title: Reliability of pachymetric measurements using orbscan after excimer refractive surgery.
abstract: OBJECTIVE
  To assess the accuracy of pachymetric measurements using Orbscan (Bausch & Lomb, Rochester, NY) after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK).
  
  
  METHODS
  Prospective instrument validation study.
  
  
  METHODS
  Seventy-nine nonoperated normal eyes, 84 eyes after LASIK, and 50 eyes after PRK.
  
  
  METHODS
  Laser in situ keratomileusis or PRK.
  
  
  METHODS
  Central corneal thickness was measured using ultrasound and Orbscan II. The acoustic factor (AF) was adjusted, based on the results obtained in the normal eye group, to minimize the difference between ultrasound and Orbscan pachymetric values.
  
  
  METHODS
  Central corneal thickness as measured by Orbscan and ultrasound pachymeter.
  
  
  RESULTS
  Using the adjusted AF, which was 0.946, the mean difference between Orbscan and ultrasonic pachymetric measurements was 0 +/- 17, 16 +/- 28, and 68 +/- 39 microm in the normal, LASIK, and PRK groups, respectively. The difference between all groups was statistically significant (P < 0.0001).
  
  
  CONCLUSIONS
  Orbscan pachymetric values may be underestimated and less accurate after LASIK and PRK.
authors.affiliation: Fondation Ophtalmologique Adolphe de Rothschild, Hôpital Bichat, 25 à 29 Rue Manin, 75019 Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Prisant
authors.forename: Nila
authors.initials: N
authors.lastname: Calderon
authors.forename: Philippe
authors.initials: P
authors.lastname: Chastang
authors.forename: Damien
authors.initials: D
authors.lastname: Gatinel
authors.forename: Thanh
authors.initials: T
authors.lastname: Hoang-Xuan
mesh_terms: D000328:Adult; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D015203:Reproducibility of Results; D014463:Ultrasonography