Long-Term Structural And Functional Outcomes After Corneal Collagen Cross-Linking In Keratoconus Eyes Complicated By Central Toxic Keratopathy

To evaluate long-term visual, keratometric, and pachymetric outcomes in keratoconus eyes developing central toxic keratopathy (CTK) following corneal collagen cross-linking (CXL)

This retrospective study included 67 keratoconus eyes that developed CTK following epithelium-off CXL with iso-osmolar riboflavin performed between March 2019 and December 2025.

Uncorrected (UCVA) and best-corrected visual acuity (BCVA), maximum keratometry (Kmax), and thinnest pachymetry were assessed preoperatively and at final follow-up. Time-to-event analyses were conducted using Kaplan–Meier survival curves for BCVA deterioration (≥0.1 logMAR), Kmax progression (≥1.0 D), and pachymetry thinning (≥20 µm).

Mean age at CXL was 18.6±5.2 years, with male predominance (64.2%). Mean follow-up was 331±492 days (range 7–1682). In eyes with paired data, Kmax decreased significantly from 57.9±6.0 D to 53.5±5.4 D (mean Δ −4.43 D; 95% CI −5.79 to −3.08; p<0.001; Cohen’s dz=−1.11). Kmax flattening ≥1.0 D occurred in 86.1% of eyes, while progression ≥1.0 D occurred in 5.6%. Kaplan–Meier analysis demonstrated high Kmax progression-free survival through 2 years. Thinnest pachymetry decreased significantly (mean Δ −86.1 µm; p<0.001; dz=−1.74), with thinning ≥20 µm occurring early (median 161 days) and plateauing thereafter. BCVA remained stable overall, with approximately 70% of eyes maintaining BCVA without deterioration at one year.

In keratoconus eyes complicated by post-CXL CTK resulted in sustained keratometric flattening and biomechanical stabilization with preservation of visual acuity in majority. Pachymetric thinning occurred predominantly early and stabilized thereafter, consistent with stromal remodelling rather than ongoing ectatic progression.

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