Customised Peripheral Corneal Cross-linking (P-CXL) for Ultra-thin Corneas with Stage III and IV Keratoconus

This study aims to determine whether customised peripheral corneal cross-linking (P-CXL) can halt keratoconus progression in ultrathin corneas with stage 3 and 4 keratoconus, with thinnest pachymetry well below 400 μm and therefore excluded from most treatment protocols.

This retrospective study included 21 eyes with progressive keratoconus and thinnest pachymetry ranging from 97 to 399 μm (mean 315 μm), who underwent P-CXL between 2007 and 2020. The procedure involved preoperative NSAIDs therapy, tomography-guided customized epithelial debridement, the use of both hypo-osmolar and iso-osmolar riboflavin solutions, and 9.0 mW/cm² UV-A irradiation for 10 minutes. The outcome measures were best spectacle-corrected visual acuity (BSCVA), mean keratometry, maximum keratometry, and thinnest pachymetry.

After a minimum follow-up period of 12 months, P-CXL stabilized or improved mean keratometry and maximum keratometry in 85.7% of eyes (Kavg from 57.48 ± 9.38 to 56.43 ± 8.96 D, p < 0.001; Kmax from 72.77 ± 12.74 to 70.00 ± 11.50 D, p < 0.001), BSCVA in 90.5% of eyes (from 4.48 ± 2.85 to 5.72 ± 3.34 decimals, p < 0.001), and thinnest pachymetry in 81% of eyes (from 315.81 ± 90.05 to 342.33 ± 74.22 μm, p = 0.08). No adverse events and no loss of endothelial cell density occurred.

Customised peripheral corneal cross-linking (P-CXL) treated very severe keratoconus with a success rate of 85.7% and improved visual acuity and tomographic indicators in most cases. While a longer follow-up and a larger sample would help to support such conclusions to a greater extent, these results allow to broaden the treatment spectrum for patients with stage 3 and 4 keratoconus and contact lens tolerance.