Femtosecond Laser Created Corneal Allogenic Intrastromal Ring Segments (Cairs).

CAIRS is an emerging treatment option which involves the insertion of arc-shaped donor corneal tissue into the corneal stroma of ectatic eyes, resulting in reduced irregular astigmatism, flattening of the cornea, and reduced higher order aberrations. This procedure is capable of providing significantly improved visual quality while circumventing many of the problematic complications often seen with ICRS, and without the need for tissue ablation as in topography-guided PTK. This study reports on the outcomes CAIRS in eyes with keratoconus and post-LASIK ectasia, where both the CAIRS segment and the recipient channel are created using femotosecond laser. 

Private Ophthalmology clinic, Brisbane, Australia.

CAIRS surgery was performed on one eye of patients with diagnosed keratoconus or post-LASIK ectasia. Allogenic ring segments were created using two anterior lamellar keratoplasty profiles of different depth and diameter on a donor cornea using the Alcon Wavelight FS200 Femtosecond laser. The segment was then manually inserted into a channel which was created in the recipient cornea using the FS200, at a depth of 50-60% of the corneal thickness. At 3 months post-op, UDVA, CDVA, Subjective refraction, and corneal tomography were measured.

A total of 26 eyes underwent CAIRS between March 2021 and July 2023. Mean follow-up time was 112 ± 44 days. On average, KMax decreased by 3.9 ± 4.3D, with a maximum flattening of 18.6D. Spherical equivalent reduced by 3.61 ± 5.30D, and cylinder by 1.92 ± 2.86D. The maximum reduction in refractive cylinder was 9.50D. CDVA improved by an average of 0.2 ± 0.2 logMAR, and UDVA by 0.4 ± 0.3 logMAR. The maximum improvements in CDVA and UDVA were 0.7 logMAR and 1.1 logMAR, respectively. No significant complications were recorded.

CAIRS is a safe and effective procedure for the treatment of keratoconus capable of significant corneal flattening, reduced refractive cylinder, and improved visual acuity. The authors recommend using femotosecond laser for highly accurate and reproducible segment creation. The method of treatment planning used for segment arc length and positioning is showing promising results and is in the process of being further validated with a larger sample and longer follow-up.