Correlation between central stromal demarcation line depth and changes in K values after corneal cross-linking (CXL)

PURPOSE: A stromal demarcation line (DL) after corneal cross-linking (CXL) has lately been suggested as a surrogate parameter for the success of CXL. The aim of this study was to investigate the correlation between depth of the central DL 1 month and the change in K values 12 months after CXL. METHODS: Treatment-naive subjects with keratoconus were treated using an accelerated CXL protocol [A-CXL(9*10)]. Depth of the DL/relative depth of the DL (DL%) was measured using Visante OCT imaging 1 month postoperatively (OP). K(max)/K(2.5) (preOP) and change in K(max)/K(2.5) (preOP − 12 months postOP) were assessed using corneal tomography (Pentacam HR, Oculus GmBH). RESULTS: Forty eyes were treated following the A-CXL(9*10). The mean DL depth was 200 ± 99 μm (range 71 to 479)/mean DL% = 42.70 ± 20.00% (range 17–90). There was no statistically significant correlation between stromal depth of the DL and change in K(max) or K(2.5), respectively (Spearman rho DL/∆K(max) − 0.14 and DL/∆K(2.5) − 0.14). Between DL% and the changes in maximum K values or K(2.5), no statistically significant correlation was found as well (Spearman rho DL%/∆K(max) − 0.10 and DL%/∆K(2.5) − 0.19). Mean change in K(max) after 12 months was − 0.68 ± 2.26 diopters (D) (median − 0.35 D) and − 0.82 ± 1.6 D (median − 0.65 D) for K(2.5) (p = 0.07; p = 0.02). CONCLUSIONS: No statistically significant correlation was found between the stromal central depth of the DL and any outcome parameter for CXL after 12 months. Therefore, the interpretation of the DL as a predictive parameter for the effect of the procedure may not apply.