title: Repeatability of manual subfoveal choroidal thickness measurements in healthy subjects using the technique of enhanced depth imaging optical coherence tomography.
abstract: OBJECTIVE
  The aim of this study was to investigate the repeatability of manual measurements of choroidal thickness in healthy subjects imaged on spectral domain optical coherence tomography (OCT) using the enhanced depth imaging (EDI) technique.
  
  
  METHODS
  Fifty consecutive, healthy, young, adult volunteers with no known eye disease were enrolled prospectively. Two good-quality horizontal and vertical line scans through the fovea were obtained for each eye. Using the manual calipers provided by the software of the proprietary device, two experienced OCT readers measured the subfoveal choroidal thickness (SFCT) of the horizontal and vertical line scans for all eyes. The readers were masked to each other's readings. Intraobserver, interobserver, and intrasession coefficients of repeatability (CRs) were calculated.
  
  
  RESULTS
  Mean (standard deviation [SD]) age of the study subjects was 38 (5) years (range, 30-49 years). Mean (SD) subfoveal choroidal thickness was 332 (90) μm (right eyes) and 332 (91) μm (left eyes). Intraobserver CR was approximately 23 (95% confidence interval [CI], 19-26) μm, whereas interobserver and intrasession CRs were greater at 32 (95% CI, 30-34) and 34 (95% CI, 32-36) μm, respectively. There was no significant difference in SFCT between all pairs of SFCT measurements except for the two intrasession vertical line scans.
  
  
  CONCLUSIONS
  A change of >32 μm was likely to exceed interobserver variability in SFCT. Future studies are required to estimate the repeatability of SFCT measurements in patients with chorioretinal pathology.
authors.affiliation: Moorfields Eye Hospital, London, United Kingdom. waheeda.rahman@moorfields.nhs.uk
authors.forename: Waheeda
authors.initials: W
authors.lastname: Rahman
authors.forename: Fred Kuanfu
authors.initials: FK
authors.lastname: Chen
authors.forename: Jonathan
authors.initials: J
authors.lastname: Yeoh
authors.forename: Praveen
authors.initials: P
authors.lastname: Patel
authors.forename: Adnan
authors.initials: A
authors.lastname: Tufail
authors.forename: Lyndon
authors.initials: L
authors.lastname: Da Cruz
mesh_terms: D000328:Adult; D002829:Choroid / Q000033:anatomy & histology*; D005260:Female; D005584:Fovea Centralis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009929:Organ Size; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*