title: Prevalence and mechanism of appositional angle closure in acute primary angle closure after iridotomy.
abstract: OBJECTIVE
  A prospective observational case series to assess the prevalence of appositional angle closure in darkness among iridotomized Chinese eyes after acute primary angle closure (APAC) with the use of both clinical methods and ultrasound biomicroscopy.
  
  
  METHODS
  Sixteen Chinese patients who had history of APAC and subsequent successful treatment with laser peripheral iridotomy were examined. Fourteen additional control subjects were studied. Gonioscopy and ultrasound biomicroscopic examination were performed in the dark. Gonioscopic appearance of the angle was assessed, and quantitative measurements of the angle from the ultrasound biomicroscopic images were taken.
  
  
  RESULTS
  Of the APAC eyes 55.6% had appositionally closed angle clinically and in 38.9% only Schwalbe's line was visible on gonioscopy. Ultrasound biomicroscopy confirmed structurally different anterior segments between eyes with APAC and the control eyes. In particular, the trabecular-ciliary-process distances were markedly different between the two groups.
  
  
  CONCLUSIONS
  This study documented a high prevalence of appositional closure in iridotomized eyes after APAC in Chinese patients. The anteriorly positioned ciliary body, as documented in these cases by ultrasound biomicroscopy, is the likely mechanism of the angle crowding in this patient population.
authors.affiliation: Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China. ymyeung@ha.org.hk
authors.forename: Barry Y M
authors.initials: BY
authors.lastname: Yeung
authors.forename: Philip W C
authors.initials: PW
authors.lastname: Ng
authors.forename: Thomas Y H
authors.initials: TY
authors.lastname: Chiu
authors.forename: Chi Wai
authors.initials: CW
authors.lastname: Tsang
authors.forename: Felix C H
authors.initials: FC
authors.lastname: Li
authors.forename: Chung Chai
authors.initials: CC
authors.lastname: Chi
authors.forename: Jimmy S M
authors.initials: JS
authors.lastname: Lai
authors.forename: Clement C Y
authors.initials: CC
authors.lastname: Tham
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000208:Acute Disease; D000368:Aged; D002924:Ciliary Body / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000601:surgery*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure; D032801:Iridectomy; D007498:Iris / Q000000981:diagnostic imaging / Q000473:pathology*; D053685:Laser Therapy; D008297:Male; D033401:Microscopy, Acoustic; D011183:Postoperative Complications; D015995:Prevalence; D011446:Prospective Studies; D014129:Trabecular Meshwork / Q000000981:diagnostic imaging / Q000473:pathology*