Tear function and ocular surface changes following corneal collagen cross-linking treatment in keratoconus patients: 18-month results.

PURPOSE: To investigate the long-term effects that CXL has on the tear function and ocular surface in keratoconus. METHODS: Twenty-one consecutive patients (24 eyes) with progressive keratoconus scheduled for CXL were included. All patients underwent the following procedures: conjunctival impression cytology analysis, ocular surface disease index (OSDI) score, tear osmolarity test, Schirmer test, tear film breakup time (TBUT), ophthalmic surface fluorescein (Fl) staining, and topographical corneal evaluation before as well as 3 and 18 months after accelerated CXL. RESULTS: There was no change in the median OSDI score, tear osmolarity test, Schirmer test, and the Fl staining score after CXL. The median TBUT increased from 9.00 s at baseline to 12.00 s at 18 months postoperative (P < 0.001). The cytological features of the temporal and superior bulbar conjunctiva deteriorated at 3 months post-CXL (P < 0.001). An improvement in impression cytology analysis of the temporal conjunctiva was noted at 18-month follow-up (P < 0.001). Significant improvements in the median maximum keratometry and mean keratometry (K-mean) readings were also noted 18 months after CXL (P < 0.001). The changes in the K-mean correlated significantly with the changes in TBUT levels at 18-month follow-up as compared to baseline (r = - 0.688, P < 0.001). CONCLUSIONS: The improvement in TBUT, conjunctival squamous metaplasia, and the goblet cell density indicates a favorable effect of CXL on the ocular surface and tear film in keratoconus, presumably due to the reduced corneal irregularity after CXL.