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

Abstract

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.