Ocular Surface Disease Parameters After Collagen Cross-Linking for Keratoconus

To analyze the variations in tear quantity and quality after corneal collagen cross-linking (CXL) in patients with keratoconus.

This is a prospective observational study of 24 eyes with keratoconus that underwent epithelium-off CXL. The variables studied were tear film osmolarity, subjective symptoms (Ocular Surface Disease Index), tear breakup time, Schirmer test (SCH) score, tear clearance, fluorescein staining, and lissamine green staining. Variables were determined preoperatively and 3, 6, and 12 months after CXL.

All the studied variables remained stable after 1-year follow-up (no significant difference in comparison with baseline values; Mann-Whitney U test). There was a positive paired correlation between the SCH score and tear clearance at 3; 0.532 (P < 0.01), 6; 0.434 (P = 0.04), and 12 months; 0.675 (P < 0.01). There was no correlation between the SCH score and tear breakup time, apart from a positive correlation at 12 months; 0.601 (P = 0.05). A negative correlation was found between osmolarity and the SCH score at 3; -0.589 (P < 0.01) and 12 months; -0.049 (P = 0.04). The Ocular Surface Disease Index did not correlate with any of the studied variables (Spearman test).

CXL, at least during the first postoperative year, does not modify the parameters currently used to evaluate tear film function. There is no correlation between objective and subjective parameters in the analysis of the tear film function.