title: Repeatability of posterior and total corneal curvature measurements with a dual Scheimpflug-Placido tomographer.
abstract: OBJECTIVE
  To evaluate the repeatability of the Galilei G4 dual Scheimpflug analyzer in measuring simulated keratometric, total, and posterior corneal curvature in normal and post-refractive surgery eyes.
  
  
  METHODS
  Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.
  
  
  METHODS
  Prospective evaluation of diagnostic technology.
  
  
  METHODS
  A single observer performed 3 consecutive measurements in 1 eye of each subject. The following were evaluated in both eyes and in eyes that had previous myopic excimer-laser surgery: (1) simulated keratometric corneal power and astigmatism, (2) total corneal power and astigmatism, and (3) posterior corneal power and astigmatism. Repeatability was assessed by calculating the within-subject standard deviation (Sw), coefficient of variation (CoV), and intra-class correlation coefficient (ICC).
  
  
  RESULTS
  The study evaluated 41 normal eyes and 36 post-refractive surgery eyes. In normal eyes, the Sw was 0.08 diopters (D), 0.10 D, and 0.03 D for simulated keratometric, total, and posterior corneal power, respectively. The CoV ranged from 0.16% to 0.40%, and the ICC was 0.992 or more (P < .001) for all corneal powers. In post-refractive surgery eyes, the Sw was 0.09 D, 0.09 D, and 0.02 D for simulated keratometric, total, and posterior corneal power, respectively. The CoV ranged from 0.19% to 0.32%, and the ICC was 0.990 or more (P < .001) for all corneal powers. For posterior corneal astigmatism, the ICC was 0.814 and 0.886 for normal and post-refractive surgery eyes, respectively.
  
  
  CONCLUSIONS
  In normal corneas and corneas that had undergone myopic excimer laser ablation, the dual Scheimpflug analyzer showed high intra-observer repeatability for simulated keratometric, total, and posterior corneal power measurements and moderate repeatability for posterior corneal astigmatism.
  
  
  BACKGROUND
  Drs. Koch, Weikert, and Wang received research support from Ziemer USA, Inc. No other author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Kim
authors.affiliation: From Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Ildamaris
authors.initials: I
authors.lastname: Montes de Oca
authors.affiliation: From Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: From Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Mitchell P
authors.initials: MP
authors.lastname: Weikert
authors.affiliation: From Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Koch
authors.affiliation: From Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA. Electronic address: sumitra.khandelwal@bcm.edu.
authors.forename: Sumitra S
authors.initials: SS
authors.lastname: Khandelwal
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000503:physiopathology; D003315:Cornea / Q000473:pathology*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D010781:Photography / Q000295:instrumentation; D018903:Photorefractive Keratectomy / Q000379:methods*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results; D014054:Tomography / Q000295:instrumentation; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult