title: Intraocular lens power calculation after laser refractive surgery: corrective algorithm for corneal power estimation.
abstract: OBJECTIVE
  To evaluate an algorithm for corneal power estimation in intraocular lens (IOL) power calculation after myopic laser refractive surgery using direct corneal measurements.
  
  
  METHODS
  International Vision Correction Research Centre, University of Heidelberg, Heidelberg, Germany.
  
  
  METHODS
  Corneal parameters in normal eyes and eyes of refractive surgery cases were evaluated by rotating Scheimpflug imaging. Corneal optical power (K(optical)) calculated by a Gaussian optics formula was simplified as K(optical) = K(anterior) + K(2) (K(anterior) = anterior corneal power; K(posterior) = posterior corneal power; K(2) = K(posterior)--K(anterior) x K(posterior) x corneal thickness/1.376). The variation and change in K(2) induced by refractive surgery were analyzed. A corrective algorithm to calculate K(optical) using mean K(2) (-6.10 diopters [D]), K(corrective) = 1.114 x measured K - 6.10, was derived based on statistical analysis, which was in accordance with the modified Maloney method. The IOL power after refractive surgery was calculated using K(corrective).
  
  
  RESULTS
  The mean K(2) of normal and post-refractive corneas was -6.10 +/- 0.23 D and -6.16 +/- 0.17 D, respectively (P = .17). The mean refractive surgery-induced change in K(2) was -0.06 +/- 0.10 D. The variations in K(2) were small (95% confident interval, -6.55 to -5.65 [normal cornea]; -6.48 to -5.70 [pre-refractive]; - 6.49 to -5.83 [post-refractive)]. Using K(corrective) for IOL power calculation in post-refractive cases yielded mean absolute prediction errors of 0.58 +/- 0.52 D (Haigis), 0.59 +/- 0.49 D (double-K Hoffer Q), and 0.58 +/- 0.47 D (double-K SRK/T).
  
  
  CONCLUSIONS
  The algorithm that induced low error in corneal power estimation was relatively reliable in IOL calculation after myopic laser refractive surgery.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: Guangdong Eye Institute, Guangdong Academy of Medical Sciences, Guangzhou, China.
authors.forename: Haiying
authors.initials: H
authors.lastname: Jin
authors.forename: Mike P
authors.initials: MP
authors.lastname: Holzer
authors.forename: Tanja
authors.initials: T
authors.lastname: Rabsilber
authors.forename: Andreas F
authors.initials: AF
authors.lastname: Borkenstein
authors.forename: Il-Joo
authors.initials: IJ
authors.lastname: Limberger
authors.forename: Haike
authors.initials: H
authors.lastname: Guo
authors.forename: Gerd U
authors.initials: GU
authors.lastname: Auffarth
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003315:Cornea / Q000502:physiology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use*; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery; D055095:Optics and Photonics; D010781:Photography; D011184:Postoperative Period; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results; D014792:Visual Acuity / Q000502:physiology