Extracorporeal Optimization of Corneal Allogenic Intrastromal Ring Segments (ECO-CAIRS) Using Ultra-high-Fluence Corneal Cross-linking

Purpose: To describe a new surgical technique to treat corneal allogenic ring segments (CAIRS) shaped by a femto-second laser with extracorporeal ultra-high-fluence corneal cross-linking (CXL) before insertion into the corneal stroma (ECO-CAIRS). Methods: Four eyes from four patients with stable keratoconus and maximum keratometry readings between 58.00 and 69.80 diopters (D) were analyzed. Each patient had a corneal thickness of at least 400 μm at 5 mm from the pupil center. CAIRS were prepared from donor corneas using a femtosecond laser. The segments were cross-linked with 30 and 60 J/cm 2 ultraviolet (UV) light fluences, and inserted without air-drying or extended dehydration. Results: Insertion was uneventful in all cases. CAIRS subjected to ultra–high-fluence CXL remained stiff during the entire insertion process and showed no tendency to soften. The initial ring segment thickness was approximately halved immediately after the high-fluence CXL treatment compared to pre-CXL levels; thickness levels increased within days after insertion. Conclusions: This new technique may provide multiple advantages over unmodified or air-dried CAIRS, including an easier insertion due to greater stiffness and resistance to re-swelling during insertion. The high UV fluences used should eliminate viable keratocytes, essentially transforming the segment into an acellular collagen scaffold. Finally, the marked transitory decrease in thickness may allow for the insertion of ring segments with greater overall volume, potentially increasing the corneal topographical effect. Further clinical research is required to assess the extent to which the effect on corneal topography is driven by the CAIRS volume and/or by its intrinsic stiffness.