title: Membrane formation in the chamber angle after failure of argon laser trabeculoplasty: analysis of risk factors.
abstract: OBJECTIVE
  Membrane formation in the chamber angle induced by argon laser trabeculoplasty (ALT) can be a cause of treatment failure. Identification of risk factors for membrane formation was the primary aim of this retrospective study.
  
  
  METHODS
  Semithin sections of trabeculectomy specimens obtained in a 2 year period were examined by light microscopy. 122 eyes which were treated with one or more ALTs before trabeculectomy were identified. In 46 eyes, a sufficient amount of trabecular meshwork was obtained to permit morphological analysis.
  
  
  RESULTS
  Eyes treated with ALT had a significantly higher incidence of membrane formation (p=0.001). In 23/46 specimens a cellular and collagenous membrane was observed covering the entire trabecular meshwork. In 14/23 specimens (61%), this membrane was readily visible at low power magnification (x40). Comparison of these eyes with those without membrane formation revealed a significant difference in the number of ALTs (mean 2.07 (SD 0.73) v 1.48 (0.59); p=0.026) and in preoperative IOP (32.0 (9. 7) v 26.2 (8.4) mm Hg; p=0.04).
  
  
  CONCLUSIONS
  Membrane formation in the chamber angle is a frequent cause of ALT failure. The major risk factor is the number of ALTs performed.
authors.affiliation: Augenklinik, UniversitätsSpital, Zürich, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Koller
authors.forename: J
authors.initials: J
authors.lastname: Stürmer
authors.forename: C
authors.initials: C
authors.lastname: Remé
authors.forename: B
authors.initials: B
authors.lastname: Gloor
mesh_terms: D000368:Aged; D006801:Humans; D053685:Laser Therapy; D008854:Microscopy, Electron; D008875:Middle Aged; D011183:Postoperative Complications / Q000473:pathology*; D012086:Reoperation; D012189:Retrospective Studies; D012307:Risk Factors; D014129:Trabecular Meshwork / Q000473:pathology* / Q000648:ultrastructure; D014130:Trabeculectomy