Visual and Topographic Outcomes After Corneal Allogeneic Intrastromal Ring Segments for Keratoconus: A Systematic Review and Meta-Analysis.

PURPOSE: Corneal allogeneic intrastromal ring segments (CAIRS) are a novel therapeutic approach to treat ectatic diseases such as keratoconus and improve visual acuity as well as corneal topography. This analysis aimed to evaluate the visual outcomes and corneal topography changes after CAIRS implantation for keratoconus.

DESIGN

Systematic Review and Meta-Analysis.

METHODS

In this systematic literature review and meta-analysis (ID: CRD42024612508) original peer-reviewed clinical studies on the effect of CAIRS in eyes with keratoconus were included. Exclusion criteria were preimplanted ring segments, ectatic diseases other than keratoconus, as well as no reported pre- or postoperative outcome parameters. Cochrane, Embase, PubMed and Web of Science libraries were screened in November 2024 by 2 researchers independently. The risk of bias was assessed using the Evidence Project risk of bias tool. The primary effect measure was the difference in corrected distance visual acuity (CDVA) before and after CAIRS. Additionally, changes in uncorrected distance visual acuity (UDVA), spherical equivalent (SE), cylinder, flat keratometry, steep keratometry, maximum keratometry (Kmax), mean keratometry, thinnest corneal thickness, and higher order aberrations (HOAs) after CAIRS were analyzed and compared using a random effects model. In addition, postoperative complications were documented.

RESULTS

Fourteen clinical studies with a total of 442 eyes were included in the meta-analysis. The mean improvement in CDVA was 0.37 logMAR (95% CI: 0.28, 0.46; 14 studies; n = 442 eyes). UDVA improved by 0.43 logMAR (95% CI: 0.34, 0.55; 11 studies; n = 427 eyes). SE improved by 4.59 D (95% CI: 3.35, 5.84; 12 studies; n = 430 eyes). Kmax was reduced by -4.49 D (95% CI: -6.05, -2.92; 13 studies; n = 439 eyes) and total HOAs decreased by -0.33 µm (95% CI: -0.62, -0.03; 6 studies; n = 171 eyes). One severe adverse event (0.2%) reported was an acute rejection, which necessitated explantation.

CONCLUSIONS

This meta-analysis demonstrates that CAIRS transplantation is an effective procedure that can significantly improve UDVA, CDVA, and topographic outcomes in keratoconus eyes with low complication rates.