title: Precision analysis of posterior corneal topography measured by Visante Omni: repeatability, reproducibility, and agreement with Orbscan II.
abstract: OBJECTIVE
  To evaluate the repeatability and reproducibility of posterior corneal curvature and posterior corneal elevation best-fit sphere (BFS) obtained with the Visante Omni (Carl Zeiss Meditec) and to compare the results with the Orbscan II (Bausch & Lomb).
  
  
  METHODS
  Thirty eyes from 30 healthy volunteers were included in this study. All patients were examined 5 times with the Visante Omni and Orbscan II by 2 independent operators. The posterior corneal curvature (3- and 6-mm zone) and posterior corneal elevation BFS (5- and 8-mm zone) were generated for each system. Intraoperator repeatability and interoperator reproducibility and agreement between the systems were evaluated using the intraclass correlation coefficient (ICC) and the Bland-Altman method.
  
  
  RESULTS
  The repeatability of posterior corneal curvature and posterior corneal elevation BFS measured by the Visante Omni was high for all analysis zones (ICC, 0.99 to 1.00). The reproducibility also showed similar results (ICC, 0.99 to 1.00). Agreement between the Visante Omni and Orbscan II was high for posterior corneal curvature (ICC, 0.94 to 0.97) and posterior corneal elevation BFS (ICC, 0.96 to 0.98) with 95% limits of agreement at -0.26 to 0.22 diopters for posterior corneal curvature and 0.11 to 0.69 mm for posterior corneal elevation BFS.
  
  
  CONCLUSIONS
  The Visante Omni provides good repeatability and reproducibility of posterior corneal topography. Overall agreement with the Orbscan II system was high.
authors.affiliation: Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Sabong
authors.initials: S
authors.lastname: Srivannaboon
authors.forename: Suksri
authors.initials: S
authors.lastname: Chotikavanich
authors.forename: Chareenun
authors.initials: C
authors.lastname: Chirapapaisan
authors.forename: Sirilux
authors.initials: S
authors.lastname: Kasemson
authors.forename: Wasin
authors.initials: W
authors.lastname: Po-ngam
mesh_terms: D000328:Adult; D019781:Corneal Topography / Q000592:standards*; D004728:Endothelium, Corneal / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D015588:Observer Variation; D015203:Reproducibility of Results; D055815:Young Adult