Ferrara ring and the nomogram as the main strategy for correcting keratoconus: a systematic review of clinical findings

Abstract

Introduction: In the setting of corneal ectasias, keratoconus (KC) is a bilateral and asymmetrical disease that results in progressive thinning and tilting of the cornea, leading to irregular astigmatism and decreased visual acuity. The condition affects all ethnicities and both sexes. KC prevalence and incidence rates are close to between 0.2 and 4790 per 100,000 people and 1.5 and 25 cases per 100,000 person-years, respectively. For surgeons who implant Ferrara rings, the manufacturer has developed an online nomogram aimed at optimizing patient outcomes. Objective: The present study carried out a systematic review to present the main clinical outcomes of keratoconus treatment using the Ferrara ring. Methods: The systematic review rules of the PRISMA Platform were followed. The literature search was carried out from January to February 2023 in Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. Scientific articles from the last 15 years were selected. The quality of the studies was based on the GRADE instrument. The risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 60 articles were found, of which only 21 were part of this systematic review, after an eligibility analysis.It was concluded that the insertion of Ferrara rings in keratoconic eyes with previous cross-linking history using the company's nomogram results in significant improvements in visual, refractive, and tomographic results. Corneal densitometry in the anterior layer of the cornea decreases after the implantation of intrastromal corneal ring segments and correlates with corneal keratometry. Over 5 years, Ferrara-type intrastromal corneal ring segment implantation is a safe, effective, and stable procedure for restoring vision in pediatric patients with keratoconus old.