title: Appositional closure identified by ultrasound biomicroscopy in population-based primary angle-closure glaucoma suspects: the Liwan eye study.
abstract: OBJECTIVE
  To describe the characteristics of the iridocorneal angle using ultrasound biomicroscopy (UBM) in Chinese people classified gonioscopically as having suspected primary angle-closure (PACS) glaucoma.
  
  
  METHODS
  PACS were defined as not having visible posterior (usually pigmented) trabecular meshwork in two or more quadrants examined by static gonioscopy. The PACS and 1 of 10 those who did not meet this criterion were identified from a population-based survey. Iridotrabecular meshwork contact (ITC) was identified and further classified into low and high, according to standard UBM images. Those with high ITC were further classified according the configuration of ITC: B-type, with contiguous ITC from the base of the angle, and S-type, with ITC localized to the region of Schwalbe's line.
  
  
  RESULTS
  ITC was identified in 78.6% of the superior, 40.2% of the nasal, 59.8% of the inferior, and 25.6% of the temporal quadrants in the PACS (n = 117). These proportions were 43.9%, 15.8%, 29.8%, and 14.0% in the controls (n = 57), respectively. About two thirds of the eyes with ITC were classified as high. In those with high ITC, the number with B- and S-type ITC was very similar. The proportions of any high ITCs increased substantially from 15.4% in those with Shaffer angle grade 4 and 45.0% in grade 3, to 71.0% in grade 2, 70.2% in grade 1, and 86.4% in grade 0.
  
  
  CONCLUSIONS
  More ITC is identified on UBM imaging than by gonioscopy. Careful consideration should be given to the assessment modality regarded as the reference standard in defining anatomic risk factors for glaucomatous visual loss and the need for treatment.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Xiangbin
authors.initials: X
authors.lastname: Kong
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Foster
authors.forename: Qunxiao
authors.initials: Q
authors.lastname: Huang
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Zheng
authors.forename: Wenyong
authors.initials: W
authors.lastname: Huang
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Cai
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People / Q000706:statistics & numerical data; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000000981:diagnostic imaging* / Q000453:epidemiology; D006068:Gonioscopy; D006306:Health Surveys; D006801:Humans; D008297:Male; D033401:Microscopy, Acoustic / Q000592:standards*; D008875:Middle Aged; D012015:Reference Standards; D012307:Risk Factors; D014786:Vision Disorders / Q000000981:diagnostic imaging* / Q000208:ethnology