Dehydration and Rehydration Behavior of Ultra-High-Fluence Extracorporeal Cross-Linked Corneal Allogenic Intrastromal Ring Segments (ECO-CAIRS)

PURPOSE: To evaluate the effects of extracorporeal ultra-high-fluence corneal cross-linking (ECO-CAIRS) on the dehydration and rehydration behavior of porcine corneal stromal ring segments in an experimental model simulating the preparation of corneal allogenic intrastromal ring segments. SETTING: ELZA Institute, Zurich, Switzerland. METHODS: Corneal ring segments (two per cornea) were prepared from freshly enucleated porcine corneas (n=48) and randomly divided into three groups: controls (no CXL, Jerky technique), extracorporeal ultra-high-fluence CXL at 30 J/cm2, and 60 J/cm2 (n=32 each). After epithelial removal and ring preparation, segments in the control group were soaked in balanced salt solution (BSS), while those in the experimental groups were soaked in riboflavin solution (Ribo-Ker, EMAGine AG, Zug, Switzerland) for 10 minutes. Each group subsequently underwent a total dehydration period of 45 minutes, which included both UV-A irradiation and waiting phases for the CXL-treated groups, followed by a 10-minute rehydration phase using BSS. Segment thickness was measured by calibrated imaging at baseline, after dehydration, and after rehydration. RESULTS: Baseline structural thickness values did not differ significantly between groups. Both CXL-treated groups demonstrated significantly greater dehydration (p<0.01) and reduced rehydration (p<0.01) when compared to controls. No significant differences were found between the two CXL-treated groups. Ultra-high-fluence cross-linking enhanced segment dehydration and slowed rehydration. CONCLUSIONS: ECO-CAIRS effectively modulates the dehydration and rehydration of corneal ring segments, which may improve handling and implantation characteristics during surgery. These findings support the potential clinical benefit of CXL in CAIRS procedures. Further in vivo studies are required to confirm long-term behavior and biomechanical impact.