title: Repeatability and reproducibility of choroidal vessel layer measurements in diabetic retinopathy using enhanced depth optical coherence tomography.
abstract: OBJECTIVE
  To describe novel segmentation protocols for choroidal layers, Sattler's medium and Haller's large vessel layers, using enhanced depth imaging optical coherence tomography (EDI-OCT), and to examine the repeatability and reproducibility of these measurements in eyes with diabetic retinopathy.
  
  
  METHODS
  Fifty-one patients with Type 2 diabetes mellitus were imaged using custom EDI scanning protocols. Detailed segmentation was performed to quantify the retina, choroid, Haller's large, and Sattler's medium vessel layers in the total macular circle (TMC) and foveal central subfield (FCS). The coefficient of repeatability (CR) and intraclass correlation coefficient (ICC) were used as a measure of repeatability and relative reliability within graders. Reproducibility or interobserver variability was assessed using Bland-Altman plots and 95% limits of agreement (LoA).
  
  
  RESULTS
  Intragrader CR of the retina, choroid, Sattler's, and Haller's layers for thickness measurements were 19.2, 26.9, 35.2, and 29.2 μm, respectively. Intergrader 95% LoA were 27.9, 41.5, 38.6, 31.1 μm (thickness), respectively. Choroidal sublayer measurements showed good intraobserver reliability (ICC 0.78-0.98). Interobserver variability for retinal and choroidal measurements was not significantly different (P > 0.45). Measurements from the TMC showed slightly better repeatability and agreement compared with the FCS alone. Mean intergrader differences were reduced after training, and were most apparent in choroidal sublayers.
  
  
  CONCLUSIONS
  The choroidal vascular sublayers can be quantified with good reliability, repeatability, and reproducibility. Accurate quantitative assessment of these sublayers may provide new insights into the role of the choroid in visual loss in patients with diabetic retinopathy, and prove useful for future clinical trials.
authors.affiliation: Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
authors.forename: Dawn A
authors.initials: DA
authors.lastname: Sim
authors.forename: Pearse A
authors.initials: PA
authors.lastname: Keane
authors.forename: Hemal
authors.initials: H
authors.lastname: Mehta
authors.forename: Simon
authors.initials: S
authors.lastname: Fung
authors.forename: Javier
authors.initials: J
authors.lastname: Zarranz-Ventura
authors.forename: Marcus
authors.initials: M
authors.lastname: Fruttiger
authors.forename: Praveen J
authors.initials: PJ
authors.lastname: Patel
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Egan
authors.forename: Adnan
authors.initials: A
authors.lastname: Tufail
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002829:Choroid / Q000473:pathology; D015862:Choroid Diseases / Q000473:pathology*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D003930:Diabetic Retinopathy / Q000473:pathology*; D005260:Female; D005584:Fovea Centralis / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods* / Q000592:standards* / Q000706:statistics & numerical data