title: Femtosecond laser-assisted intrastromal corneal ring segment implantation for high astigmatism correction after penetrating keratoplasty.
abstract: OBJECTIVE
  To assess the visual and refractive outcomes of femtosecond laser-assisted implantation of Ferrara-type intrastromal corneal ring segments (ICRS) in post-penetrating keratoplasty (PKP) eyes.
  
  
  METHODS
  Instituto Oftalmológico Fernández-Vega, Oviedo, Spain.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  Patients with previous PKP had ICRS implantation after femtosecond laser tunnel creation. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities and residual refractive errors were recorded before and 6 months after ICRS implantation. The power vector method was used to analyze refractive errors preoperatively and postoperatively.
  
  
  RESULTS
  This study enrolled 32 eyes of 30 patients. The mean UDVA (Snellen decimal) changed from 0.16 ± 0.15 (SD) preoperatively to 0.43 ± 0.28 postoperatively (P<.0001). Postoperatively, the UDVA was 20/40 or better in 40.6% of eyes. The mean CDVA was 0.67 ± 0.22 preoperatively and 0.80 ± 0.19 postoperatively (P<.0001). Postoperatively, the CDVA was better than 20/40 in 96.9% of eyes and 20/25 or better in 56.2% of eyes. By 6 months postoperatively, no eye had lost more than 2 lines of CDVA, 4 eyes lost 1 line, 6 eyes had no change, 9 eyes gained 1 line, and 13 eyes gained 2 or more lines. The safety index at 6 months was 1.20. The spherical equivalent and astigmatism components were significantly reduced after ICRS implantation (P<.04).
  
  
  CONCLUSIONS
  Intrastromal corneal ring segment implantation using the femtosecond laser may be a good alternative for high astigmatism correction in post-PKP eyes.
authors.affiliation: From the Instituto Oftalmológico Fernández-Vega (Lisa, García-Fernández, Merayo-Lloves, Alfonso), the Surgery Department (Merayo-Lloves, Alfonso), School of Medicine, University of Oviedo, Oviedo, and the Optics Department (Madrid-Costa), Faculty of Physics, University of Valencia, Spain; the Brazilian Study Group of Artificial Intelligence and Cornea (Torquetti), Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Lisa
authors.forename: Miriam
authors.initials: M
authors.lastname: García-Fernández
authors.forename: David
authors.initials: D
authors.lastname: Madrid-Costa
authors.forename: Leonardo
authors.initials: L
authors.lastname: Torquetti
authors.forename: Jesús
authors.initials: J
authors.lastname: Merayo-Lloves
authors.forename: José Fernando
authors.initials: JF
authors.lastname: Alfonso
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D015331:Cohort Studies; D003316:Corneal Diseases / Q000601:surgery; D003319:Corneal Stroma / Q000601:surgery*; D005260:Female; D006801:Humans; D015948:Keratoplasty, Penetrating / Q000009:adverse effects*; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019904:Polymethyl Methacrylate; D011446:Prospective Studies; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D012029:Refraction, Ocular / Q000502:physiology; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
chemical_list: D019904:Polymethyl Methacrylate