The Impact On Keratometric Values Following Corneal Allogeneic Intrastromal Ring Segments (Cairs) Using A Simplified Manual Technique

To evaluate the changes in visual acuity keratometric values and corneal higher-order aberrations (HOAs) following corneal allogeneic intrastromal ring segmentation (CAIRS) using a simplified manual technique for the treatment of keratoconus.

This was a retrospective study conducted at Nihon University Itabashi Hospital, and Kikuna Yuda Eyeclinic registered from January 2024 to December 2024 at Nihon University or Kikuna Yuda Eye Clinic.

All CAIRS procedures were performed by a single surgeon. Corrected distance visual acuity(CDVA), measured as the logarithm of the minimum angle of resolution, and corneal parameters were evaluated before and after the surgery. In addition tokeratometric values, corneal wavefront aberrations were assessed using anterior segment optical coherence tomography (ASOCT, CASIA2; Tomey). Total HOAs, coma, and spherical aberration from the anterior corneal surface, posterior corneal surface and total cornea were analyzed. Changes from preoperative to postoperative measurements were analyzed using the Wilcoxon signed-rank test, and Spearman’s correlation coefficients were calculated to assess the relationship between each parameter and graft size.

This study included 28 eyes of 27 patients (23 men, 4 women; mean age 34.4±12.2 years). No complications were observed over a mean follow-up period of 6.2 ± 6.0 months. Postoperative CDVA (0.21 ± 0.28) showed significant improvement compared to the preoperative value of 0.55 ± 0.60 (p < 0.001). The maximum keratometry (Kmax) value decreased from 63.27 ± 12.64 D preoperatively to 60.68 ± 11.04 D postoperatively (p = 0.037). In the anterior cornea, total HOAS, coma, and SA changed significantly: two decreased (log Coma-like: P = 0.001, log HOAs: P = 0.026), while one increased (log Spherical-like: P < 0.001). No significant changes were observed in HOAs for the posterior or total cornea. Graft size negatively affected cylinder (P = 0.047)

CAIRS showed significant improvement in BCVA, various K-values, whereas concerns may exist about the effect on total HOAs due to negative impact on posterior surface. The development of a better nomogram may be required.