title: New algorithm for post-radial keratotomy intraocular lens power calculations based on rotating Scheimpflug camera data.
abstract: OBJECTIVE
  To provide an algorithm to calculate intraocular lens (IOL) power for post-radial keratometry (RK) eyes based on data extracted from the Pentacam Scheimpflug camera and to compare calculations with those from an existing standard.
  
  
  METHODS
  Private practice, Mesa, Arizona.
  
  
  METHODS
  Case series.
  
  
  METHODS
  Relevant IOL calculation and postoperative refractive data were obtained for eyes that had previous RK but no additional keratorefractive procedures or subsequent cataract surgery. Various Scheimpflug measurements from examinations before cataract surgery over a range of zone diameters were used to calculate IOL power using an Aramberri double-K-modified Holladay 1 formula. Results were compared with actual postsurgical data and IOL calculations based on the mean of the 1.0 mm to 4.0 mm rings from the Atlas topography system.
  
  
  RESULTS
  Data were obtained for 83 eyes of 57 patients, including more than 120 different measures per eye from the Scheimpflug system. The mean pupil-centered sagittal front power over the central 4.0 mm zone provided the best results after adjustment for central corneal thickness (CCT). Results were similar to those obtained when the IOL power was calculated using the topography system; 42% of eyes were within ± 0.50 diopter (D) of the target, and 76% of eyes were within ± 1.00 D.
  
  
  CONCLUSIONS
  In this large series of eyes, the calculation of IOL power after RK using sagittal front-surface power and CCT from the Scheimpflug system produced results equivalent to the multizone approach with the topography system.
authors: Science in Vision, Burleson, Texas 76028, USA. rpotvinod@earthlink.net
authors: Richard
authors: R
authors: Potvin
authors: Warren
authors: W
authors: Hill
mesh_terms: D000465:Algorithms; D003316:Corneal Diseases / Q000601:surgery*; D019781:Corneal Topography; D006801:Humans; D007646:Keratotomy, Radial; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D055095:Optics and Photonics; D018918:Phacoemulsification; D010781:Photography / Q000295:instrumentation*; D011182:Postoperative Care; D014792:Visual Acuity / Q000502:physiology