title: A clinical follow up of PRK and LASIK in eyes with preoperative abnormal corneal topographies.
abstract: OBJECTIVE
  To assess the safety and predictability of photorefractive keratotomy (PRK) and laser in situ keratomileusis (LASIK) based on preoperative corneal topography.
  
  
  METHODS
  A non-randomised comparative study was carried out on 84 eyes that presented with topographic abnormalities before undergoing PRK (n = 44) or LASIK (n = 40) procedures. 84 spherical equivalent paired normal eyes served as the control group. Either PRK or LASIK procedures were performed on 168 eyes using the Summit apex plus excimer laser. Topographic abnormalities, including apex displacement (AD), increased asphericity (AS), meridional irregularity (MI), increased inferior-superior asymmetry (IS), increased curvature (CU), and combined features (CO), were assessed preoperatively using the EyeSys analysis system. Safety and predictability of the two procedures were defined as a postoperative visual acuity of 20/40 or better and the loss of one or more lines of spectacle corrected visual acuity (SCVA).
  
  
  RESULTS
  All patients were followed for 6 months. There was a significant loss of best corrected visual acuity in the PRK-AD (p<0.001), PRK-CO (p<0.05), and LASIK-AS (p<0.001) patients. The number of eyes within plus or minus 1.0D of the surgical plan postoperatively was similar in all groups.
  
  
  CONCLUSIONS
  These data suggest that although predictability was similar, PRK and LASIK performed in corneas with topographic abnormalities might cause loss of vision.
authors.affiliation: Ocular Bioengineering Clinic, Federal University of São Paulo, UNIFESP, Brazil. pschor@pabox.com
authors.forename: P
authors.initials: P
authors.lastname: Schor
authors.forename: S M C
authors.initials: SM
authors.lastname: Beer
authors.forename: O
authors.initials: O
authors.lastname: da Silva
authors.forename: R
authors.initials: R
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Campos
mesh_terms: D003316:Corneal Diseases / Q000503:physiopathology / Q000601:surgery*; D019781:Corneal Topography; D005500:Follow-Up Studies; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer; D018903:Photorefractive Keratectomy / Q000379:methods*; D011182:Postoperative Care / Q000379:methods; D011300:Preoperative Care / Q000379:methods; D014792:Visual Acuity / Q000502:physiology