title: Refractive error after triple and non-simultaneous procedures: is the application of a standard constant keratometry value in IOL power calculation advisable?
abstract: OBJECTIVE
  The purpose of this investigation was to determine whether or not the use of a standard constant keratometry value in cases of preoperative abnormal keratometry values in biometry for triple procedures is advisable.
  
  
  METHODS
  Cataract surgery and penetrating keratoplasty were performed in 82 eyes; 53 eyes underwent triple procedures and 29 eyes underwent non-simultaneous procedures. A standard constant keratometry value of 42.50 D was applied in 18 triple-procedure eyes because the preoperative measured keratometry values were outwith the normal range (41-47 D). The spherical equivalent and expected values were compared after a mean follow-up of 20.5 months.
  
  
  RESULTS
  Cases in the triple-procedure group that achieved spherical equivalent within +/- 2.0 D of expected values included nine of 18 eyes (50%) in which a standard constant keratometry value of 42.50 D was applied, three of 17 eyes (18%) in which keratometry values outwith the normal range were applied (p = 0.044), and eight of 18 eyes (45%) in which keratometry values within the normal range were applied (p = 0.862). Cases in the non-simultaneous procedure group that achieved spherical equivalent within +/- 2.0 D of expected values included 22 of 24 eyes (92%) in which keratometry values within the normal range were applied (p = 0.0025), and five of five eyes (100%) in which a standard constant keratometry value was applied.
  
  
  CONCLUSIONS
  The application of a standard constant keratometry value of 42.50 D for intraocular lens power calculation in triple procedures can be recommended if abnormal keratometry values were measured previously. If possible, non-simultaneous procedures should take priority.
authors.affiliation: Department of Ophthalmology, Martin-Luther-University, Halle, Germany. claudia.gruenauer-kloevekorn@medizin.uni-halle.de
authors.forename: Claudia
authors.initials: C
authors.lastname: Gruenauer-Kloevekorn
authors.forename: Kristian
authors.initials: K
authors.lastname: Kloevekorn-Norgall
authors.forename: Gernot I W
authors.initials: GI
authors.lastname: Duncker
authors.forename: Anke
authors.initials: A
authors.lastname: Habermann
mesh_terms: D001699:Biometry; D003315:Cornea / Q000503:physiopathology; D006801:Humans; D015948:Keratoplasty, Penetrating / Q000009:adverse effects*; D019654:Lens Implantation, Intraocular / Q000009:adverse effects*; D007910:Lenses, Intraocular; D049451:Nomograms; D055095:Optics and Photonics; D018918:Phacoemulsification / Q000009:adverse effects*; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000209:etiology* / Q000503:physiopathology; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology