- 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.
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