title: Reproducibility and Daytime-Dependent Changes of Corneal Epithelial Thickness and Whole Corneal Thickness Measured With Fourier Domain Optical Coherence Tomography.
abstract: OBJECTIVE
  To evaluate the reproducibility of Fourier domain anterior segment optical coherence tomography (RTVue) based on repeated measurements of corneal thickness (CT) and epithelial thickness (ET) and to test daytime-dependent changes of these parameters.
  
  
  METHODS
  Twenty-three eyes from 23 healthy volunteers were included in this prospective study. Three clinical observers performed 3 consecutive measurements each of CT and ET in 3 sessions using RTVue, resulting in 9 measurements per session. Session 1 was performed at 9 AM ± 1 hour, session 2 at 4 PM ± 1 hour on the same day, and session 3 at 9 AM ± 1 hour 2 days later. CT and ET were assessed in 9 areas: corneal vertex, 4 paracentral zones, and 4 peripheral zones.
  
  
  RESULTS
  The mean intraclass correlations (ICCs) for intraobserver and interobserver reproducibility were almost perfect (0.81-0.99) for CT in all corneal zones and for ET in all but 2 peripheral zones. Intraobserver ICC was substantial (0.61-0.8) for superior peripheral area and interobserver ICC for superior and inferior peripheral positions. CT and ET decreased significantly from morning to afternoon sessions [-3.15 μm (P < 0.0001) and -0.52 μm (P < 0.0001), respectively]. ET correlated weakly to moderately with CT.
  
  
  CONCLUSIONS
  RTVue yields almost perfect reproducibility for CT and ET in central, paracentral, and peripheral lateral zones. Central CT and ET were significantly thinner in the afternoon compared with the morning.
authors.affiliation: *Department of Ophthalmology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany; and †Institute for Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany.
authors.forename: Joanna
authors.initials: J
authors.lastname: Wasielica-Poslednik
authors.forename: Walter
authors.initials: W
authors.lastname: Lisch
authors.forename: Katharina
authors.initials: K
authors.lastname: Bell
authors.forename: Veronika
authors.initials: V
authors.lastname: Weyer
authors.forename: Norbert
authors.initials: N
authors.lastname: Pfeiffer
authors.forename: Adrian
authors.initials: A
authors.lastname: Gericke
mesh_terms: D000328:Adult; D003315:Cornea / Q000033:anatomy & histology*; D019573:Epithelium, Corneal / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*