Comparison of Visual and Topographic Outcomes Between Deep Anterior Lamellar Keratoplasty and Corneal Allogenic Intrastromal Ring Segment Implantation in Advanced Keratoconus: A Preliminary Study

PURPOSE: To compare the visual, refractive, and topographic outcomes of deep anterior lamellar keratoplasty (DALK) and Corneal Allogenic Intrastromal Ring Segment (CAIRS) implantation in eyes with advanced keratoconus. METHODS: This retrospective comparative study included 52 eyes of 52 patients with advanced keratoconus (Kmax > 58.0 D along with poor contact lens tolerance and inadequate spectacle-corrected distance visual acuity) who underwent either DALK (n = 26) or CAIRS implantation (n = 26). Preoperative and postoperative uncorrected and best-corrected visual acuity (UCVA, BCVA), spherical equivalent, keratometric values, and corneal higher-order aberrations were analyzed. All patients completed a minimum follow-up of 6 months after CAIRS implantation or 6 months after suture removal after DALK. RESULTS: Both procedures resulted in significant improvements in UCVA, BCVA, spherical equivalent, and keratometric values (all P < 0.001). Postoperative BCVA was significantly better in the DALK group (P = 0.027), whereas postoperative UCVA, refractive parameters, and keratometric measurements were comparable between groups (all P > 0.05). No significant differences in postoperative aberration parameters were detected between groups. CONCLUSIONS: This study demonstrated that both CAIRS and DALK resulted in significant improvements in visual acuity, refractive outcomes, keratometric values, and aberrometric parameters in advanced keratoconus. CAIRS may have a role as an intermediate option in carefully selected cases before keratoplasty. Larger prospective studies with long-term follow-up are warranted.