title: Anterior chamber angle measurement with optical coherence tomography: intraobserver and interobserver variability.
abstract: OBJECTIVE
  To assess intraobserver and interobserver variability of anterior segment optical coherence tomography (AS-OCT) as an objective diagnostic tool to quantify the anterior chamber angle and opening width.
  
  
  METHODS
  University Eye Clinic, Lübeck, Germany.
  
  
  METHODS
  The anterior chamber angle and opening width were assessed in 18 eyes of 9 healthy volunteers by 2 observers. Intraobserver reproducibility was evaluated by calculating an intraclass correlation coefficient (ICC) in a mixed model. Each observer had a separate model using information from 5 scans. Interobserver variability was determined by Bland-Altman analysis. The ICC was calculated in a mixed model using a residual maximum likelihood method. The results of 3 and 5 repeated scans were evaluated to indicate the change to 1 measurement application.
  
  
  RESULTS
  The mean anterior chamber angle measurement was 35.9 degrees +/- 5.7 (SD) for observer A and 36.2 +/- 5.7 degrees for observer B. The ICC was 0.94 and 0.91, respectively. The mean opening width was 315 +/- 62 microm for observer A and 317 +/- 60 microm for observer B. The ICC was 0.97 and 0.93, respectively. Interobserver comparisons showed a mean difference between anterior chamber angle measurements of -0.27 +/- 1.6 degrees, a limit of agreement (LOA) interval from -3.52 to 2.98 degrees, and an ICC estimate of 0.96. The mean difference in opening width measurements was 2.40 +/- 12.40 microm, the LOA from -27.20 to 22.40 microm, and the estimated ICC 0.96. Using 1 instead of the mean of 5 measurements, the LOA range increased by 3.46 degrees for the anterior chamber angle and 30.0 microm for the opening width.
  
  
  CONCLUSIONS
  Anterior chamber angle and opening width measurements by OCT showed low intraobserver and interobserver variability, indicating OCT is a valuable technique for quantitative assessment that provides reproducible measurements and objective documentation by different examiners.
authors.affiliation: Eye Clinic, UK S-H, Campus Lübeck, Lübeck, Germany. mayamueller@gmx.de
authors.forename: Maya
authors.initials: M
authors.lastname: Müller
authors.forename: Gerlinde
authors.initials: G
authors.lastname: Dahmen
authors.forename: Erk
authors.initials: E
authors.lastname: Pörksen
authors.forename: Gerd
authors.initials: G
authors.lastname: Geerling
authors.forename: Horst
authors.initials: H
authors.lastname: Laqua
authors.forename: Andreas
authors.initials: A
authors.lastname: Ziegler
authors.forename: Hans
authors.initials: H
authors.lastname: Hoerauf
mesh_terms: D000328:Adult; D000867:Anterior Chamber / Q000033:anatomy & histology*; D002924:Ciliary Body / Q000033:anatomy & histology*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D014129:Trabecular Meshwork / Q000033:anatomy & histology