title: Reliability of corneal thickness and endothelial cell density measures.
abstract: OBJECTIVE
  We evaluated the reliability and agreement between the Orbscan, an ultrasonic pachymeter (Humphrey 855), and the Konan SP 9000-LC in terms of central corneal thickness. The Konan was also used to study the reliability and agreement between endothelial cell density measures.
  
  
  METHODS
  Twenty-five normal subjects were examined on two occasions (mean separation = 9 +/- 5 days) by a single examiner using all three instruments for central corneal pachymetry. The Konan Center Method and a manual counting method were performed by two examiners to determine endothelial cell density. Reliability and agreement were assessed by calculating the 95% limits of agreement (LoA) and intraclass correlation coefficients (ICC).
  
  
  RESULTS
  For corneal pachymetry test-retest reliability, the 95% limits of agreement were -20 to +17 microm for the ultrasound, -27 to +22 microm for the Konan, and -13 to +13 microm for the Orbscan. There was fair-to-good agreement between the pachymeters (intraclass correlation coefficients range = 0.85 to 0.92). For endothelial cell density test-retest reliability, the 95% limits of agreement for the Konan Center Method was -498 to +530, and -482 to +333 cells/mm2 for examiners 1 and 2, respectively. The test-retest 95% limits of agreement for the manual overlaid grid method was -355 to +355, and -535 to +670 cells/mm2 for examiners 1 and 2, respectively.
  
  
  CONCLUSIONS
  The reliability and agreement of the Orbscan and Konan corneal pachymeters was good, although the reliability of the Konan for estimating endothelial cell density was fair, at best.
authors.affiliation: The Ohio State University, College of Optometry, Columbus, OH 43210, USA. Nichols.142@osu.edu
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Nichols
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Kosunick
authors.forename: Mark A
authors.initials: MA
authors.lastname: Bullimore
mesh_terms: D000328:Adult; D002452:Cell Count; D003315:Cornea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019781:Corneal Topography / Q000295:instrumentation*; D004728:Endothelium, Corneal / Q000166:cytology*; D006801:Humans; D009885:Ophthalmology / Q000295:instrumentation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000295:instrumentation