title: Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects.
abstract: OBJECTIVE
  To determine (1) repeatability of central corneal thickness (CCT) measurements by spectral domain optical coherence tomography (RTVue; Optovue, Inc, Fremont, CA) and (2) agreement between CCT measurements by RTVue and those by ultrasonic pachymetry, Orbscan, and anterior segment optical coherence tomography (ASOCT).
  
  
  METHODS
  In a prospective observational study, 2 cohorts of normal subjects were recruited. In the first cohort (51 subjects), 5 measurements of CCT were obtained by RTVue during the same visit to determine the repeatability. In the second cohort (65 subjects), CCT measurements were obtained by RTVue, ultrasonic pachymetry, Orbscan, and ASOCT during the same visit to determine the agreement among these instruments. Repeatability was assessed by intraclass correlation coefficient (ICC), within-subject standard deviation, coefficient of repeatability, and within-subject coefficient of variation. Agreement was assessed by ICC and Bland and Altman plots.
  
  
  RESULTS
  Repeatability of CCT measurements by RTVue as assessed by ICC, within-subject standard deviation, coefficient of repeatability, and within-subject coefficient of variation was 0.99 (0.99-0.99), 2.2 (1.9-2.5), 4.2 μm (3.6-4.8), and 0.4% (0.3-0.5), respectively. The average CCT by RTVue (529 μm) was comparable to that by ultrasonic pachymetry (539 μm; P = 0.15), Orbscan (536 μm; P = 0.54), and ASOCT (526 μm; P = 0.77). The 95% limits of agreement on Bland and Altman plots ranged from 20 μm (between RTVue and ASOCT) to 33 μm (between RTVue and Orbscan).
  
  
  CONCLUSIONS
  CCT measurements by RTVue have an excellent repeatability. Although CCT measurements by RTVue are comparable to that by ultrasonic pachymetry, Orbscan, and ASOCT, the difference between instruments can be significant depending on the clinical situation considered.
authors.affiliation: L V Prasad Eye Institute, Banjara Hills, Hyderabad, India. harsha@lvpei.org
authors.forename: Harsha Laxmana
authors.initials: HL
authors.lastname: Rao
authors.forename: Addepalli Uday
authors.initials: AU
authors.lastname: Kumar
authors.forename: Anjul
authors.initials: A
authors.lastname: Kumar
authors.forename: Swathi
authors.initials: S
authors.lastname: Chary
authors.forename: Sirisha
authors.initials: S
authors.lastname: Senthil
authors.forename: Pravin Krishna
authors.initials: PK
authors.lastname: Vaddavalli
authors.forename: Chandra Sekhar
authors.initials: CS
authors.lastname: Garudadri
mesh_terms: D000328:Adult; D000368:Aged; D000869:Anterior Eye Segment / Q000033:anatomy & histology; D015331:Cohort Studies; D003315:Cornea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019781:Corneal Topography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D014463:Ultrasonography