title: Repeatability and reproducibility of anterior chamber angle measurement with anterior segment optical coherence tomography.
abstract: OBJECTIVE
  To evaluate the repeatability and reproducibility of anterior chamber angle measurement obtained by anterior segment optical coherence tomography.
  
  
  METHODS
  Twenty-five normal subjects were invited for anterior chamber angle imaging with an anterior segment optical coherence tomography (OCT) on one randomly selected eye in three separate visits within a week. Each eye was imaged three times under room light (light intensity = 368 lux) and three times in the dark during the first visit. In the subsequent visits, each eye was imaged once in the light and once in the dark. The angle opening distance (AOD 500) and the trabecular-iris angle (TIA 500) were measured by a single observer. Only the nasal angle was analysed. Intrasession and intersession within-subject standard deviation (Sw), precision (1.96xSw), coefficient of variation (CVw) (100xSw/overall mean), and intraclass correlation coefficient (ICC) were calculated to evaluate repeatability and reproducibility.
  
  
  RESULTS
  For intrasession repeatability, the Sw, precision, CVw and ICC of AOD/TIA were 45 microm/2.4 degrees , 88 microm/4.7 degrees , 5.8%/4.8% and 0.97/0.95 in the light; and 45 microm/2.1 degrees , 88 microm/4.2 degrees , 7.0%/5.0% and 0.98/0.97 in the dark. For intersession reproducibility, the Sw, precision, CVw and ICC of AOD/TIA were 79 microm/3.5 degrees , 155 microm/6.8 degrees , 10.0%/7.0%, 0.91/0.89 in the light; and 64 microm/3.4 degrees , 124 microm/6.6 degrees , 9.9%/7.8% and 0.95/0.92 in the dark.
  
  
  CONCLUSIONS
  The anterior segment OCT demonstrated reliable anterior chamber angle measurement in different lighting conditions with good repeatability and reproducibility.
authors.affiliation: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong
authors.forename: Haitao
authors.initials: H
authors.lastname: Li
authors.forename: Christopher Kai Shun
authors.initials: CK
authors.lastname: Leung
authors.forename: Carol Yim Lui
authors.initials: CY
authors.lastname: Cheung
authors.forename: Lee
authors.initials: L
authors.lastname: Wong
authors.forename: Chi Pui
authors.initials: CP
authors.lastname: Pang
authors.forename: Robert Neal
authors.initials: RN
authors.lastname: Weinreb
authors.forename: Dennis Shun Chiu
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D000867:Anterior Chamber / Q000033:anatomy & histology*; D006801:Humans; D007498:Iris / Q000033:anatomy & histology; D008029:Lighting; D010775:Photic Stimulation / Q000379:methods; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D014129:Trabecular Meshwork / Q000033:anatomy & histology