title: Comparative analysis of repeatability of manual and automated choroidal thickness measurements in nonneovascular age-related macular degeneration.
abstract: OBJECTIVE
  We compared the reproducibility and mutual agreement of the subfoveal choroidal thickness measurements by expert raters and an automated algorithm in enhanced depth imaging optical coherence tomography (EDI-OCT) images of eyes with nonneovascular age-related macular degeneration (AMD).
  
  
  METHODS
  We recruited 44 patients with nonneovascular AMD and EDI-OCT images were acquired. Subfoveal choroidal thickness was measured manually by two expert raters and automatically by a graph-cut-based algorithm. Drusen area was measured using the automated software (version 6) of Cirrus SD-OCT. The manual and automated choroidal thickness measurements were compared in reproducibility, mutual agreement, and correlation with drusen area.
  
  
  RESULTS
  The mean subfoveal choroidal thickness was 246 ± 63 μm for the first rater, 214 ± 68 for the second rater, and 209 ± 53 for the automated algorithm. Intraclass correlation coefficients (ICC) and 95% confidence intervals (CI) were 0.96 (CI 0.94-0.98) between the raters, 0.85 (CI 0.77-0.90) between the first rater and the automated algorithm, and 0.84 (CI 0.75-0.89) between the second rater and the automated algorithm. Repeat scan measurement ICCs were 0.91 (CI 0.86-0.94) for the first rater, 0.96 (CI 0.94-0.97) for the second rater, and 0.87 (CI 0.80-0.92) for the automated algorithm. Manual and automated measurements were correlated with drusen area.
  
  
  CONCLUSIONS
  The automated algorithm generally yielded smaller choroidal thickness than the raters with a moderate level of agreement. However, its repeat scan measurement repeatability was comparable to that of the manual measurements. The mean difference between the raters indicated possible biases in different raters and rating sessions. The correlation of the automated measurements with the drusen area was comparable to that of the manual measurements. Automated subfoveal choroidal thickness measurement has potential use in clinical practice and clinical trials, with possibility for reduced time and labor cost.
authors.affiliation: School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, Canada. leeau@sfu.ca
authors.forename: Sieun
authors.initials: S
authors.lastname: Lee
authors.forename: Nader
authors.initials: N
authors.lastname: Fallah
authors.forename: Farzin
authors.initials: F
authors.lastname: Forooghian
authors.forename: Ashley
authors.initials: A
authors.lastname: Ko
authors.forename: Kaivon
authors.initials: K
authors.lastname: Pakzad-Vaezi
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Merkur
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Kirker
authors.forename: David A
authors.initials: DA
authors.lastname: Albiani
authors.forename: Mei
authors.initials: M
authors.lastname: Young
authors.forename: Marinko V
authors.initials: MV
authors.lastname: Sarunic
authors.forename: Mirza Faisal
authors.initials: MF
authors.lastname: Beg
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002829:Choroid / Q000473:pathology; D020256:Choroidal Neovascularization / Q000473:pathology*; D005260:Female; D005584:Fovea Centralis / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards* / Q000706:statistics & numerical data; D008268:Macular Degeneration / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015594:Optic Disk Drusen / Q000473:pathology; D015203:Reproducibility of Results; D012984:Software; D041623:Tomography, Optical Coherence / Q000379:methods* / Q000592:standards* / Q000706:statistics & numerical data