title: Fluctuations in corneal curvature limit predictability of intraocular lens power calculations.
abstract: OBJECTIVE
  To analyze fluctuations in corneal curvature over time.
  
  
  METHODS
  Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
  
  
  METHODS
  Case series.
  
  
  METHODS
  A 3-piece IOL was implanted in 1 eye and a 1-piece IOL in the other eye through a 3.2 mm clear corneal temporal incision. Keratometry was performed preoperatively and at several points in time postoperatively. Differences between measurements were analyzed by power vectors. Statistical significance was assessed by monovariate, bivariate, and trivariate paired t tests. Acute angle shifts were determined as differences between meridians at 2 points in time.
  
  
  RESULTS
  Fifty patients were enrolled. From preoperatively to 1 year postoperatively, the changes in vector components (M, J0, J45) were, respectively, -0.02 diopter (D) ± 0.23 (SD) (P=.38), -0.07 ± 0.27 D (P=.02), and +0.04 ± 0.25 D (P=.14). Corresponding changes from 1 year to 2 years postoperatively were +0.01 ± 0.25 D (P=.73), +0.01 ± 0.23 D (P=.83), and +0.01 ± 0.16 D (P=.40). The meridian shift was -5 ± 32 degrees (P=.13) from preoperatively to postoperatively and +3 ± 22 degrees (P=.23) from 1 year to 2 years.
  
  
  CONCLUSIONS
  Surgically induced astigmatism was composed of slight flattening in the horizontal meridian and slight steepening in the oblique meridian but was insignificant in relation to random fluctuations, which were almost equally large between postoperative measurements 1 year apart. The fluctuations were not due to imprecision in measurement.
  
  
  BACKGROUND
  Dr. Norrby is a retiree from Abbott Medical Optics, Inc., and holder of a small amount of stock. Dr. Findl is scientific advisor to Abbott Medical Optics, Inc. No other author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: sverker@home.nl
authors.forename: Sverker
authors.initials: S
authors.lastname: Norrby
authors.forename: Nino
authors.initials: N
authors.lastname: Hirnschall
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Nishi
authors.forename: Oliver
authors.initials: O
authors.lastname: Findl
mesh_terms: D000368:Aged; D001251:Astigmatism / Q000601:surgery; D001699:Biometry / Q000379:methods; D003315:Cornea / Q000033:anatomy & histology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D055095:Optics and Photonics; D018918:Phacoemulsification; D012029:Refraction, Ocular / Q000502:physiology; D013997:Time Factors