title: Accuracy of Orbscan II in the assessment of posterior curvature in patients with myopic LASIK.
abstract: OBJECTIVE
  To evaluate the accuracy of Orbscan II measurements in assessing posterior corneal curvature in patients undergoing myopic LASIK.
  
  
  METHODS
  Using the Orbscan II, posterior corneal curvature was assessed pre- and postoperatively in 304 eyes that underwent myopic LASIK. The radius of curvature and corneal refractive power in diopters (D) were compared using the paired sample t test.
  
  
  RESULTS
  The mean pre- and postoperative radius of posterior corneal curvature were 6.49 +/- 0.26 mm and 6.35 +/- 0.30 mm, respectively. Mean pre- and postoperative posterior corneal power were -6.17 +/- 0.25 D and -6.32 +/- 0.30 D, respectively, and the difference (0.14 +/- 0.14 D) was statistically significant (P < .01).
  
  
  CONCLUSIONS
  Although the derived value for the power of the postoperative LASIK posterior corneal surface is overestimated using the Orbscan II, this small difference may not be clinically important. Orbscan II measurements can therefore be used (with caution) to measure posterior corneal curvature in patients with myopic LASIK for the assessment of intraocular lens power based on the Gaussian optics formula.
authors.affiliation: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Kowloon, Hong Kong. artcheng@netvigator.com
authors.forename: Arthur C K
authors.initials: AC
authors.lastname: Cheng
authors.forename: Srinivas K
authors.initials: SK
authors.lastname: Rao
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery; D019781:Corneal Topography; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D007910:Lenses, Intraocular; D009216:Myopia / Q000601:surgery*; D011184:Postoperative Period; D011300:Preoperative Care; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results; D012189:Retrospective Studies