title: Is post-trabeculectomy hypotony a risk factor for subsequent failure? A case control study.
abstract: BACKGROUND
  Ocular hypotony results in an increased break down of the blood-aqueous barrier and an increase in inflammatory mediator release. We postulate that this release may lead to an increased risk of trabeculectomy failure through increased bleb scarring. This study was designed to try to address the question if hypotony within one month of trabeculectomy for Primary Open Angle Glaucoma (POAG), is a risk factor for future failure of the filter.
  
  
  METHODS
  We performed a retrospective, case notes review, of patients who underwent trabeculectomy for POAG between Jan 1995 and Jan 1996 at our hospital. We identified those with postoperative hypotony within 1 month of surgery. Hypotony was defined as an intraocular pressure (IOP) < 8 mmHg or an IOP of less than 10 mmHg with choroidal detachment or a shallow anterior chamber. We compared the survival times of the surgery in this group with a control group (who did not suffer hypotony as described above), over a 5 year period. Failure of trabeculectomy was defined as IOP > 21 mmHg, or commencement of topical antihypertensives or repeat surgery.
  
  
  RESULTS
  97 cases matched our inclusion criteria, of these 38 (39%) experienced hypotony within 1 month of surgery. We compared the survival times in those patients who developed hypotony with those who did not using the log-rank test. This data provided evidence of a difference (P = 0.0492) with patients in the hypotony group failing more rapidly than the control group.
  
  
  CONCLUSIONS
  Early post-trabeculectomy hypotony (within 1 month) is associated with reduced survival time of blebs.
authors.affiliation: Sunderland Eye Infirmary, Queen Alexandra Road, Sunderland, SR2 9HP, UK. sarah.benson@moorfields.nhs.uk
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Benson
authors.forename: Kaveri
authors.initials: K
authors.lastname: Mandal
authors.forename: Catey V
authors.initials: CV
authors.lastname: Bunce
authors.forename: Scott G
authors.initials: SG
authors.lastname: Fraser
mesh_terms: D016022:Case-Control Studies; D005902:Glaucoma, Open-Angle / Q000601:surgery*; D006801:Humans; D007429:Intraocular Pressure; D015814:Ocular Hypotension / Q000209:etiology*; D011183:Postoperative Complications; D012189:Retrospective Studies; D012307:Risk Factors; D014130:Trabeculectomy; D017211:Treatment Failure