title: Investigation of the variability of anterior chamber scan protocol with Cirrus high definition optical coherence tomography.
abstract: OBJECTIVE
  The evaluation of anterior chamber scan of Cirrus optical coherence tomography for routine clinical use.
  
  
  BACKGROUND
  To assess the variability of anterior chamber angle measurements.
  
  
  METHODS
  This was a cross-sectional study.
  
  
  METHODS
  Forty subjects aged 40-80 years were included.
  
  
  METHODS
  One randomly selected eye from 40 subjects was imaged with Cirrus optical coherence tomography (Carl Zeiss Meditec, Dublin, CA) by two different operators (expert vs. non-expert) with a 15-min interval for inter-observer and intra-observer variability of image acquisition. For image grading, the angle opening distance (AOD750) and the trabecular iris space area (TISA750) of nasal and temporal quadrants were measured with a customized algorithm (ImageJ, NIH, Bethesda, MD) by two different graders in a masked and random fashion. Bland Altman analysis and intraclass correlation coefficient (ICC) were calculated.
  
  
  METHODS
  ICC and limit of agreements (LOA).
  
  
  RESULTS
  There were 15 (37.5%) eyes with closed angles. For inter-observer variability, the mean difference (95% LOA) of AOD750 for image acquisition and grading were -0.0039 mm (-0.0486, 0.0408) and 0.0011 mm (-0.0228, 0.025), respectively. The mean difference (95% LOA) of AOD750 for intra-observer variability for image acquisition and grading were 0.0013 mm (-0.0362, 0.0389) and -0.0013 mm (-0.0482, 0.0457), respectively. The ICCs were all ≥0.9. There was no significant difference in measurement variability between open and closed angles (P > 0.05).
  
  
  CONCLUSIONS
  Anterior chamber scan had low inter-observer and intra-observer variability in quantitative evaluation that was not affected by the angle status or the experience of an operator.
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.
authors.forename: Tin A
authors.identifier: http://orcid.org/0000-0001-7649-6952
authors.initials: TA
authors.lastname: Tun
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Shayne S
authors.initials: SS
authors.lastname: Tan
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.
authors.forename: Eray
authors.initials: E
authors.lastname: Atalay
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.
authors.forename: Sushma
authors.initials: S
authors.lastname: Verma
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.|Duke-NUS Graduate Medical School, National University of Singapore, Singapore.
authors.forename: Monisha E
authors.initials: ME
authors.lastname: Nongpiur
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.|Duke-NUS Graduate Medical School, National University of Singapore, Singapore.
authors.forename: Mani
authors.initials: M
authors.lastname: Baskaran
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.|Yong Loo Lin School of Medicine, National University of Singapore, Singapore.|Duke-NUS Graduate Medical School, National University of Singapore, Singapore.
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.|Duke-NUS Graduate Medical School, National University of Singapore, Singapore.
authors.forename: Rahat
authors.initials: R
authors.lastname: Husain
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000867:Anterior Chamber / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: angle opening distance; anterior chamber angle; spectral-domain optical coherence tomography; variability