title: Optical quality after myopic photorefractive keratectomy and laser in situ keratomileusis: comparison using a double-pass system.
abstract: OBJECTIVE
  To use a double-pass system to compare the optical quality after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for mild to moderate myopia.
  
  
  METHODS
  Universitat Politècnica de Catalunya, Terrassa, Barcelona Institute of Ocular Microsurgery, Barcelona, Spain.
  
  
  METHODS
  Comparative case series.
  
  
  METHODS
  Optical quality was assessed with a clinical double-pass system preoperatively and 3 months after PRK or LASIK. The modulation transfer function (MTF), retinal image quality parameters (MTF cutoff frequency, Strehl ratio), and intraocular scattering (objective scatter index [OSI]) were calculated.
  
  
  RESULTS
  This study evaluated 34 eyes that had PRK and 55 eyes that had LASIK. Both PRK and LASIK had a statistically significant impact on retinal image quality, although no significant differences between the techniques were observed. The MTF at 30 cycles per degree decreased by a factor of 1.50 in the PRK group and by a factor of 1.32 in the LASIK group. The MTF cutoff frequency decreased by a factor of 1.04 in the PRK group and by a factor of 1.06 in the LASIK group. The Strehl ratio decreased by a factor of 1.10 and 1.07, respectively. Photorefractive keratectomy and LASIK increased the objective scatter index by factors of 1.48 and 1.57, respectively. Significant correlations between the preoperative refraction and the OSI were found.
  
  
  CONCLUSIONS
  Retinal image quality was similarly reduced with PRK and LASIK, with no significant differences between the 2 methods. Some PRK patients had a residual refractive error that might have been related to corneal-wound healing still present 3 months postoperatively.
authors.affiliation: Universitat Politècnica de Catalunya, Terrassa, Barcelona, Spain.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Ondategui
authors.forename: Meritxell
authors.initials: M
authors.lastname: Vilaseca
authors.forename: Montserrat
authors.initials: M
authors.lastname: Arjona
authors.forename: Ana
authors.initials: A
authors.lastname: Montasell
authors.forename: Genís
authors.initials: G
authors.lastname: Cardona
authors.forename: José L
authors.initials: JL
authors.lastname: Güell
authors.forename: Jaume
authors.initials: J
authors.lastname: Pujol
mesh_terms: D000328:Adult; D003319:Corneal Stroma; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008027:Light; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D012160:Retina / Q000502:physiology*; D012542:Scattering, Radiation; D013524:Surgical Flaps; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult