title: Posterior corneal elevation after LASIK with three flap techniques as measured by Pentacam.
abstract: OBJECTIVE
  To evaluate and compare posterior corneal changes using elevation data obtained from Pentacam (Oculus Optikgeräte GmbH) Scheimpflug imaging in eyes undergoing LASIK with three different modes of flap creation: IntraLase femtosecond laser FS60 (Abbott Medical Optics) (femtosecond group), Amadeus (Ziemer Group AG) mechanical microkeratome (keratome group), or flap formation using 20% alcohol laser epithelial keratomileusis (LASEK) (LASEK group).
  
  
  METHODS
  Ninety myopic patients (90 eyes) undergoing refractive surgery were recruited. The change in posterior corneal elevation at 21 predetermined points in the central 5-mm area was measured using exported elevation data from the Pentacam before LASIK and 18 months postoperative and was compared among and within three modes of flap creation.
  
  
  RESULTS
  Mean change in posterior elevation in the central 5-mm area was 5.13±4.16 μm for the femtosecond group, 5.78±4.42 μm for the keratome group, and 6.68±4.72 μm for the LASEK group and was similar among groups (P=.59). Change in posterior elevation before and after LASIK was not significant within any group (P=.342, P=.232, and P=.321 for the femtosecond, keratome, and LASEK groups, respectively). Preoperative spherical equivalent, central corneal thickness, ablation depth, and estimated residual bed thickness did not correlate with change in posterior corneal elevation for the femtosecond, keratome, or LASEK groups (P>.05).
  
  
  CONCLUSIONS
  Using Pentacam elevation data, there were no significant changes in posterior corneal elevation following LASIK among or within the three methods of flap creation. At 18 months after LASIK, the posterior corneal surface is not displaced anteriorly significantly and is equally stable using these three surgical techniques.
authors.affiliation: Grewal Eye Institute, Chandigarh, India. dilraj@gmail.com
authors.forename: Dilraj S
authors.initials: DS
authors.lastname: Grewal
authors.forename: Gagandeep S
authors.initials: GS
authors.lastname: Brar
authors.forename: Satinder Pal Singh
authors.initials: SP
authors.lastname: Grewal
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000473:pathology; D003319:Corneal Stroma / Q000601:surgery*; D004108:Dilatation, Pathologic / Q000175:diagnosis; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D009216:Myopia / Q000601:surgery*; D010781:Photography / Q000379:methods*; D011446:Prospective Studies; D013524:Surgical Flaps; D055815:Young Adult