Stromal Demarcation Line Depth As A Predictor Of 12-Month Tomographic Stabilization After Corneal Cross-Linking

To evaluate whether stromal demarcation line (DL) depth predicts 12-month tomographic response after corneal cross-linking (CXL) in progressive keratoconus. We aimed to determine whether absolute and relative DL depth correlate with change in maximum keratometry (ΔKmax), and whether DL depth differs between accelerated and sub-400 epithelium-off protocols.

Single-center prospective study conducted in a tertiary ophthalmology referral center specializing in corneal diseases and keratoconus management.

Eighty-seven eyes with progressive keratoconus underwent accelerated epithelium-off CXL or sub-400 epithelium-off CXL. At 1 month, anterior segment OCT was used to measure absolute DL depth (µm) and relative depth (DL%) based on local pachymetry. Tomographic response was assessed by change in Kmax at 12 months. Intergroup comparisons were performed using the Mann–Whitney test. Correlations were analyzed using Spearman’s coefficient.

A visible DL was identified in 56 eyes. Mean DL depth was approximately 225 µm (~50% stromal thickness). Accelerated CXL produced significantly deeper DL compared with the sub-400 protocol (p<0.001). At 12 months (n=53), mean ΔKmax was –0.52 D, with an overall stabilization rate of 87%. A significant negative correlation was observed between DL depth and ΔKmax (rho ≈ –0.6; p<0.01). Similar findings were observed for DL%.

Deeper stromal demarcation line depth, expressed in absolute and relative values, was significantly associated with improved 12-month tomographic outcomes. These findings suggest that DL depth may represent an early surrogate marker of biomechanical efficacy after CXL rather than solely reflecting photochemical penetration. DL assessment could contribute to early postoperative evaluation of treatment effectiveness.