Early Clinical Outcomes Of Femtosecond Laser-Assisted Corneal Allogenic Intrastromal Ring Segments (Cairs) For Corneal Ectasia: A Retrospective Study

To evaluate the clinical outcomes and surgical refinements of corneal allogenic intrastromal ring segments (CAIRS) in 20 eyes with corneal ectasia, with a 1-month follow-up.

This retrospective study was conducted in a specialized corneal surgery unit. All CAIRS procedures were performed using the Victus femtosecond laser for tunnel and segment creation. The first 6 cases followed the Istanbul nomogram, while the subsequent 14 cases used a customized nomogram developed by Lisa Fernández et al. with trefine-assisted implantation. Patients underwent standardized preoperative and postoperative assessments at 7 and 30 days.

This retrospective study analyzed 20 eyes with corneal ectasia treated with CAIRS using the Victus femtosecond laser for tunnel and segment creation. The first 6 cases (Grade III keratoconus) followed the Istanbul nomogram, with 20-minute dehydration, trypan blue staining, and a double-incision technique. Three cases required CAIRS removal due to overcorrection. The next 14 cases (Grade II-III keratoconus) followed a customized nomogram by Lisa Fernández et al., with 50% depth at a 6.0 mm optical zone, 10-minute dehydration at 35°C, and trefine-assisted implantation. Preoperative and postoperative evaluations at 7 and 30 days included visual acuity, refraction, corneal topography, and OT-SA

In the first 6 cases, 3 patients showed a Kmax reduction of 5.4D and gained 3.1±1.2 lines of visual acuity, but 3 experienced hyperopic overcorrection of 4.8D, requiring CAIRS removal. Mild structural damage at segment edges was noted.

In the subsequent 14 cases, using the adjusted technique, outcomes improved: SimK reduced by 4.2±2.3D, Kmax decreased by 5.1±2.7D, and visual acuity improved by 3.65±1.1 lines. No overcorrections occurred. Postoperative discomfort was mild and transient, resolving within 7 days. Trefine-assisted implantation preserved segment integrity, avoiding structural damage. The customized nomogram yielded more predictable refractive and topographic outcomes, improving safety and efficacy

Early results suggest that CAIRS effectively reduces corneal steepness and improves visual acuity in ectatic corneas. The initial technique, based on the Istanbul nomogram, led to overcorrection in some cases, requiring segment removal. Refinements including a customized nomogram (Lisa Fernández et al.), shallower implantation, reduced dehydration time, and trefine-assisted insertionyielded more predictable outcomes, better topographic stability, and improved safety. No structural alterations were observed with the modified technique, and all patients tolerated the procedure well, with only mild, transient discomfort. These findings support the refinement of nomograms and surgical techniques to optimize CAIRS implantation in corneal ectasia