title: Topography-based screening for previous laser in situ keratomileusis to correct myopia and hyperopia.
abstract: OBJECTIVE
  To develop a screening tool based on corneal topography to detect previous myopic and hyperopic laser in situ keratomileusis (LASIK).
  
  
  METHODS
  Clinical data from three private clinics were analyzed in a university setting. A total of 476 topographies (Orbscan II) were randomly selected (1 topography per patient): 338 from unoperated corneas, 81 from corneas that had LASIK to correct myopia, and 57 from corneas that had LASIK to correct hyperopia. The LASIK procedures were performed using a Technolas excimer laser (217C or 217Z) and a Hansatome microkeratome. The first set of algorithms (VESm and VESh) calculated the volume summation between the anterior corneal surface and the best-fit sphere in the central and mid-peripheral regions. The second set of algorithms (DCm and DCh) calculated the mean anterior tangential curvature difference between the central and mid-peripheral regions.
  
  
  RESULTS
  The features VESm and DCm for the screening of a myopic LASIK yield, respectively, sensitivity rates of 92.7% and 95.1% and specificity rates of 94.9% and 96.5%. The features VESh and DCh for the screening of a hyperopic LASIK gave sensitivity rates of 93.1% for both and specificity rates of 94.8% and 97.1%. The performance of those features was superior to clinical assessment using topography color maps.
  
  
  CONCLUSIONS
  Criteria based on Orbscan II corneal topography are proposed for the detection of previous hyperopic and myopic LASIK performed with a Technolas excimer laser (version 217C or 217Z).
authors.affiliation: Department of Computer Science and Operations Research, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Laliberté
authors.forename: Jean
authors.initials: J
authors.lastname: Meunier
authors.forename: Sandrine
authors.initials: S
authors.lastname: Hick
authors.forename: Isabelle
authors.initials: I
authors.lastname: Brunette
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D001251:Astigmatism / Q000175:diagnosis / Q000601:surgery; D003315:Cornea / Q000473:pathology* / Q000601:surgery; D019781:Corneal Topography / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000175:diagnosis* / Q000601:surgery; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000175:diagnosis* / Q000601:surgery; D012680:Sensitivity and Specificity