title: Measurement of central corneal thickness by high-resolution Scheimpflug imaging, Fourier-domain optical coherence tomography and ultrasound pachymetry.
abstract: OBJECTIVE
  To compare the repeatability and reproducibility of central corneal thickness (CCT) measurements by high-resolution (HR) rotating Scheimpflug imaging and Fourier-domain optical coherence tomography (FD-OCT). CCT measurements were compared to those determined by ultrasound pachymetry (UP).
  
  
  METHODS
  In 35 healthy eyes, intra-observer repeatability for HR Scheimpflug (Pentacam) and FD-OCT (RTVue) systems was determined in consecutive images taken by an observer in the shortest time possible. Imaging was repeated again by a second observer to evaluate inter-observer reproducibility. The CCT measurements were compared among Scheimpflug, FD-OCT and UP images.
  
  
  RESULTS
  Mean coefficients of repeatability were 0.48% for Scheimpflug and 0.26% for FD-OCT. For Scheimpflug, the coefficient of inter-operator reproducibility was 0.87%. For FD-OCT, the coefficient of inter-operator reproducibility was 0.45%. The CCT measurements by Scheimpflug, OCT and UP images were (mean ± standard deviation) 521.7 ± 27.6 μm, 510.8 ± 28.6 μm and 516.5 ± 27.6 μm, respectively. The differences between instruments were statistically significant. The 95% limits of agreement in CCT were -0.7 to 22.5 μm for Pentacam-OCT, -13.4 to 24.0 μm for Pentacam-UP and -26.7 to 15.4 μm for OCT-UP. There was a high degree of correlation between CCT measured by all 3 methods.
  
  
  CONCLUSIONS
  Noncontact measurements of CCT with HR Scheimpflug and FD-OCT systems yielded excellent repeatability and reproducibility and can be used interchangeably. Although both devices were comparable with UP; in clinical practice, the measurements acquired by optical modalities are not directly interchangeable with UP measurements.
authors.affiliation: School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China.
authors.forename: Shihao
authors.initials: S
authors.lastname: Chen
authors.forename: Jinhai
authors.initials: J
authors.lastname: Huang
authors.forename: Daizong
authors.initials: D
authors.lastname: Wen
authors.forename: Wuhe
authors.initials: W
authors.lastname: Chen
authors.forename: David
authors.initials: D
authors.lastname: Huang
authors.forename: Qinmei
authors.initials: Q
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000033:anatomy & histology*; D063171:Corneal Pachymetry / Q000295:instrumentation* / Q000379:methods; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D015588:Observer Variation; D009929:Organ Size; D010781:Photography / Q000295:instrumentation* / Q000379:methods; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000295:instrumentation* / Q000379:methods; D055815:Young Adult