Question

Write briefly about the mechanism of action of these devices.

Hint:

MIGS devices work by improving aqueous humor outflow through bypassing or modifying natural drainage pathways, providing an effective and minimally invasive way to reduce IOP.

Answer 1

The mechanism of action of MIGS devices is to improve aqueous humor drainage, thereby reducing intraocular pressure (IOP) without the need for large incisions or significant tissue disruption. The different MIGS devices achieve this goal in various ways, primarily targeting the trabecular meshwork, Schlemm’s canal, or creating alternative drainage pathways. Below is a summary of the mechanisms for some of the most commonly used MIGS devices:
1. iStent (Glaukos):
- The iStent is a small titanium device that is implanted into the trabecular meshwork to create a permanent bypass, allowing aqueous humor to flow directly into Schlemm's canal and then into the eye’s venous system, bypassing the resistance of the trabecular meshwork.
2. iStent Inject (Glaukos):
- The iStent Inject places two microstents into the trabecular meshwork. These stents open up Schlemm's canal and improve fluid drainage, helping to reduce IOP by increasing the outflow of aqueous humor through the natural drainage pathway.
3. Hydrus Microstent (Ivantis):
- The Hydrus Microstent is a flexible scaffold that is inserted into Schlemm's canal to create a larger outflow pathway. It extends the canal and provides a scaffold for better drainage, which reduces IOP by improving aqueous humor flow through the trabecular meshwork.
4. Xen Gel Stent (AbbVie):
- The Xen Gel Stent is inserted into the anterior chamber and provides an artificial outflow pathway for aqueous humor, bypassing the trabecular meshwork entirely. The stent directs the fluid into the subconjunctival space, where it is absorbed into the bloodstream.
5. Kahook Dual Blade (New World Medical):
- The Kahook Dual Blade performs goniotomy, where a small portion of the trabecular meshwork is excised, creating a new pathway for aqueous humor to drain from the anterior chamber to Schlemm’s canal and the outflow system.
6. Trabectome (NeoMedix):
- The Trabectome removes part of the trabecular meshwork through a small incision, allowing aqueous humor to flow more freely into the trabecular outflow system, thereby reducing IOP.
7. Omni Surgical System (Sight Sciences):
- The Omni Surgical System performs goniotomy and trabeculotomy in a single step. It removes part of the trabecular meshwork and clears the Schlemm’s canal, creating a more open channel for aqueous humor to drain out of the eye.
8. CyPass Micro-Stent (Alcon):
- The CyPass Micro-Stent created an outflow pathway for aqueous humor from the anterior chamber to the suprachoroidal space, bypassing the trabecular meshwork and canal entirely, and allowing fluid to be absorbed through the choroidal vasculature.