A Manual Technique For Corneal Allogeneic Intrastromal Ring Segments (Cairs) Without Femtosecond Laser

To evaluate the outcomes of corneal allogeneic intrastromal ring segments (CAIRS) using a simplified manual technique for treating keratoconus.

This study was approved by Nihon university and Kikuna Yuda Eye Clinic.

Surgeries were performed under local anesthesia by a single surgeon. An intrastromal pocket for donor tissue implantation was manually created using a spatula, and donor corneas were prepared using a Jacobs CAIRS trephine. Corneal parameters, including higher-order aberrations (HOAs), coma, and spherical aberrations (SAs) at a 6 mm diameter, were measured using optical coherence tomography (CASIA SS-1000, Tomey, Japan). Anterior and posterior corneal indices, subjective refractive power, cylinder, spherical equivalent, and best-corrected visual acuity. Intra- and postoperative complications were also analyzed.

This prospective case series included five eyes from five patients with keratoconus (4 males, 1 female, mean age 32.5 ± 10.6 years) treated with manual CAIRS. Over a mean follow-up of 6.4 ± 2.9 months, no complications occurred. BCVA improved from 0.74 ± 0.44 logMAR preoperatively to 0.19 ± 0.66 logMAR (p = 0.043). The maximum keratometry (Kmax) value decreased from 63.6 ± 8.3D preoperatively to 59.6 ± 6.8D postoperatively (p = 0.043). Spherical Equivalent improved from -11.2 ± 5.8D to -5.3 ± 3.1D (p = 0.043), and astigmatism reduced from -5.0 ± 3.4D to -3.3 ± 2.9D. Total corneal HOAs decreased from 5.6 ± 1.6μm to 4.2 ± 1.6μm postoperatively (p = 0.043).

We have developed a simple and cost-effective manual technique for CAIRS. Further comparative studies with larger sample sizes are warranted to validate its efficacy and refine the technique.