Correlation of Demarcation Line Depth With Medium-Term Efficacy of Different Corneal Collagen Cross-Linking Protocols in Keratoconus

摘要

Purpose: To compare demarcation line depth (DD) and topographic changes among different corneal collagen cross-linking (CXL) protocols and to evaluate the relation of DD with medium-term efficacy of CXL in halting progression of keratoconus. Methods: The study included 124 patients (mean age 19 +/- 4.8 years) with progressive keratoconus who underwent conventional (3 mW/cm(2)/30 min), accelerated (18 mW/cm(2)/5 min), or transepithelial (TE) CXL (3 mW/cm(2)/30 min) and followed up for at least 2 years. Baseline and final corneal topographic parameters and DD determined with anterior segment optical coherence tomography 1 month after CXL were compared among the protocols and the correlation between DD and topographic changes at the end of 24 months was analyzed. P 0.05 was considered as statistically significant. Results: Mean DD was significantly higher in the conventional and accelerated groups (335.19 +/- 71.13 mu m and 304.97 +/- 94.45 mu m, respectively) compared with the TE group (239.92 +/- 71.37 mu m) (P 0.001). After conventional and TE CXL, keratometric parameters improved remarkably, whereas accelerated CXL only lowered K1 and Kmax (P 0.05). No correlation was found between DD and topographic changes (P 0.05). Progression was detected in 3 eyes in the conventional group (4.1%), 3 in the accelerated group (7.7%), and none in the TE group. The use of either riboflavin D or M made no differences in terms of DD and topographic parameters (P 0.05). Conclusions: In conventional and accelerated protocols, corneal stromal demarcation line is deeper compared with TE CXL; however, the DD has no correlation with topographic changes, which means that DD is not a direct measure for the efficacy of CXL.