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.