular wettability and amelioration of clinical parameters following the administration of U-HACL eye drops.