Baerveldt Versus Paul Study

Background and Rationale:

Glaucoma is a leading cause of irreversible blindness. Reduction of intraocular pressure (IOP) is the only proven modifiable factor for slowing glaucoma progression. Glaucoma drainage devices are commonly used when glaucoma is inadequately controlled with medical or laser treatment and when other glaucoma procedures are considered likely to fail.

The 350-mm² Baerveldt Glaucoma Implant (BGI) is an established non-valved glaucoma drainage device with demonstrated efficacy and safety in previous randomised clinical trials. The Paul Glaucoma Implant (PGI) is a newer non-valved device that uses a smaller-diameter tube. The PGI has been proposed to provide improved early postoperative IOP control and potentially reduce complications such as hypotony, corneal endothelial damage and tube exposure. However, these potential advantages have not been established in a prospective randomised comparison with the BGI. Existing comparative evidence is primarily retrospective and has not demonstrated a clear difference between the devices.

The Baerveldt versus Paul Study is designed to address this uncertainty by directly comparing the long-term safety and effectiveness of the BGI and PGI in patients requiring glaucoma drainage device surgery.

Study Design:

This is a multicentre, Phase 4, pragmatic, registry-based randomised controlled trial with five years of postoperative follow-up. Eligible study eyes will be randomised in a 1:1 ratio to implantation of either a 350-mm² Baerveldt Glaucoma Implant or a Paul Glaucoma Implant. Both devices are established treatments used in routine glaucoma care. Neither participants nor treating investigators will be masked to treatment allocation.

Randomisation will use randomly permuted blocks of variable size and will be stratified by clinical centre and glaucoma type. Glaucoma-type strata will include primary glaucoma or ocular hypertension, secondary glaucoma excluding uveitic and neovascular glaucoma, neovascular glaucoma, and uveitic glaucoma.

The trial will be conducted using the Fight Glaucoma Blindness! Registry within the Save Sight Registries platform. The registry-based design will support participant enrolment, collection of baseline and postoperative clinical data, monitoring of follow-up completeness, central data-quality checks, safety surveillance and statistical analysis. This approach is intended to integrate trial procedures into routine clinical care while maintaining the methodological safeguards of a randomised controlled trial.

Implantation will be performed in accordance with the study protocol. Accepted variations in surgical technique, including methods of tube occlusion, use of intraluminal stents or fenestrations and patch-graft material, may be selected by the operating surgeon and will be recorded prospectively in the registry.

Outcomes and Follow-up:

The principal objective is to compare surgical success and failure between the two treatment groups. Surgical failure is defined as IOP greater than 21 mmHg or less than 6 mmHg on two consecutive visits more than three months after surgery; less than a 20% reduction in IOP from baseline on two consecutive visits more than three months after surgery; additional glaucoma surgery; loss of light-perception vision; or removal of the implant for any reason.

Eyes that have not met a failure criterion and do not require glaucoma medication will be classified as complete successes. Eyes that have not failed but require supplemental glaucoma medication will be classified as qualified successes.

Additional outcomes will include IOP, number of glaucoma medications, visual acuity, visual-field outcomes, glaucoma reoperations, and intraoperative and postoperative complications. Safety outcomes will include hypotony, choroidal effusion, suprachoroidal haemorrhage, endophthalmitis, corneal oedema, tube or implant erosion, tube malposition, diplopia and other device- or procedure-related complications.

Follow-up is scheduled at postoperative day 1; week 1; months 1, 3, 6, 12 and 18; and annually from years 2 through 5. An independent Data and Safety Monitoring Board will review accumulating safety data, trial conduct and prespecified interim analyses.

Inclusion criteria

• Age ≥ 18 years of age
• Glaucoma that is inadequately controlled on tolerated medical therapy with intraocular pressure greater than or equal to 16 mm Hg.
• An aqueous shunt implant as planned surgical procedure
• A diagnosis of ocular hypertension, primary open angle glaucoma, primary angle closure glaucoma, or secondary glaucoma.

Exclusion criteria

• Unwilling or unable to give consent, unwilling to accept randomization, or unable to return for scheduled protocol visits.
• Pregnant or nursing women.
• No light perception vision.
• Uveitis secondary to Juvenile Idiopathic Arthritis
• Previous cyclodestructive procedure or previous aqueous shunt device implanted in the same eye
• Supero-temporal buckling or other external impediment to supero-temporal aqueous shunt implantation
• Silicone oil-filled eyes or sufficient residual intraocular silicone oil to preclude supero-temporal aqueous shunt implantation
• Vitreous present in the anterior chamber, sufficient to require a vitrectomy at the time of surgery
• Condition with high episcleral pressure, such as Sturge-Weber or nanophthalmos
• Acute trauma (within 3 months)
• Need for glaucoma surgery combined with other ocular procedures (i.e. cataract surgery, penetrating keratoplasty, or retinal surgery) or anticipated need for additional ocular surgery.