title: Dual versus single Scheimpflug camera for anterior segment analysis: Precision and agreement.
abstract: OBJECTIVE
  To assess the repeatability, reproducibility, and agreement of the Pentacam HR single-camera and Galilei G2 dual-camera Scheimpflug devices in anterior segment analysis.
  
  
  METHODS
  Begitek Clínica Oftalmológica, San Sebastián, Spain.
  
  
  METHODS
  Prospective randomized observational study.
  
  
  METHODS
  Healthy young individuals had 3 consecutive tests by 2 examiners. Analyzed parameters were anterior and posterior cornea simulated keratometry (K), K flat, K steep, astigmatism magnitude and axis, J(0) and J(45) vectors, asphericity, total corneal higher-order wavefront aberrations (root mean square [RMS], coma, trefoil, spherical aberration), central cornea and thinnest-point thicknesses, and anterior chamber depth. Repeatability and reproducibility were evaluated by calculating the within-subject standard deviation (S(w)), some derived coefficients, and the intraclass correlation coefficient. Agreement was assessed with the Bland-Altman method.
  
  
  RESULTS
  The single-camera device reproducibility (S(w)) was simulated K, 0.04 diopter (D); J(0), 0.03 D; J(45), 0.04 D; total power, 0.04 D; spherical aberration, 0.02 μm; higher-order aberrations (HOAs), 0.02 μm; central corneal thickness (CCT), 3.39 μm. The dual-camera device S(w) was simulated K, 0.07 D; J(0), 0.13 D; J(45), 0.04 D; total power, 0.08 D; spherical aberration, 0.02 μm; HOAs, 0.11 μm; CCT, 1.36 μm. Agreement was good for most parameters except total corneal power (mean difference 1.58 D ± 0.22 (SD) and HOA RMS (mean difference 0.48 ± 0.19 μm) (both P<.00).
  
  
  CONCLUSIONS
  Repeatability and reproducibility were good for all parameters. The single-camera device was more precise for curvature, astigmatism, and corneal wavefront error measurements and the dual-camera device for pachymetry measurements. Agreement was good with some relevant exceptions.
  
  
  BACKGROUND
  Dr. Aramberri is consultant to Costruzione Strumenti Oftalmici, Firenze, Italy. No other author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: Begitek Clínica Oftalmológica, San Sebastián, Spain. jaimearamberri@telefonica.net
authors.forename: Jaime
authors.initials: J
authors.lastname: Aramberri
authors.forename: Luis
authors.initials: L
authors.lastname: Araiz
authors.forename: Ane
authors.initials: A
authors.lastname: Garcia
authors.forename: Igor
authors.initials: I
authors.lastname: Illarramendi
authors.forename: Jaione
authors.initials: J
authors.lastname: Olmos
authors.forename: Izaskun
authors.initials: I
authors.lastname: Oyanarte
authors.forename: Amaya
authors.initials: A
authors.lastname: Romay
authors.forename: Itxaso
authors.initials: I
authors.lastname: Vigara
mesh_terms: D000328:Adult; D000867:Anterior Chamber / Q000033:anatomy & histology; D000869:Anterior Eye Segment / Q000033:anatomy & histology*; D057108:Corneal Wavefront Aberration / Q000175:diagnosis; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D010781:Photography / Q000295:instrumentation* / Q000592:standards; D011446:Prospective Studies; D012016:Reference Values; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results