title: A comprehensive evaluation of the precision (repeatability and reproducibility) of the Oculus Pentacam HR.
abstract: OBJECTIVE
  To evaluate the precision (repeatability and reproducibility) of the Pentacam HR (high-resolution) tomographer (Oculus, Wetzlar, Germany) across a large range of measurement parameters.
  
  
  METHODS
  A randomly selected healthy eye of 100 subjects was scanned twice with the Pentacam HR by one observer for each of the three measurement modes: 25-picture (1 second) scan, 50-picture (2 second) scan, and cornea fine scan (50 pictures in 1 second). The repeatability of each scan mode was assessed. One additional 25-picture scan was acquired by a second observer to test reproducibility.
  
  
  RESULTS
  Overall, the Pentacam HR had good precision, with the cornea fine scan returning the most precise results: The 25- and 50-picture scans showed similar precision. The repeatability limits, expressed as the within-subject SD × 1.96√2 of the anterior keratometry (K)1 and K2 readings with the standard 25-picture scan, were 0.25 and 0.36 D, respectively. Pachymetry maps, corneal maps, anterior chamber depth maps, corneal volume, topometric Q values and indices were also found to be precise. Poor precision was found for estimates of axis (astigmatic and progression index), pupil center pachymetry, single points on corneal maps, refractive power maps, and equivalent K readings.
  
  
  CONCLUSIONS
  Measurements taken with the Pentacam HR are repeatable and reproducible, especially those obtained with the cornea fine scan. Although the Pentacam HR is clearly a very useful clinical and research tool, the measurement of corneal axes, pupil center pachymetry, front meridional and axial maps, refractive power maps, and equivalent K readings should be interpreted with caution.
authors.affiliation: Department of Optometry and Vision Science, Flinders Medical Centre and Flinders University of South Australia, Bedford Park, South Australia 5042, Australia. colm.mcalinden@gmail.com
authors.forename: Colm
authors.initials: C
authors.lastname: McAlinden
authors.forename: Jyoti
authors.initials: J
authors.lastname: Khadka
authors.forename: Konrad
authors.initials: K
authors.lastname: Pesudovs
mesh_terms: D000328:Adult; D000368:Aged; D000867:Anterior Chamber / Q000033:anatomy & histology*; D003315:Cornea / Q000033:anatomy & histology*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000033:anatomy & histology; D008297:Male; D008875:Middle Aged; D010781:Photography / Q000295:instrumentation*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results; D014054:Tomography / Q000295:instrumentation*; D055815:Young Adult