Outcomes of Accelerated Corneal Cross-linking With Hypo-osmolar Riboflavin in Corneas Thinner Than 400 µm: A Comparative Study Based on Intraoperative Corneal Thickness

Purpose: To evaluate the safety and efficacy of accelerated corneal cross-linking (A-CXL) using hypo-osmolar riboflavin solution (HRS) in patients with keratoconus and corneal thickness (CT) thinner than 400 µm and compare outcomes based on intraoperative CT. Methods: This retrospective, non-randomized study included 76 eyes of 69 patients with progressive keratoconus who underwent A-CXL using HRS. Patients were divided into two groups based on intraoperative CT: thinner than 400 µm and 400 µm or thicker. Endothelial cell density (ECD), visual acuity, refractive outcomes, topographic parameters, and higher order aberrations (HOAs) were assessed preoperatively and postoperatively at 3, 6, and 12 months. Results: No significant ECD reduction was observed in either group at 12 months ( P = .504, P = .695). Visual acuity improved significantly in both groups (each P < .05) without intergroup differences (uncorrected: P = .797, corrected: P = .301). Thinnest CT increased significantly from month 3 to 12 in both groups (each P < .05). The thinner than 400 µm group showed a significant reduction in maximum keratometry ( P = .014), whereas the 400 µm or thicker group remained stable ( P = .064). HOAs did not change significantly in both groups (each P > .05). Permanent corneal haze (grade 1 in two patients, grade 2 in two patients) developed in four patients (two per group); none required corneal transplantation. Conclusions: A-CXL using HRS appears to be a safe and effective treatment for progressive keratoconus in thin corneas, preserving endothelial integrity. Comparable visual and topographic outcomes suggest that A-CXL remains effective even when intraoperative CT remains thinner than 400 µm.