Over my 11 years in practice, I have watched glaucoma management evolve significantly. Minimally invasive glaucoma surgery (MIGS) has offered safer alternatives to traditional filtering surgery, but a gap has persisted. What do we offer patients who need more pressure reduction than angle-based MIGS provides but who are not ideal candidates for filtering surgery?
The reemergence of uveoscleral outflow enhancement, now supported by bio-interventional technology such as AlloFlo Uveo (Iantrek), presents a meaningful solution. By accessing the uveoscleral pathway via cyclodialysis that is reinforced with a homologous, biocompatible implant, we may achieve pressure reduction through an anatomically distinct route while preserving a favorable safety profile.
Learning from History
Those of us who used the CyPass micro-stent (Alcon) understand both the promise and caution of supraciliary intervention. Studies showed approximately 30% IOP lowering, but the device was withdrawn in 2018 due to endothelial cell loss concerns identified in 5-year follow-up data.
That experience taught us valuable lessons: The supraciliary space offers genuine therapeutic potential, but long-term safety requires careful attention. Modern iterations of uveoscleral enhancement incorporate those lessons by using biomaterials rather than permanent synthetic devices, aiming to stabilize the cleft without introducing rigid structures that could threaten the endothelium over time.
Understanding the Gap
Angle-based MIGS procedures generally offer a good safety profile and meaningful pressure reduction. Meta-analyses demonstrate that combined phacoemulsification with MIGS achieves significant IOP reduction, with trabecular meshwork bypass and goniotomy procedures lowering IOP to the mid-teens without increasing sight-threatening events.
Traditional filtering surgeries achieve dramatic pressure reduction. The Tube Versus Trabeculectomy Study demonstrated mean IOPs of 14.4 mm Hg with tube shunts and 12.6 mm Hg with trabeculectomy at 5 years. However, hypotony following trabeculectomy occurs in 1% to 18% of cases compared with 2.9% with earlier supraciliary devices.
Previously, for management of glaucoma progression, we would maximize medical therapy, repeat angle procedures and, if neither of these options was effective, then proceed to filtering surgery. A less invasive option that accesses a different physiological pathway offers a needed intermediate step.
Why Multiple Pathways Matter
The eye has two primary outflow pathways: conventional outflow through Schlemm’s canal and uveoscleral outflow through the supraciliary space. The conventional pathway handles approximately 75% to 85% of aqueous drainage, with the trabecular meshwork contributing most outflow resistance. Most surgical interventions have focused here, meaning multiple procedures targeting the same anatomical space.
When we have optimized trabecular-based outflow and need additional reduction, access to a different pathway becomes crucial. This preserves future options while optimizing natural drainage rather than bypassing it.
Clinical Applications with AlloFlo Uveo
In early experience with AlloFlo Uveo, several scenarios have emerged in which uveoscleral enhancement fills critical needs. Post-angle procedure patients who achieved good but insufficient reduction gain a logical next step before filtering surgery. Pre-filtering surgery candidates may delay or avoid more invasive intervention.
Combination with tube shunts has proven valuable for patients requiring very low pressures. Tube shunts typically equilibrate around physiologic episcleral venous pressure. By combining them with uveoscleral enhancement, very low pressures difficult to obtain otherwise have been achieved.
Technical Considerations
The technique’s accessibility matters. The procedure builds naturally on skills most anterior segment surgeons possess. Visualization remains critical. When minor bleeding occurs during cleft creation, instilling additional viscoelastic clears the view. Patient feedback provides crucial information; if patients exhibit signs of discomfort, reassessment of the landmarks and tissue plane is important.
The scleral spur serves as a guide. After instilling viscoelastic, tracing it posteriorly, looking for a consistent, unbroken band of white tissue is helpful. Methodical technique matters more than speed initially.
The learning curve appears modest for surgeons who are comfortable with other MIGS procedures.
Safety and Patient Selection
Modern uveoscleral enhancement differs significantly from earlier iterations. Using homologous, biocompatible allograft material for cleft reinforcement may help mitigate some of the endothelial concerns identified with rigid supraciliary implants.
Hypotony has not been a concern in early experience, unlike filtering surgery in which it occurs in 1% to 18% of cases. Visual recovery mirrors that of other MIGS procedures.
This approach is avoided in patients with uveitic glaucoma, extensive anterior segment fibrosis, neovascular glaucoma or poor gonioscopic visibility. For patients with reasonable anatomy and no significant uveitis history, the technique appears broadly applicable.
In early experience, the safety profile has been encouraging, showing low rates of hypotony, absence of endothelial cell complications to date and predictable postoperative courses. Ongoing data collection remains critical and will further refine patient selection.
Talking About Uveoscleral Outflow Enhancement
Ensuring that patients understand that glaucoma surgeries help prevent vision loss but do not improve it remains challenging, but the ability to explain that we are activating a different drainage pathway than previously addressed has been valuable.
Accessible terms such as “opening a new drainage route” or “diverting flow to a different natural space in the eye” are helpful. For patients facing potential filtering surgery, the contrast in safety profiles makes this an appealing earlier option.
Distinguishing between procedures that “optimize your body’s natural pathways” vs. Those that “bypass your body’s natural pathways” helps patients understand treatment rationale.
Looking Forward
The reemergence of uveoscleral outflow enhancement with biomaterial-based implants validates the multi-pathway approach in glaucoma management. We no longer need to concentrate all surgical efforts on a single anatomical space.
Accessibility matters. The learning curve appears manageable for surgeons comfortable with MIGS procedures.
Combining uveoscleral enhancement with other procedures opens new possibilities, allowing us to layer interventions across different pathways rather than immediately using aggressive options.
Conclusion
Uveoscleral outflow enhancement fills a genuine gap, providing an option between trabecular-based MIGS and filtering surgery. It offers a different anatomical target when angle procedures prove insufficient and enables combination approaches that can achieve very low pressures with acceptable safety.
After 11 years in practice, I value tools that genuinely expand what we can offer patients. Bio-interventional uveoscleral enhancement complements existing procedures, maintains physiologic flow pathways and addresses previously underserved clinical needs with encouraging safety and efficacy signals.
As we accumulate longer-term data, we will continue to refine our understanding of where this approach fits optimally. For now, I am grateful to have another pathway to help my patients maintain their vision and quality of life.
- For more information:
- Douglas McGraw, DO, can be reached at drmcgraw@ridgeeyecare.com.
