Filtering Bleb Failure

Scarred filtering bleb with absence of conjunctival microcysts.
  • 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.


  • 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.
Flat filtering bleb with absence of conjunctival microcysts.