title: Reproducibility of anterior segment angle metrics measurements derived from Cirrus spectral domain optical coherence tomography.
abstract: OBJECTIVE
  To investigate the reproducibility of anterior segment angle (ACA) metrics measurements in normal subjects on Cirrus spectral domain optical coherence tomography (SD-OCT).
  
  
  METHODS
  40 eyes from 20 healthy, normal subjects underwent anterior segment imaging using a Cirrus SD-OCT. For each eye, 2 acquisitions of 5-line raster scans were performed perpendicularly on the inferior (270 degrees) angle. The Schwalbe's line-angle opening distance (SL-AOD) and Schwalbe's line-trabecular-iris space area (SL-TISA) measurements were performed by masked certified reading center graders using customized grading software. Intra-acquisition, intergrader, and intragrader reproducibility of SL-AOD and SL-TISA measurements were evaluated by intraclass correlation coefficients (ICC), Bland-Altman plots, and computation of mean percent difference (MPD) and coefficient of variability (CV).
  
  
  RESULTS
  The mean SL-AOD (average of 2 acquisitions) was 0.75 mm (range, 0.32 mm to 1.39 mm); SL-TISA was 0.28 mm² (range, 0.082 mm² to 0.569 mm²). The repeatability of Cirrus SD-OCT was excellent for both SL-AOD (MPD 4.74%, CV=0.92, ICC=0.99) and SL-TISA (MPD 9.4%, CV=0.8, ICC=0.99). The intragrader reproducibility was high for SL-AOD (MPD 4.28%, CV=0.94, ICC=0.995) and SL-TISA (MPD 6.05%, CV=0.89, ICC=0.993). The inter-grader reproducibility was not as good but still excellent for both SL-AOD (MPD 15.47%, CV=0.95, ICC=0.94) and SL-TISA (MPD 19.43%, CV=0.99, ICC=0.93). Bland-Altman plots of all comparisons did not demonstrate any apparent bias, with similar repeatability at various SL-AOD and SL-TISA values.
  
  
  CONCLUSIONS
  In our population of young healthy adults with normal eyes, there was excellent intra-acquisition, intragrader, and intergrader reproducibility for Schwalbe's line-based ACA metrics obtained from Cirrus SD-OCT images. These SD-OCT-derived measures may serve as reliable descriptors of angle morphometry for use in clinical trials and clinical practice.
authors.affiliation: *Doheny Image Reading Center, Doheny Eye Institute ‡Department of Ophthalmology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA †The Affiliated Hospital of Medical College, Qingdao University, Qingdao, Shandong, P.R. China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Pan
authors.forename: Ken
authors.initials: K
authors.lastname: Marion
authors.forename: Jyotsna
authors.initials: J
authors.lastname: Maram
authors.forename: Zhou Yuan
authors.initials: ZY
authors.lastname: Zhang
authors.forename: Brian A
authors.initials: BA
authors.lastname: Francis
authors.forename: Muneeswar G
authors.initials: MG
authors.lastname: Nittala
authors.forename: Srinivas R
authors.initials: SR
authors.lastname: Sadda
authors.forename: Vikas
authors.initials: V
authors.lastname: Chopra
mesh_terms: D000328:Adult; D000869:Anterior Eye Segment / Q000033:anatomy & histology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult