title: Repeatability, reproducibility, and agreement of corneal power measurements obtained with a new corneal topographer.
abstract: OBJECTIVE
  To study the repeatability and reproducibility of corneal power measurements obtained with a new corneal topographer (Keratograph 4) and assess their agreement with those obtained by a rotating Scheimpflug camera (Pentacam HR) and an automated keratometer (IOLMaster).
  
  
  METHODS
  Eye Hospital, Wenzhou Medical University, Wenzhou, China.
  
  
  METHODS
  Observational cross-sectional study.
  
  
  METHODS
  One eye of normal subjects was measured 3 times using all devices. Another operator performed an additional 3 consecutive scans using the corneal topographer. One week later, the first operator repeated the corneal power measurements using the corneal topographer. Parameters were flat meridian power, steep meridian power, average power, J0, and J45. The repeatability and reproducibility of measurements were assessed by the within-subject standard deviation (Sw), repeatability (2.77 Sw), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). Agreement between devices was assessed using 95% limits of agreement (LoA).
  
  
  RESULTS
  Intraoperator repeatability and interoperator and intersession reproducibility of all measured parameters showed a CoV of less than 0.3%, a 2.77 Sw of 0.32 diopter or less, and an ICC of more than 0.97. No significant differences in the parameters were noted between the corneal topographer and Scheimpflug camera. Statistically significant differences existed between the parameters analyzed by the corneal topographer and the automated keratometer, except J45. The mean differences between the corneal topographer and the other 2 devices were small, and the 95% LoA were narrow for all measurements.
  
  
  CONCLUSIONS
  The new corneal topographer had excellent reliability and high agreement with the other 2 devices in corneal power measurements in normal subjects.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the School of Optometry and Ophthalmology and Eye Hospital (Mao, Zhuo, Feng, Wang, Chen, Huang), Wenzhou Medical University, the Key Laboratory of Vision Science (Mao, Zhuo, Wang, Chen, Huang), Ministry of Health P.R. China, and the Department of Ophthalmology (Zhang), First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China; the G.B. Bietti Foundation IRCCS (Savini), Rome, Italy.
authors.forename: Xinjie
authors.initials: X
authors.lastname: Mao
authors.forename: Giacomo
authors.initials: G
authors.lastname: Savini
authors.forename: Zuopao
authors.initials: Z
authors.lastname: Zhuo
authors.forename: Yifan
authors.initials: Y
authors.lastname: Feng
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Qinmei
authors.initials: Q
authors.lastname: Wang
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.forename: Jinhai
authors.initials: J
authors.lastname: Huang
mesh_terms: D000328:Adult; D003315:Cornea / Q000033:anatomy & histology / Q000502:physiology*; D019781:Corneal Topography / Q000295:instrumentation*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D012016:Reference Values; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results; D055815:Young Adult