title: Repeatability of oculus pentacam metrics derived from corneal topography.
abstract: OBJECTIVE
  To estimate the variability of Scheimpflug imaging measurements over a 1-week period and to determine the impact of age on the measurements and on the variability of the parameters in the study.
  
  
  METHODS
  Three consecutive measurements of anterior and posterior corneal P values (CPVs), central corneal radii (horizontal and vertical), and sagittal corneal radii (at the apex and along an 8-mm diameter ring) were performed on one eye of 23 healthy subjects. Measurements were obtained at 3 different sessions with intervals of a few seconds, 1 hour, and 1 week, under scotopic conditions and immediately after a blink.
  
  
  RESULTS
  In general, no clinically or statistically significant differences were found in within-subjects variance between the three time scales. Confidence limits from Bland and Altman analysis within the first session, and between the first and second sessions, and between the first and third sessions ranged between +/-0.09 and +/-0.18 for anterior and posterior CPV, and between +/-0.03 mm and +/-0.27 mm for anterior and posterior corneal radii (central and sagittal radii). Anterior and posterior corneal measurements and the variability of these measurements were not found to change significantly as a function of age.
  
  
  CONCLUSIONS
  The Oculus Pentacam provides repeatable measures of the metrics derived from corneal topography over the tested time scales. In subjects aged from 19 to 40 years, topography measurements and their respective variability did not seem to change significantly with age.
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom. marco.miranda@postgrad.manchester.ac.uk
authors.forename: Marco A
authors.initials: MA
authors.lastname: Miranda
authors.forename: Hema
authors.initials: H
authors.lastname: Radhakrishnan
authors.forename: Clare
authors.initials: C
authors.lastname: O'donnell
mesh_terms: D000328:Adult; D016001:Confidence Intervals; D019781:Corneal Topography / Q000295:instrumentation* / Q000379:methods*; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D010781:Photography / Q000295:instrumentation*; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D055815:Young Adult