title: Repeatability of aberrometric measurements in normal and keratoconus eyes using a new Scheimpflug-Placido topographer.
abstract: OBJECTIVE
  To evaluate the repeatability of the anterior and posterior corneal wavefront aberrations using the Sirius Scheimpflug-Placido topographer in normal eyes and keratoconus eyes.
  
  
  METHODS
  Bozok University Faculty of Medicine, Yozgat, Turkey.
  
  
  METHODS
  Evaluation of diagnostic test.
  
  
  METHODS
  In eyes of healthy subjects and eyes of keratoconus patients, 3 repeated measurements were obtained using the Scheimpflug-Placido topographer. Repeatability of the corneal aberrometric data using a 7th-order Zernike expansion (6.0 mm pupil) and central corneal power (3.0 mm zone) in the anterior and posterior corneal surfaces were analyzed. The within-subject standard deviation (Sw) and the intraclass correlation coefficient (ICC) were calculated.
  
  
  RESULTS
  For all modal pairs, the Sw was 0.08 μm or less for anterior and posterior corneal aberrations in both groups. The ICC of the anterior corneal surface ranged from 0.607 (pentafoil) to 0.988 (primary coma) in keratoconus eyes (n = 41) and from 0.568 (quadrifoil) to 0.856 (primary coma) in normal eyes (n = 30). The ICCs for posterior corneal surface aberrometry were 0.656 to 0.873 and 0.592 to 0.824, respectively. For anterior and posterior corneal curvatures, the Sw was 0.12 or lower and the ICC values were more than 0.93 in all cases except the posterior corneal surface reading at the 3.0 mm corneal area in keratoconus eyes (ICC 0.875).
  
  
  CONCLUSIONS
  The intraexaminer repeatability of most anterior corneal aberrations with the Scheimpflug-Placido system was moderate to high in normal eyes and keratoconus eyes. The system showed moderate repeatability for the posterior corneal surface.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From Bozok University Medicine Faculty, Ophthalmology Department, Yozgat, Turkey. Electronic address: alihasanbayhan@hotmail.com.
authors.forename: Hasan Ali
authors.initials: HA
authors.lastname: Bayhan
authors.affiliation: From Bozok University Medicine Faculty, Ophthalmology Department, Yozgat, Turkey.
authors.forename: Seray
authors.initials: S
authors.lastname: Aslan Bayhan
authors.affiliation: From Bozok University Medicine Faculty, Ophthalmology Department, Yozgat, Turkey.
authors.forename: Ersin
authors.initials: E
authors.lastname: Muhafız
authors.affiliation: From Bozok University Medicine Faculty, Ophthalmology Department, Yozgat, Turkey.
authors.forename: Izzet
authors.initials: I
authors.lastname: Can
mesh_terms: D057128:Aberrometry / Q000379:methods*; D000328:Adult; D019781:Corneal Topography / Q000295:instrumentation* / Q000379:methods; D057108:Corneal Wavefront Aberration / Q000175:diagnosis*; D064368:Healthy Volunteers; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis*; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D014792:Visual Acuity / Q000502:physiology