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From the February 2017 issue of Journal of Refractive Surgery, the highest ranked journal in the refractive surgery subspecialty by impact factor. (Editor-in-Chief: J. Bradley Randleman, MD)
Tomographic Findings After Implantation of Ferrara Intrastromal Corneal Ring Segments in Keratoconus
By João Marcelo Lyra, MD, PhD; Daniela Lyra, MD; Guilherme Ribeiro, MD; Leonardo Torquetti, PhD; Paulo Ferrara, PhD; Aydano Machado, MD, PhD
PURPOSE: To analyze and compare changes to the anterior and posterior corneal surfaces after Ferrara intracorneal ring segment (ICRS) (AJL, Boecillo, Spain) implantation and to correlate those changes with visual outcomes.
METHODS: This retrospective case series study comprised consecutive patients with keratoconus implanted with the Ferrara ICRS. Computed tomography scans of the two corneal surfaces were obtained preoperatively and postoperatively with a rotating Scheimpflug imaging system. The Wilcoxon test was used to compare groups, and the Pearson's correlation coefficient was used to measure the strength of the correlation between variables.
RESULTS: The study evaluated 241 eyes in 182 patients with keratoconus. Both corneal surfaces showed statistically significant decreases in average steep keratometry (K2) values, corneal astigmatism, elevation at the apex and at the thinnest point, maximum elevation in the central 4-mm area, and elevation inside the 3- and 4-mm zones and at the 3-mm ring. Regarding anterior surface parameters, a significant decrease was observed in flat keratometry (K1), whereas asphericity increased. On the posterior corneal surface, no significant changes in K1 and asphericity were observed. Poor correlation was found between visual outcomes and changes in tomographic parameters. The best correlation was obtained for anterior corneal astigmatism.
CONCLUSIONS: ICRS implantation led to statistically significant changes in both anterior and posterior corneal surfaces. However, correlation between visual outcomes and tomographic parameters was poor.
[J Refract Surg. 2017;33(2):110–115.]
From the Brazilian Study Group of Artificial Intelligence on Ocular Solutions, Maceió, Brazil (JML, DL, GR, LT, PF, AM); Paulo Ferrara Eye Clinic, Belo Horizonte, Brazil (LT, PF); Centro de Excelência em Oftalmologia, Pará de Minas, Brazil (LT); Universidade Federal de Alagoas, Maceió, Brazil (DL, GR, AM); and Universidade Estadual de Ciências da Saúde de Alagoas, Maceió, Brazil (JML). Dr. Ferrara has a proprietary interest in the Ferrara ring. The remaining authors have no financial or proprietary interest in the materials presented herein.
Study concept and design (JML, DL, GR, LT, PF, AM); data collection (JML, DL, GR, LT, PF, AM); analysis and interpretation of data (JML, GR, LT, PF, AM); writing the manuscript (JML, DL, GR, LT, PF, AM); critical revision of the manuscript (JML, DL, GR, LT, PF, AM); statistical expertise (JML, GR); administrative, technical, or material support (JML, GR, LT, PF); supervision (JML, GR, LT, PF)
Correspondence: João Marcelo Lyra, MD, PhD, Rua Desembargador Tenório, 80, Maceió 57050-050, Brazil. E-mail: firstname.lastname@example.org
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