title: Central corneal thickness measurements with partial coherence interferometry, ultrasound, and the Orbscan system.
abstract: OBJECTIVE
  To compare the reliability of central corneal thickness measurements (CCT) obtained with partial coherence interferometry (PCI), ultrasound pachymetry, and the Orbscan system.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Twenty healthy subjects with CCT measurements in both eyes.
  
  
  METHODS
  The CCT measurements were obtained with PCI, ultrasound pachymetry, and the Orbscan system. In each eye, 2 investigators performed 5 repeated measurements with each pachymetric device. Intraclass correlation coefficients (kappa) were calculated and mean CCT measurements were compared.
  
  
  METHODS
  The CCT measurements obtained with ultrasound pachymetry, the Orbscan system (Orbtek Inc., Salt Lake City, UT), and PCI.
  
  
  RESULTS
  Mean CCT values measured with ultrasound pachymetry were significantly thicker than those measured with PCI (21.5 microm; P<0.001) or the Orbscan system (19.8 microm; P<0.001). The correlation coefficients for the intraobserver variability were 0.999 for PCI measurements, 0.983 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. The correlation coefficients for the interobserver variability were 0.998 for PCI measurements, 0.980 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. There was a slightly better consistency between ultrasound pachymetry and PCI (kappa = 0.96) than between the Orbscan system and PCI (kappa = 0.92) and between ultrasound pachymetry and the Orbscan system (kappa = 0.89).
  
  
  CONCLUSIONS
  Partial coherence interferometry was the method with the least intraobserver or interobserver variability. Mean CCT as measured with ultrasound pachymetry was approximately 20 microm thicker than with the Orbscan system and PCI. However, corneal thickness measurements with ultrasound pachymetry and PCI were slightly more consistent than those of the Orbscan system and PCI. This slightly better consistency, however, may be important, especially in corneal refractive surgery.
authors.affiliation: Department of Ophthalmology, University of Vienna, Vienna, Austria. georg.rainer@akh-wien.ac.at
authors.forename: Georg
authors.initials: G
authors.lastname: Rainer
authors.forename: Oliver
authors.initials: O
authors.lastname: Findl
authors.forename: Vanessa
authors.initials: V
authors.lastname: Petternel
authors.forename: Barbara
authors.initials: B
authors.lastname: Kiss
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Drexler
authors.forename: Christian
authors.initials: C
authors.lastname: Skorpik
authors.forename: Michael
authors.initials: M
authors.lastname: Georgopoulos
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D019412:Anatomy, Cross-Sectional; D001837:Body Weights and Measures; D003315:Cornea / Q000033:anatomy & histology*; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007368:Interferometry / Q000379:methods; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D014463:Ultrasonography