How iStents and Other MIGS Procedures Help Control Glaucoma Over Time
Glaucoma is a long-term condition that damages the optic nerve, usually because of increased pressure inside the eye. The goal of treatment is simple in principle: reduce intraocular pressure (IOP) to slow or prevent further damage to vision.
Traditionally, glaucoma treatment has relied on eye drops, laser procedures, or more invasive surgeries such as trabeculectomy. Over the past decade, however, a newer group of procedures has become available known as Minimally Invasive Glaucoma Surgery (MIGS).
One of the most widely used MIGS devices is the iStent.
MIGS procedures are designed to lower eye pressure with less surgical trauma and fewer risks than traditional glaucoma surgery. While they may not reduce pressure as dramatically as larger operations, they can play an important role in managing glaucoma over time, particularly in patients with mild to moderate disease.
Understanding how these procedures work helps explain what patients can realistically expect from them.
What Is MIGS?
MIGS refers to a group of surgical techniques that aim to improve fluid drainage from the eye using very small implants or microscopic surgical openings.
These procedures share several characteristics:
• They are performed through tiny incisions
• They usually involve minimal disruption to eye tissues
• Recovery tends to be relatively quick
• The risk profile is generally lower than traditional glaucoma surgery
Most MIGS procedures target the eye’s natural drainage system, which is located in the trabecular meshwork and Schlemm’s canal.
The iStent works by improving flow through this pathway.
How Eye Pressure Builds Up in Glaucoma
Inside the eye, a clear fluid called aqueous humour is continuously produced. This fluid nourishes the eye and maintains its shape.
Normally, it drains out through a microscopic filtration system at the front of the eye called the trabecular meshwork.
In many forms of glaucoma, this drainage system becomes less efficient. Fluid leaves the eye more slowly, which causes pressure to rise.
Over time, elevated pressure can damage the optic nerve, leading to gradual and often irreversible loss of peripheral vision.
Most glaucoma treatments aim to either reduce fluid production or improve drainage.
MIGS procedures focus primarily on improving drainage.
How the iStent Works
The iStent is a very small titanium implant designed to bypass the trabecular meshwork.
It is one of the smallest medical implants used in the body.
During the procedure, the surgeon inserts the stent into Schlemm’s canal, which is part of the eye’s natural drainage system. The stent creates a tiny channel that allows aqueous fluid to flow more easily out of the eye.
In simple terms, it acts like a microscopic drainage pipe, helping fluid bypass the area of greatest resistance.
The procedure is usually performed through the same small incision used for cataract surgery, which is why it is often done at the same time as cataract removal.
Why iStents Are Often Combined With Cataract Surgery
Many patients with glaucoma also develop cataracts as they age.
Combining MIGS with cataract surgery offers several advantages:
• No additional external incisions are needed
• The surgery adds only a small amount of additional time
• Cataract surgery itself can slightly reduce eye pressure
The combined effect may provide a modest but useful reduction in pressure, which can help reduce reliance on eye drops.
However, MIGS can also be performed as a standalone procedure in selected patients.
How Much Pressure Reduction Can Be Expected?
One important point about MIGS is that they usually provide moderate pressure reduction rather than dramatic drops in pressure.
Studies of iStents generally show:
• A reduction in intraocular pressure of several millimetres of mercury
• A decrease in the number of glaucoma medications required
For many patients, the goal is not necessarily to eliminate drops completely, but rather to reduce the treatment burden while maintaining good pressure control.
Some patients are able to stop one or more medications after surgery, while others continue using drops but at a lower intensity.
How MIGS Helps Control Glaucoma Over Time
Glaucoma is a lifelong condition, and treatment strategies often evolve over many years.
MIGS procedures can contribute to long-term management in several ways.
Lowering Baseline Pressure
Even a modest reduction in eye pressure can slow glaucoma progression.
For many patients, bringing pressure down a few points can help maintain stability over time.
Reducing Medication Dependence
Glaucoma eye drops are effective but can be difficult to maintain over decades.
Common challenges include:
• Forgetting doses
• Side effects such as redness or irritation
• Long-term effects on the ocular surface
If MIGS reduces the need for multiple medications, it can improve comfort and adherence to treatment.
Providing Earlier Surgical Intervention
Historically, glaucoma surgery was reserved for more advanced disease because of the risks involved.
MIGS has changed this approach slightly by providing a lower-risk surgical option earlier in the disease course.
This allows some patients to address pressure control before glaucoma becomes more advanced.
Preserving Future Treatment Options
Another advantage of MIGS is that it usually does not prevent future glaucoma procedures.
If additional pressure reduction is needed later, patients can still undergo:
• Laser treatments
• Further MIGS procedures
• Traditional surgeries such as trabeculectomy or tube implants
Because MIGS procedures cause relatively little tissue disruption, they tend to leave these options open.
Not Every Patient Is Suitable
While MIGS can be helpful, they are not appropriate for every type of glaucoma.
They are generally most effective in:
• Mild to moderate open-angle glaucoma
• Patients undergoing cataract surgery
• Individuals who need modest pressure reduction
They may be less effective in:
• Advanced glaucoma requiring very low target pressures
• Certain secondary glaucomas
• Eyes with significant scarring of the drainage system
In these situations, more traditional glaucoma surgeries may still be necessary.
Why Multiple Stents Are Sometimes Used
Some newer versions of the iStent involve implanting two or more stents.
The reason is that the eye’s drainage system is not uniform. Some sections of Schlemm’s canal drain better than others.
By placing more than one stent, surgeons may increase the likelihood of connecting with functioning collector channels.
This can potentially improve pressure reduction, although the overall effect still tends to be moderate.
Safety Considerations
One reason MIGS procedures have become popular is their favourable safety profile compared with traditional glaucoma surgery.
Serious complications are uncommon.
Possible issues include:
• Small amounts of bleeding inside the eye
• Temporary pressure fluctuations
• Rare blockage or malposition of the stent
In most cases, recovery is relatively straightforward and vision returns quickly, especially when combined with cataract surgery.
However, as with any surgical procedure, outcomes can vary between individuals.
The Big Picture
MIGS procedures such as the iStent represent an important addition to glaucoma treatment.
They do not replace medications or traditional surgery entirely, but they offer another option in the spectrum of care.
For many patients with mild to moderate glaucoma, they can:
• Lower eye pressure modestly
• Reduce reliance on multiple medications
• Be performed safely alongside cataract surgery
Over time, this may help maintain better pressure control with fewer treatment burdens.
A Long-Term Approach to Glaucoma
Glaucoma management is rarely about a single treatment solving the problem permanently. Instead, it usually involves a series of strategies over many years.
MIGS procedures fit into this long-term approach by offering a relatively gentle way to improve fluid drainage and support pressure control.
While they may not eliminate the need for ongoing monitoring or additional treatments, they can play a valuable role in helping patients maintain stable vision over time.