XEN Gel Stent vs Trabeculectomy: An In-Depth Comparison

Glaucoma, a leading cause of irreversible blindness, often requires surgical intervention when medications and laser treatments fail to control intraocular pressure (IOP). The XEN Gel Stent and trabeculectomy are two widely used procedures designed to enhance aqueous humor drainage and reduce IOP. Each method has distinct techniques, risks, and outcomes, making it essential for patients and clinicians to understand their differences.

Examining these procedures reveals variations in implantation, fluid regulation, and tissue responses that influence long-term success.

XEN Gel Stent Placement In Glaucoma

The XEN Gel Stent is a minimally invasive device designed to lower IOP in open-angle glaucoma by creating a controlled drainage pathway. Measuring approximately 6 mm and composed of a soft, gelatin-derived material, it is engineered for biocompatibility and flexibility to reduce scarring and resistance. Unlike traditional filtration surgeries, it is inserted using an ab interno approach, avoiding extensive conjunctival dissection. This technique minimizes surgical trauma and shortens recovery time, making it a viable option for patients needing IOP reduction without invasive surgery.

The procedure begins with a small corneal incision to introduce the preloaded injector containing the XEN Gel Stent. Under gonioscopic guidance, the device is advanced through the trabecular meshwork and sclera, positioning one end in the anterior chamber and the other in the subconjunctival space. This placement allows aqueous humor to bypass the compromised outflow pathways and drain into the subconjunctival reservoir for absorption. The stent’s 45-micron lumen diameter provides sufficient resistance to prevent overfiltration while maintaining steady IOP reduction.

A key advantage of the XEN Gel Stent is its ability to establish a low-resistance outflow pathway with minimal tissue disruption. This controlled drainage mechanism helps prevent hypotony, which can lead to complications such as choroidal effusion or maculopathy. Clinical studies show an average IOP reduction of 25-40% from baseline, with many patients maintaining stable pressure for years. However, outcomes vary based on preoperative IOP, prior treatments, and individual healing responses.

Trabeculectomy Steps In Glaucoma

Trabeculectomy is a well-established surgical procedure for lowering IOP, particularly when other treatments fail. Unlike minimally invasive techniques, it involves creating a new drainage pathway by surgically bypassing the trabecular meshwork and scleral resistance. The procedure, performed under local or general anesthesia, requires precise tissue handling to ensure long-term success.

The surgery begins with a conjunctival peritomy, where the conjunctiva and Tenon’s capsule are dissected from the sclera, typically in the superior quadrant. A partial-thickness scleral flap is then fashioned to act as a controlled valve for aqueous outflow. The size and thickness of this flap influence fluid egress and help prevent complications like hypotony. Beneath this flap, a sclerostomy is created to establish direct communication between the anterior chamber and subconjunctival space.

To maintain outflow, a peripheral iridectomy is performed to prevent pupillary block, which could elevate IOP postoperatively. The scleral flap is then repositioned and secured with sutures, adjusted to balance drainage while preventing excessive flow. Proper tension is crucial—tight sutures may lead to inadequate pressure reduction, while loose sutures can cause overfiltration and associated complications.

Finally, the conjunctiva is meticulously closed to prevent leakage, ensuring the integrity of the filtering bleb. A watertight seal is essential for proper aqueous humor collection and absorption. Sutures, either absorbable or non-absorbable, are used based on patient-specific factors like tissue elasticity and healing potential. Proper wound closure also reduces the risk of infection, a significant concern in filtration surgeries.

Filtration And Fluid Regulation In Postoperative Eyes

Effective filtration and fluid regulation after glaucoma surgery are critical for long-term IOP stability. Success depends on controlled aqueous humor movement from the anterior chamber into the subconjunctival space, where it is absorbed. Surgeons aim to balance sufficient outflow with preventing excessive filtration that could lead to hypotony, which may cause complications like choroidal effusion or maculopathy.

The filtering bleb’s morphology is a key indicator of fluid regulation. A well-functioning bleb appears diffuse and low-elevated, signifying steady absorption without excessive resistance. Encapsulated or fibrotic blebs increase outflow resistance, raising IOP and risking surgical failure. Conversely, thin-walled, cystic blebs can cause overdrainage and hypotony-related complications. Ophthalmologists monitor bleb characteristics using slit-lamp biomicroscopy and anterior segment optical coherence tomography (OCT) to assess fluid dynamics and intervene when needed.

Pharmacologic modulation of wound healing plays a crucial role in postoperative fluid regulation. Anti-fibrotic agents such as mitomycin-C (MMC) and 5-fluorouracil (5-FU) help suppress excessive scar formation that could obstruct outflow. These agents are carefully dosed to prevent over-inhibition of healing, which could lead to bleb leaks or chronic hypotony. If filtration is insufficient, interventions like bleb needling or suture lysis can restore flow. Postoperative management includes corticosteroids and hypotensive medications tailored to each patient’s response, ensuring controlled IOP while the drainage system stabilizes.

Tissue Responses In Gel Stent Procedures

Tissue response following XEN Gel Stent implantation is influenced by the device’s biocompatibility, surgical precision, and individual healing characteristics. Upon insertion, the stent establishes an aqueous humor outflow pathway, triggering localized remodeling in the subconjunctival space. The gelatin-derived material integrates with surrounding tissues while minimizing inflammation, though fibroblast activity can still impact long-term function. Mild conjunctival edema and low-grade inflammation are common early postoperative findings, usually resolving within weeks as tissues adapt.

Scar formation affects the procedure’s durability. Although the XEN Gel Stent resists excessive fibrosis, some patients develop encapsulation around the subconjunctival reservoir, restricting fluid egress and elevating IOP. This response is more common in individuals with aggressive wound healing or prior ocular surgeries. Surgeons often use mitomycin-C (MMC) during implantation to modulate fibroblast activity and maintain outflow. When scarring occurs, needling procedures can break fibrotic adhesions and restore function.

Tissue Responses In Trabeculectomy

Tissue response following trabeculectomy is shaped by the body’s healing mechanisms, which can either support or compromise long-term success. Unlike minimally invasive procedures that use pre-formed drainage devices, trabeculectomy relies on controlled scarring to maintain aqueous humor outflow. In the early postoperative period, conjunctival and scleral tissues undergo an inflammatory phase, during which fibroblasts migrate to the surgical site and produce extracellular matrix components. While necessary for healing, excessive fibrosis can obstruct the filtration pathway.

Modulating this response is critical in postoperative management. Anti-fibrotic agents such as mitomycin-C (MMC) and 5-fluorouracil (5-FU) are commonly applied intraoperatively or postoperatively to suppress fibroblast proliferation and reduce bleb failure risk. Despite these interventions, some patients develop encapsulated blebs with dense fibrosis, leading to inadequate filtration and rising IOP. Conversely, insufficient scarring can result in overfiltration and hypotony-related complications. Close postoperative monitoring is essential, with interventions like suture adjustment, bleb needling, or revision surgery used as needed to maintain optimal fluid dynamics.