Filtering Bleb Failure

• Predisposing factors of filtering bleb failure:
  • Previous surgery and resulting subconjunctival fibrosis
  • Aphakia
  • Inflammation
  • Previous filtering bleb failure
  • Long-term medical therapy
  • Neovascular glaucoma
  • Intraoperative complications (e.g. iris or ciliary process incarceration in the trabeculectomy fistula).
• Early signs of a failing filtering bleb:
  • Gradual IOP elevation during the first 2-4 weeks
  • Excessive vascularization of the bleb
  • Flattening of the bleb with the disappearance of microcysts in the bleb
• Retrospective studies have indicated that filtration surgery is more likely to be successful in older patients, patients without African heritage, and those without previous long-term medical therapy.

Management

• Intra- or postoperative anti proliferative therapy (such as 5-fluorouracil or mitomycin-C) to decrease the likelihood of an aggressive postoperative fibroblast-mediated scarring process.
• Sub-tenon's corticosteroid injections may be administered intra- or post-operatively.
• Selective applications of digital pressure to the bleb should also be considered to promote aqueous flow into the subconjunctival space, thereby elevating the filtration bleb.