title: Agreement and repeatability of central thickness measurement in normal corneas using ultrasound pachymetry and the OCULUS Pentacam.
abstract: OBJECTIVE
  To compare the accuracy and repeatability of the OCULUS Pentacam (a new Scheimpflug-based imaging system) with ultrasound pachymetry in the measurement of central corneal thickness (CCT).
  
  
  METHODS
  CCT was measured in 21 subjects (21 normal corneas) on 2 separate occasions by the same examiner, using an Allergan-Humphrey 850 ultrasonic pachymeter and an OCULUS Pentacam instrument.
  
  
  RESULTS
  Mean values of CCT for both visits for each instrument were 534 +/- 47 microm and 528 +/- 45 microm using the ultrasonic pachymeter and the Pentacam, respectively. Plots of differences against means displayed relatively good agreement (limits of agreement were -13.0 to +26.6 microm). The repeatability (limits of agreement) of the ultrasound pachymeter was -18.3 to +17.7 microm, while for the OCULUS Pentacam it was -24.1 to +21.1 microm.
  
  
  CONCLUSIONS
  Our data showed that the Pentacam instrument provided measurements that were slightly but systematically lower than the measurements provided by ultrasonic pachymetry, which is currently the clinical gold standard method. The results, coupled with a unique ability to image and analyze the anterior chamber in vivo, make the OCULUS Pentacam a promising new instrument for anterior eye evaluation.
authors.affiliation: Faculty of Life Sciences, The University of Manchester, UK. clare.o'donnell@manchester.ac.uk
authors.forename: Clare
authors.initials: C
authors.lastname: O'Donnell
authors.forename: Carole
authors.initials: C
authors.lastname: Maldonado-Codina
mesh_terms: D000328:Adult; D003315:Cornea / Q000000981:diagnostic imaging*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation / Q000706:statistics & numerical data; D004867:Equipment Design; D006801:Humans; D015588:Observer Variation; D012016:Reference Values; D015203:Reproducibility of Results; D014463:Ultrasonography