iStent Glaucoma

Key Features of the iStent:

1. Size: The iStent is extremely small, roughly the size of a grain of sand (~1 mm in length). Despite its tiny size, it is effective in facilitating fluid outflow from the eye.

2. Material: It is made from surgical-grade titanium, which is biocompatible and designed to last inside the eye without causing inflammation or rejection.

3. Mechanism: The iStent is designed to bypass the natural blockage of the trabecular meshwork and facilitate the drainage of fluid directly into Schlemm’s canal, the natural drainage channel in the eye.

How the iStent Works:

In patients with open-angle glaucoma, the trabecular meshwork becomes less efficient at draining aqueous humor, leading to increased intraocular pressure. The iStent is placed directly into the trabecular meshwork, creating a direct pathway for fluid to drain into Schlemm’s canal, which can then reabsorb the fluid. This helps reduce IOP and slow down the progression of glaucoma.

iStent Procedure:

The implantation of the iStent is typically performed during cataract surgery but can be done as a standalone procedure as well. Here's an overview of how it works:

1. Access: A small incision is made in the cornea to access the anterior chamber of the eye.

2. Placement: Using a specialized injector, the surgeon places the iStent into the trabecular meshwork, where it provides a bypass for fluid to flow into Schlemm’s canal.

3. Multiple Devices: In some cases, more than one iStent may be implanted to further improve fluid drainage and reduce eye pressure.

Types of iStents:

Over the years, different versions of the iStent have been developed to enhance their effectiveness:

1. iStent (First Generation): This was the original version of the device, typically implanted as a single stent.

2. iStent inject (Second Generation): The iStent inject includes two smaller stents that are implanted into the trabecular meshwork. These two stents help provide better outflow by targeting multiple areas of Schlemm’s canal.

3. iStent inject W: This version has an enhanced design and comes with a wider lumen (the opening of the stent), improving fluid flow.

Benefits of iStent:

• Minimally Invasive: The iStent is inserted through a small incision, and the procedure is less invasive than traditional glaucoma surgeries like trabeculectomy or tube shunts.

• Quick Recovery: Patients typically experience a faster recovery time, with less trauma to the eye and fewer complications compared to more aggressive glaucoma surgeries.

• Reduction in Medications: Many patients who receive an iStent are able to reduce their dependence on glaucoma medications, which can have side effects or become ineffective over time.

• Can Be Combined with Cataract Surgery: This is especially convenient for older patients who are more likely to have both cataracts and glaucoma.

• Effective IOP Reduction: The iStent provides sustained IOP reduction, which helps slow down the progression of glaucoma and protect the optic nerve.

Candidates for iStent:

• Primary Open-Angle Glaucoma (POAG): The iStent is FDA-approved for use in patients with mild to moderate POAG.

• Combined with Cataract Surgery: It is often used in patients undergoing cataract surgery who also have glaucoma, providing a dual benefit of treating both conditions at once.

• Mild to Moderate Glaucoma: The iStent is typically used in cases where glaucoma is not advanced enough to require more invasive surgeries like trabeculectomy.

Risks and Complications:

While the iStent is considered safe and effective, there are some risks associated with the procedure, including:

• Hyphema (bleeding in the anterior chamber)

• Transient Elevation in IOP: Some patients may experience a temporary spike in IOP following surgery.

• Stent Misplacement: Rarely, the stent may be placed incorrectly or become dislodged, potentially requiring revision surgery.

• Insufficient Pressure Reduction: In some cases, the iStent may not lower IOP as much as expected, and additional treatment may be needed.

Postoperative Care:

After surgery, patients are usually prescribed anti-inflammatory and IOP-lowering medications to aid healing and ensure the device functions properly. Regular follow-up visits are essential to monitor IOP and check the positioning and effectiveness of the stent.

Alternatives to iStent:

Other MIGS devices are available for glaucoma treatment, including:

• Hydrus Microstent: Similar to the iStent, the Hydrus stent also targets the trabecular meshwork and Schlemm’s canal to enhance fluid drainage.

• XEN Gel Stent: This device is implanted into the subconjunctival space, creating a new drainage pathway for fluid to exit the eye.

Conclusion:

The iStent is a highly effective, minimally invasive option for lowering intraocular pressure in patients with mild to moderate open-angle glaucoma. It offers the advantages of quick recovery, reduced reliance on medications, and the ability to combine the procedure with cataract surgery. For patients with more advanced glaucoma, other treatments or more aggressive surgeries may be needed, but the iStent remains a valuable tool in glaucoma management, particularly for early-stage cases.