Efficacy and safety of progressive fluence pulsed light epithelium-on accelerated corneal cross-linking for progressive keratoconus: 18-month prospective results

Aim: To report the 18-month clinical outcomes of the progressively higher fluence pulsed light (7.2 to 10 J/cm2) epithelium-on accelerated corneal crosslinking (PFPL M Epi-On ACXL) protocol for progressive keratoconus. Methods: This was a prospective, non-randomized interventional study. Fluence was assigned based on preoperative pachymetry: 7.2 J/cm2 (≤420 µm), 8.6 J/cm2 (420-459 µm), or 10 J/cm2 (≥460 µm). Riboflavin solutions (Paracel I and II), pulsed ultraviolet-A (UVA) irradiation (1s on/off), and consistent procedural timing (13min irradiation) were applied using the KXL I system. Uncorrected and best-corrected distance visual acuity (UDVA, CDVA), maximum keratometry (Kmax), higher-order aberrations (HOAs), and anterior segment optical coherence tomography (OCT) demarcation line depth were analyzed at baseline, 6, 12, and 18mo. Results: Totally 32 eyes of 32 patients aged over 26y with progressive keratoconus underwent PFPL M Epi-On ACXL were included. All groups demonstrated long-term stability in UDVA and CDVA. The 10 J/cm2 group showed the greatest improvement in CDVA (+0.17 decimal), significant corneal flattening (Kmax reduction: -1.03 D), and the most substantial HOAs reduction (-0.30 µm). No significant differences were observed between the 7.2 and 8.6 J/cm2 groups. OCT showed fluence-dependent demarcation line depths: 250±30 µm in the 10 J/cm2 group. No adverse events were observed. Concusion: PFPL M Epi-On ACXL appears to be a safe, repeatable, and effective long-term treatment for progressive keratoconus. The 10 J/cm2 fluence is associated with better optical and structural outcomes compared with lower fluences. Consistency in protocol application is essential to ensure efficacy.