title: Anterior chamber angle imaging with swept-source optical coherence tomography: measuring peripheral anterior synechia in glaucoma.
abstract: OBJECTIVE
  To investigate the use of swept-source optical coherence tomography (OCT) for measuring the area and degree of peripheral anterior synechia (PAS) involvement in patients with angle-closure glaucoma.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Twenty-three eyes with PAS (detected by indentation gonioscopy) from 20 patients with angle-closure glaucoma (20 eyes had primary angle-closure glaucoma and 3 eyes had angle-closure glaucoma secondary to chronic anterior uveitis [n = 2] and Axenfeld-Rieger syndrome [n = 1]).
  
  
  METHODS
  The anterior chamber angles were evaluated with indentation gonioscopy and imaged by swept-source OCT (Casia OCT, Tomey, Nagoya, Japan) in room light and in the dark using the "angle analysis" protocol, which was composed of 128 radial B-scans each with 512 A-scans (16-mm scan length). The area and degree of PAS involvement were measured in each eye after manual detection of the scleral spur and the anterior irido-angle adhesion by 2 masked observers. The interobserver variability of the PAS measurements was calculated.
  
  
  METHODS
  The agreement of PAS assessment by gonioscopy and OCT, the area and the degree of PAS involvement, and the intraclass correlation coefficient (ICC) of interobserver PAS measurements.
  
  
  RESULTS
  The area of PAS (mean ± standard deviation) was 20.8 ± 16.9 mm(2) (range, 3.9-74.9 mm(2)), and the degree of PAS involvement was 186.5 ± 79.9 degrees (range, 42-314 degrees). There was no difference in the area of PAS (P = 0.90) and the degree of PAS involvement (P = 0.95) between images obtained in room light and in the dark. The interobserver ICCs were 0.99 (95% confidence interval [CI], 0.98-1.00) for the area of PAS and 0.99 (95% CI, 0.97-1.00) for the degree of PAS involvement. There was good agreement of PAS assessment between gonioscopy and OCT images (kappa = 0.79; 95% CI, 0.67-0.91).
  
  
  CONCLUSIONS
  Swept-source OCT allows visualization and reproducible measurements of the area and degree of PAS involvement, providing a new paradigm for evaluation of PAS progression and risk assessment for development of angle-closure glaucoma.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, PR China.
authors.forename: Isabel
authors.initials: I
authors.lastname: Lai
authors.forename: Heather
authors.initials: H
authors.lastname: Mak
authors.forename: Gilda
authors.initials: G
authors.lastname: Lai
authors.forename: Marco
authors.initials: M
authors.lastname: Yu
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
authors.forename: Christopher K S
authors.initials: CK
authors.lastname: Leung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000867:Anterior Chamber / Q000473:pathology*; D000869:Anterior Eye Segment / Q000002:abnormalities; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005124:Eye Abnormalities / Q000150:complications; D015785:Eye Diseases, Hereditary; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis* / Q000209:etiology; D006068:Gonioscopy; D006319:Hearing Loss, Sensorineural / Q000150:complications; D006330:Heart Defects, Congenital / Q000150:complications; D006801:Humans; D007429:Intraocular Pressure; D007499:Iris Diseases / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D000267:Tissue Adhesions / Q000175:diagnosis; D041623:Tomography, Optical Coherence / Q000379:methods*; D014605:Uveitis / Q000150:complications