title: Keratometry for intraocular lens power calculation using Orbscan II in eyes with laser in situ keratomileusis.
abstract: OBJECTIVE
  To compare the results of comeal keratometry after laser in situ keratomileusis (LASIK) obtained by the Gaussian optics formula and the clinical history method.
  
  
  METHODS
  Sixty-one consecutive patients (121 eyes) who had undergone LASIK were recruited in this retrospective case-controlled study. The K-value obtained from the Gaussian optics formula (CalK) based on postoperative corneal topography by Orbscan II (Bausch & Lomb, Rochester, NY) and ultrasound pachymetry was compared with that obtained from the clinical history method (estK). Keratometry measured by these two methods was compared using the paired sample t test and Pearson correlation coefficient.
  
  
  RESULTS
  A high correlation was noted between K-value obtained by the clinical history method and the Gaussian optics formula (R = 0.97, P < .001). The mean difference between the two methods is 0.13 diopters (P = .06).
  
  
  CONCLUSIONS
  K reading derived from the Gaussian optics formula correlated closely to that obtained from the clinical history method and would be especially useful in patients with no preoperative LASIK treatment data.
authors.affiliation: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, University Eye Center, Hong Kong Eye Hospital, Kowloon, Hong Kong. arthurcheng@cuhk.edu.hk
authors.forename: Arthur C K
authors.initials: AC
authors.lastname: Cheng
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D001699:Biometry / Q000379:methods; D016022:Case-Control Studies; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D055095:Optics and Photonics; D012030:Refractive Errors / Q000503:physiopathology; D054140:Refractive Surgical Procedures; D012189:Retrospective Studies