Encapsulated Blebs: Is Needling the Best Bet for Glaucoma Relief?
"A head-to-head study reveals how a minimally invasive revision technique stacks up against traditional medication for glaucoma-related bleb encapsulation."
Glaucoma, a condition characterized by progressive visual field defects, demands effective management of intraocular pressure (IOP). While medication often serves as the first line of defense, surgical intervention becomes necessary when medical treatments fall short. Trabeculectomy, a surgical procedure, remains a gold standard among specialists. However, its long-term success hinges on meticulous post-operative care, particularly in addressing early signs of bleb failure.
Bleb failure, often resulting from scarring under or over the scleral flap, can lead to encapsulated blebs—Tenon's capsule cysts—that compromise filtration. These encapsulated blebs can occur anytime after the initial surgery. Transconjunctival needling revision (TNR) emerges as a minimally invasive technique to restore filtration by disrupting fibrotic tissue. The effectiveness of TNR can be enhanced with antifibrotic agents like 5-fluorouracil (5-FU) or mitomycin C (MMC).
In light of these challenges, researchers have explored medical treatment (MT) with topical hypotensive medications as an alternative for managing encapsulated blebs. Studies evaluating various success rates have considered factors such as target pressure, bleb morphology, the timing of the needling procedure, the number of procedures performed, and the use of antifibrotic agents. This article delves into a prospective study comparing early TNR with 5-FU to MT in eyes with encapsulated blebs, providing valuable insights for ophthalmologists and patients alike.
Needling and Surgical Revision
After trabeculectomy with mitomycin C, encapsulated blebs may be managed with bleb needling alone or with needling plus transconjunctival scleral flap sutures. The PLOS ONE study compared these two approaches over long-term follow-up, including their effects on intraocular pressure and glaucoma progression in 46 patients. A reported clinical case also illustrates that intraocular pressure can rise after an initially successful postoperative result, while structured bleb assessment considers vascularity, encapsulation, microcysts, and bleb morphology.
Needling vs. Medication: Which Approach Wins for Encapsulated Blebs?
A study published in Clinics (2013) explored and compared the short-term efficacy of early TNR with 5-FU to medical treatment in eyes with encapsulated blebs and uncontrolled IOP after trabeculectomy. The prospective, randomized interventional study included 40 eyes of 39 patients with encapsulated blebs developed within five months or less after primary trabeculectomy with MMC and IOP ≥ 20 mmHg. Participants were treated at the Hospital das Clínicas of the University of São Paulo, Brazil.
- TNR with 5-FU Protocol: A 27-gauge needle was used to enter the subconjunctival space, disrupt scar tissue, and reestablish aqueous flow. Following this, 5 mg of 5-FU was injected subconjunctivally.
- Post-Operative Care: Patients received topical antibiotics and steroids, with steroid tapering guided by clinical response.
- Medical Treatment (MT) Protocol: Topical hypotensive treatment was initiated, beginning with a nonspecific beta-blocker and/or prostaglandin, followed by carbonic anhydrase inhibitors and/or selective alpha agonists as needed.
- Exclusion Criteria: Patients requiring further surgical procedures were excluded to maintain the integrity of the comparison.
Evidence for Bleb Needling
A 2020 systematic review and meta-analysis found that baseline intraocular pressure before bleb needling helped explain variation among study results. Its metaregression reported a statistically significant trend in which higher baseline intraocular pressure was associated with a greater reduction after needling, with p < 0.001. Other reviewed material describes bleb needling as a simple, minimally invasive, extraocular procedure, while a separate study specifically examined needling revision with adjunctive 5-fluorouracil in 16 eyes of 15 subjects after unsuccessful trabeculectomy.
Limits of the Evidence
Evidence for early transconjunctival needling revision with 5-fluorouracil versus medical treatment comes from a 12-month prospective study of encapsulated blebs. The study authors identified a small sample size as a limitation. They also identified the short follow-up period as a limitation, leaving uncertainty about longer-term outcomes.
Bleb-Based Comparisons
A comparative study examined the histopathologic and morphologic features of encapsulated blebs after Ahmed glaucoma valve implantation and standard trabeculectomy with mitomycin C. The cited Tube Versus Trabeculectomy study reported that trabeculectomy success after phacoemulsification was worse. Because ab externo MIGS creates a sub-Tenon bleb similar to that created by trabeculectomy, the source considers it reasonable to question whether Preserflo implantation could be affected by similar factors.
The Verdict: TNR with 5-FU Offers Promising IOP Control
The study's findings suggest that while both TNR with 5-FU and MT can effectively manage encapsulated blebs, TNR offers a significant advantage in achieving lower mean IOP at the 12-month follow-up. The inclusion of only encapsulated blebs enhanced the accuracy of the study, minimizing variability due to morphological differences. This suggests that TNR with adjunctive 5-FU, without further medical therapy, is highly effective in maintaining successful IOP control for at least 12 months.
Fibrosis and Implant Failure
Encapsulated bleb excision with collagen matrix implantation was studied in 18 eyes of 18 patients whose Ahmed glaucoma valve implantation had failed. The study evaluated patients whose intraocular pressure was not controlled by conservative treatment after failure of an implanted Ahmed glaucoma valve. The Advanced Glaucoma Intervention Study reported that four-week postoperative mean intraocular pressure was higher in eyes with an encapsulated bleb, although the two groups' means converged after one year when medical treatment was resumed.
Recurrent Disease in Difficult Cases
A 2022 case report described an early adolescent boy with primary congenital glaucoma, a prior glaucoma drainage device implantation, maximum medical therapy, and a recurrent encapsulated bleb. The report emphasized that childhood glaucoma remains a challenging surgical disease worldwide despite advances in surgical management. The case involved an Ahmed glaucoma valve history and swelling in the superotemporal orbital region, illustrating how recurrent bleb problems can occur in patients with multiple failed glaucoma surgeries.