title: Tomographic Findings After Implantation of Ferrara Intrastromal Corneal Ring Segments in Keratoconus.
abstract: OBJECTIVE
  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.].
authors.forename: João Marcelo
authors.initials: JM
authors.lastname: Lyra
authors.forename: Daniela
authors.initials: D
authors.lastname: Lyra
authors.forename: Guilherme
authors.initials: G
authors.lastname: Ribeiro
authors.forename: Leonardo
authors.initials: L
authors.lastname: Torquetti
authors.forename: Paulo
authors.initials: P
authors.lastname: Ferrara
authors.forename: Aydano
authors.initials: A
authors.lastname: Machado
mesh_terms: D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D003315:Cornea / Q000503:physiopathology; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019904:Polymethyl Methacrylate; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D012189:Retrospective Studies; D014054:Tomography; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
chemical_list: D019904:Polymethyl Methacrylate