Efficacy of intracorneal ring segments for treatment of residual astigmatism following penetrating keratoplasty: a systematic review and meta-analysis
Authors: Siddharth Nath 1, Alex Koziarz2, Mahshad Darvish-Zargar1, Julia Talajic3, Johanna Choremis1. 1McGill University, 2McMaster University, 3Université de Montréal.
Author Disclosures: S. Nath: None. A. Koziarz: None. M. Darvish-Zargar: None. J. Talajic: None. J. Choremis: None.
Abstract Body:
Purpose: Residual astigmatism following penetrating keratoplasty (PKP) represents a significant challenge. Although rigid gas permeable or scleral contact lenses can assist in correcting refractive error, post-PKP patients often suffer from contact lens intolerance, are at risk of graft failure from lens-induced neovascularization, and with prolonged use, face the specter of potentially devastating infectious keratitis. Failure of optical approaches often requires surgical intervention and there exist many options, including excimer laser ablation, wedge resection, relaxing incisions, and astigmatic keratotomy. All of these approaches, however, irreversibly alter the treated tissue, and, predicting the final refractive outcome is often difficult. To address these challenges, some surgeons have piloted the use of intracorneal ring segments (ICRSs) post-PKP to minimize residual astigmatism. ICRSs are commonly used to flatten the cornea in the setting of ectasia and there are established nomograms for predicting their refractive impact. Moreover, ICRSs have the benefit of being reversible and may be removed without permanent changes to the underlying tissue. The purpose of this study is to investigate the efficacy of ICRSs in the treatment of residual astigmatism post-PKP through a systematic review and meta-analysis.
Study Design: Systematic review and meta-analysis.
Methods: We searched five electronic databases, including Medline, Embase, and Web of Science, from inception until November 6, 2022, for studies evaluating the use of ICRSs for the treatment of residual astigmatism post-PKP. Our search was conducted without any language or study type restrictions, and we supplemented our database search with screening of the grey literature and hand searching of references of eligible studies. Our primary outcome was the change in refractive astigmatism post-ICRS placement. Secondary outcomes included the best-corrected distance visual acuity (BCVA), the maximum keratometry (Kmax), and the spherical error. We performed a pooled proportions meta-analysis for all outcomes and calculated a weighted mean difference and associated 95% confidence interval (CI).
Results: Six observational studies totalling 150 eyes fulfilled our inclusion criteria. The refractive astigmatism changed from 6.34 (0.35) to 3.67 (0.58) diopters following ICRS placement. Spherical error was reduced post-operatively to -1.87 (0.76) from a baseline of -4.43 (1.14) and Kmax was reduced from 52.30 (1.69) to 49.53 (2.26) diopters with ICRS insertion. BCVA improved post-procedure from a baseline of 0.53 (0.08) logMAR to 0.24 (0.03) logMAR. All changes were statistically significant (p<0.001).
Conclusions: ICRS insertion offers surgeons a reversible and efficacious option for the treatment of residual astigmatism post-PKP.
