Long-term Safety and Efficacy of a Modified Suprachoroidal Silicone Tube (SST) Shunt

This observational study serves as an extension to a prior retrospective cross-sectional trial that initially investigated the clinical outcomes of suprachoroidal silicone tube (SST) shunt implantation in patients diagnosed with primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PXG). In the initial study, participants underwent the SST shunt procedure and were followed for an average period of 19 months post-surgery. This initial study focused on assessing intraocular pressure (IOP) reduction and the initial safety profile of the SST device. However, as the device's long-term impact on ocular health, particularly the corneal endothelium, was not fully understood, this follow-up observational study was designed and implemented approximately 1 year after the last FU data collection was completed.

The SST shunt device is a relatively novel intervention positioned between minimally invasive glaucoma surgeries (MIGS) and traditional tube shunt surgeries. By facilitating aqueous humor drainage from the anterior chamber to the suprachoroidal space, the SST shunt provides a unique pathway for IOP reduction. Given the risks associated with corneal endothelial health in glaucoma patients, especially following invasive procedures, understanding the long-term impact of the SST shunt on endothelial cell counts (ECC) is essential.

Study Objectives:

The primary objective of this observational study is to evaluate the long-term safety and efficacy of the SST shunt in reducing IOP and preserving endothelial cell health. This involves:

Tracking changes in ECC attributable solely to the SST shunt, as the study design excluded additional interventions to isolate the device's effect.

Assessing the device's ability to maintain effective IOP control over an extended period.

Documenting any adverse events, including device migration, extrusion, and other complications, to understand the SST shunt's overall impact on ocular health.

Study Population:

The study is going to re-evaluate approximately 66 eyes, who had previously undergone SST shunt implantation, either as a standalone procedure or in combination with cataract surgery. These evaluations are going to be conducted within the period between 8 Nov/2024 and 30 Nov/2024.Participants in this observational study met the original inclusion criteria set forth in the retrospective trial. This included a cohort of Caucasian patients aged 41 to 88 years (mean age: 69), with a gender distribution of 40 men and 26 women. All patients were untreated with glaucoma surgeries or laser therapies prior to the SST implantation, providing a clean baseline for evaluating the SST device's isolated effects.

Study Design:

This study is observational and non-interventional, meaning it involved no additional treatments or manipulations beyond the baseline SST shunt implantation. This approach allowed for a naturalistic assessment of ECC and other clinical parameters over time. By not introducing any new variables, the study design aimed to observe and measure outcomes that could be directly attributed to the SST shunt. This design offers valuable insights into the natural progression of endothelial cell health and IOP management in patients who have undergone SST implantation without the influence of confounding factors.

Clinical Assessments and Follow-Up Procedures With an average 31 months (std. dev: 8 monts) follow-up, participants underwent assessments to monitor IOP, visual acuity, ECC, C/D ratio and any shunt-related adverse events.

Outcome Measures:

Primary Outcomes:

Endothelial Cell Loss: Tracked to assess corneal integrity. IOP Control: Success was defined as ≥20% reduction in IOP, with "complete success" for IOP control without medications, "qualified success" with medications, and "failure" for <20% IOP reduction or IOP >21 mmHg.

Secondary Outcomes:

Hypotony: Defined as IOP <5 mmHg, categorized as transient or permanent. Device Migration/Extrusion: Monitored to assess mechanical stability. Other Adverse Events: Any device-related complications documented for safety analysis.