title: Comparison of gonioscopy and anterior segment ocular coherence tomography in detecting angle closure in different quadrants of the anterior chamber angle.
abstract: OBJECTIVE
  To compare the performance of gonioscopy and anterior segment (AS) optical coherence tomography (OCT) in detecting angle closure in the different quadrants of the anterior chamber angle (ACA).
  
  
  METHODS
  Cross-sectional observational study.
  
  
  METHODS
  Five hundred two consecutive subjects more than 50 years of age with no previous ophthalmic problems recruited from a community clinic in Singapore.
  
  
  METHODS
  All subjects underwent gonioscopy and AS OCT imaging in the dark. Using gonioscopy, the ACA was graded using the Scheie system by a single examiner masked to AS OCT findings.
  
  
  METHODS
  The ACA in a particular quadrant was classified as closed if the posterior trabecular meshwork could not be seen on gonioscopy. A closed ACA on AS OCT imaging was defined by the presence of any contact between the iris and angle wall anterior to the scleral spur.
  
  
  RESULTS
  After excluding eyes with poor image quality, a total of 423 right eyes were included in the analysis. A closed angle in at least 1 quadrant was observed in 59% of the eyes by AS OCT and in 33% of the eyes by gonioscopy (P<0.001), with fair agreement between the two methods (kappa = 0.40). The frequency of closed angles by AS OCT and gonioscopy were 48% versus 29% superiorly, 43% versus 22% inferiorly, 18% versus 14% nasally, and 12% versus 20% temporally, respectively. Of the 119 of 1692 quadrants that were closed on gonioscopy but open on AS OCT, a steep iris profile was present in 61 (51%) of 119 quadrants on AS OCT, and of the 276 of 1692 quadrants that were open on gonioscopy but closed on AS OCT, 196 (71%) of 276 quadrants showed short iridoangle contact on AS OCT.
  
  
  CONCLUSIONS
  The highest rates of closed angles on gonioscopy and AS OCT images were observed in the superior quadrant. Anterior segment OCT tended to detect more closed ACAs than gonioscopy, particularly in the superior and inferior quadrants. Variations in the iris profile and level of iridoangle contact also may explain some of the differences seen between gonioscopy and AS OCT.
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Center, Singapore.
authors.forename: Lisandro M
authors.initials: LM
authors.lastname: Sakata
authors.forename: Raghavan
authors.initials: R
authors.lastname: Lavanya
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Han T
authors.initials: HT
authors.lastname: Aung
authors.forename: Hong
authors.initials: H
authors.lastname: Gao
authors.forename: Rajesh S
authors.initials: RS
authors.lastname: Kumar
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Foster
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000869:Anterior Eye Segment / Q000473:pathology*; D003315:Cornea / Q000473:pathology; D003430:Cross-Sectional Studies; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis*; D006068:Gonioscopy / Q000379:methods*; D006801:Humans; D007429:Intraocular Pressure; D007498:Iris / Q000473:pathology; D008297:Male; D008875:Middle Aged; D041623:Tomography, Optical Coherence / Q000379:methods*; D014065:Tonometry, Ocular; D014129:Trabecular Meshwork / Q000473:pathology