title: Inferior intrastromal corneal ring segments in paracentral keratoconus with no coincident topographic and coma axis.
abstract: OBJECTIVE
  To assess the visual and refractive outcomes of implantation of intrastromal corneal ring segments (ICRS) in keratoconic eyes with no coincident topographic and comatic axes.
  
  
  METHODS
  Forty-one keratoconic eyes of 39 patients with no coincident topographic and comatic axes were implanted inferiorly with a Ferrara-type ICRS (Keraring SI6; Mediphacos Inc., Belo Horizonte, Brazil) of 150° of arc with a thickness of 150, 200, and 250 μm. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal coma-like root mean square, and residual refractive errors analyzed using vector analysis were recorded before and 6 months after the ICRS implantation.
  
  
  RESULTS
  Mean UDVA was 0.76 ± 0.41 logMAR before and 0.53 ± 0.46 logMAR after surgery (P = .0006). CDVA was 0.13 ± 0.14 logMAR before and 0.07 ± 0.09 logMAR after surgery (P = .0007). Two eyes (4.9%) lost two lines or more of CDVA, 3 eyes (7.32%) lost one line, 16 eyes (39.02%) had no change in CDVA, 9 eyes (21.95%) gained one line, and 11 eyes (26.83%) gained two lines or more of CDVA. The safety index was 1.10. Spherical equivalent was significantly reduced after ICRS implantation (P < .001). Corneal coma-like root mean square changed from 0.80 ± 0.53 μm before surgery to 0.61 ± 0.59 μm after surgery (P = .02) for 4.5 mm of pupil size.
  
  
  CONCLUSIONS
  One Ferrara-type ICRS of 150° of arc with a thickness of 150, 200, or 250 μm implanted inferiorly may reduce both astigmatism and corneal coma-like aberrations in keratoconic eyes with no coincident topographic and comatic axes, providing an improvement of UDVA and CDVA values.
authors.affiliation: Fernández-Vega Ophthalmological Institute, Oviedo, Spain. j.alfonso@fernandez-vega.com
authors.forename: José F
authors.initials: JF
authors.lastname: Alfonso
authors.forename: Luis
authors.initials: L
authors.lastname: Fernández-Vega Cueto
authors.forename: Begoña
authors.initials: B
authors.lastname: Baamonde
authors.forename: Jesus
authors.initials: J
authors.lastname: Merayo-Lloves
authors.forename: David
authors.initials: D
authors.lastname: Madrid-Costa
authors.forename: Robert
authors.initials: R
authors.lastname: Montés-Micó
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D003319:Corneal Stroma / Q000503:physiopathology / Q000601:surgery*; D019781:Corneal Topography; D057108:Corneal Wavefront Aberration / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019904:Polymethyl Methacrylate; D011446:Prospective Studies; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D012029:Refraction, Ocular / Q000502:physiology; D012030:Refractive Errors / Q000503:physiopathology; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
chemical_list: D019904:Polymethyl Methacrylate