title: Reproducibility of anterior chamber angle measurements obtained with anterior segment optical coherence tomography.
abstract: OBJECTIVE
  To evaluate the reproducibility of anterior chamber (AC) angle measurements obtained using anterior segment optical coherence tomography (AS-OCT).
  
  
  METHODS
  Patients with suspected glaucoma and those with glaucoma, ocular hypertension, or anatomically narrow angles were recruited from the glaucoma service at the National University Hospital, Singapore. All subjects underwent imaging of the nasal, temporal, and inferior AC angles with an AS-OCT prototype under standardized dark and light conditions. For short-term reproducibility analysis, a single observer acquired two sets of images followed by a third set of images acquired by a second observer. The interval between sessions was 10 minutes. For long-term reproducibility analysis, a single observer acquired two sets of images at least 24 hours apart. Images were measured using custom software to determine the AC depth (ACD), angle opening distance at 500 microm (AOD(500)), angle recess area at 500 microm (ARA(500)), and trabecular-iris space area at 500 microm (TISA(500)). The intraclass correlation coefficient (ICC) was calculated as a measure of intraobserver and interobserver reproducibility.
  
  
  RESULTS
  Twenty eyes of 20 patients were analyzed for short-term reproducibility, and 23 eyes of 23 patients were analyzed for long-term reproducibility. AC depth measurement demonstrated excellent reproducibility (ICC 0.93-1.00) in both dark and light conditions. For the nasal and temporal quadrants, all AC angle parameters demonstrated good to excellent short-term (ICC 0.67-0.90) and long-term (ICC 0.56-0.93) reproducibility in both dark and light conditions. In the inferior quadrant, reproducibility was lower in all categories of analysis and varied from poor to good (ICC 0.31-0.73).
  
  
  CONCLUSIONS
  AS-OCT allows quantitative assessment of the AC angle. The reproducibility of AC angle measurements was good to excellent for the nasal and temporal quadrants. The lower reproducibility of measurements in the inferior quadrant may be unique to this prototype due to difficulty in acquiring high-quality images of the inferior angle. Further assessment of the commercially available AS-OCT is needed to clarify this finding.
authors.affiliation: Wilmer Eye Institute, Baltimore, Maryland, USA.
authors.forename: Sunita
authors.initials: S
authors.lastname: Radhakrishnan
authors.forename: Jovina
authors.initials: J
authors.lastname: See
authors.forename: Scott D
authors.initials: SD
authors.lastname: Smith
authors.forename: Winifred P
authors.initials: WP
authors.lastname: Nolan
authors.forename: Zheng
authors.initials: Z
authors.lastname: Ce
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: David
authors.initials: D
authors.lastname: Huang
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.forename: Paul T K
authors.initials: PT
authors.lastname: Chew
mesh_terms: D000368:Aged; D000867:Anterior Chamber / Q000473:pathology*; D003430:Cross-Sectional Studies; D005901:Glaucoma / Q000473:pathology*; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012846:Singapore; D041623:Tomography, Optical Coherence / Q000592:standards* / Q000706:statistics & numerical data