title: A prospective ultrasound biomicroscopy evaluation of changes in anterior segment morphology after laser iridotomy in Asian eyes.
abstract: OBJECTIVE
  To prospectively quantify changes in anterior segment morphology after laser iridotomy using gonioscopy and ultrasound biomicroscopy (UBM).
  
  
  METHODS
  Prospective comparative observational case series.
  
  
  METHODS
  Fifty-five fellow eyes of patients presenting with acute primary angle closure (APAC).
  
  
  METHODS
  The fellow eyes of patients presenting with APAC were examined with UBM, A-scan ultrasonography, and optical pachymetry at presentation and 2 weeks after sequential argon/neodymium yttrium-aluminum-garnet laser peripheral iridotomy (LPI). UBM images were analyzed using UBM Pro 2000 software. Baseline measurements were made both under standard lighting conditions and in darkness to look for changes in anterior segment findings.
  
  
  METHODS
  The degree of angle opening was measured using the angle-opening distance (AOD) at 250 and 500 microm from the scleral spur (AOD250 and AOD500, respectively) and angle recess area (ARA).
  
  
  RESULTS
  Fifty-five Asian patients were examined; AOD250, AOD500, and ARA all significantly increased after sequential laser iridotomy (P < 0.002). Gonioscopic grading of the angle opening significantly increased in all 4 quadrants (P < 0.001). The Van Herick grade of limbal anterior chamber depth increased (P < 0.001), whereas the number of eyes classified as occludable decreased (73%-33%, P < 0.001). Anterior chamber depth did not change significantly (2.41 mm +/- 0.28 mm vs. 2.42 mm +/- 0.30 mm, P = 0.43) as measured with optical pachymetry. Increased illumination increased the angle-opening measures, but induced a different alteration in peripheral iris morphology. Illumination-induced changes were greater after iridotomy than before laser treatment.
  
  
  CONCLUSIONS
  In Asian eyes at high risk of developing APAC, sequential LPI produced a significant widening of the anterior chamber angle without deepening the anterior chamber centrally. LPI produces changes in iris morphology that are different from those caused by an increase in illumination, indicating that different mechanisms account for angle opening under these 2 conditions.
authors.affiliation: Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore 168751, Singapore.
authors.forename: Gus
authors.initials: G
authors.lastname: Gazzard
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Joe G
authors.initials: JG
authors.lastname: Devereux
authors.forename: Paul
authors.initials: P
authors.lastname: Chew
authors.forename: Steve K L
authors.initials: SK
authors.lastname: Seah
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000869:Anterior Eye Segment / Q000000981:diagnostic imaging*; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000000981:diagnostic imaging* / Q000208:ethnology / Q000601:surgery*; D006068:Gonioscopy; D006801:Humans; D032801:Iridectomy / Q000379:methods*; D007498:Iris / Q000000981:diagnostic imaging* / Q000601:surgery; D053685:Laser Therapy; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012846:Singapore / Q000453:epidemiology; D014463:Ultrasonography