title: Central corneal thickness measurements with different imaging devices and ultrasound pachymetry.
abstract: OBJECTIVE
  The aim of this study was to compare 4 methods of central corneal thickness (CCT) measurements in terms of their agreement, repeatability, and measurement time.
  
  
  METHODS
  CCT was measured in 184 eyes of 92 healthy subjects by the same examiner. The methods used were as follows: noncontact specular microscopy (SM; Topcon SP-3000P; Topcon Corporation, Tokyo, Japan), Pentacam rotating Scheimpflug photography system (Oculus Inc, Wetzlar, Germany), optical low-coherence reflectometry (OLCR; LenStar LS900; Haag-Streit AG, Koeniz, Switzerland), and ultrasound pachymetry (UP; PachPen; Accutome Inc, Malvern, PA). The duration for each examination was measured by an independent observer.
  
  
  RESULTS
  The mean age (±SD) of the subjects was 54.3 (± 15.3) years. The mean CCTs (± SD) for SM, Pentacam, OLCR, and UP were 507.8 (± 30.2), 538.4 (± 31.7), 531.8 (± 31.4), and 528.3 (± 32.9) μm, respectively. The Bland-Altman plots showed closest agreement for OLCR-UP, followed by OLCR-Pentacam and Pentacam-UP. SM had the poorest agreement with the other methods. CCTs measured by SM were on average 20 to 30 μm thinner than those of the other methods. The coefficient of repeatability for SM, Pentacam, OLCR, and UP were 3.14%, 4.23%, 1.51%, and 3.46%, respectively. The mean measurement times (± SD) were 13.5 (± 5.7), 45.7 (± 12.3), 18.5 (± 7.1), and 5.6 (± 1.0) seconds, respectively.
  
  
  CONCLUSIONS
  CCT measurements between OLCR-UP and OLCR-Pentacam are comparable and can be used interchangeably in clinical practice. However, SM underestimates CCT compared with the other methods, whereas Pentacam was found to be the least repeatable and took the longest time.
authors.affiliation: Department of Ophthalmology, University of Malaya Medical Center, Kuala Lumpur, Malaysia.
authors.forename: Lai-Yong
authors.initials: LY
authors.lastname: Tai
authors.forename: Keat-Ween
authors.initials: KW
authors.lastname: Khaw
authors.forename: Choung-Min
authors.initials: CM
authors.lastname: Ng
authors.forename: Visvaraja
authors.initials: V
authors.lastname: Subrayan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003315:Cornea / Q000033:anatomy & histology*; D063171:Corneal Pachymetry / Q000295:instrumentation*; D003952:Diagnostic Imaging / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult