iStent and iStent Inject: The Most Widely Used MIGS Device
What the iStent Is and How It Works
The iStent is a tiny implantable device designed to lower eye pressure in patients with mild-to-moderate open-angle glaucoma. As the most widely used minimally invasive glaucoma surgery (MIGS) device in the world, it offers a gentler alternative to traditional glaucoma surgery with a well-established safety record supported by years of clinical data. At Greenwich Ophthalmology Associates, our glaucoma specialists use the latest generation of iStent technology to help patients manage their glaucoma while reducing their reliance on daily eye drops. If you have been diagnosed with open-angle glaucoma and are exploring your surgical options, understanding how the iStent works can help you make a confident, informed decision about your care.
The iStent is one of the smallest medical devices ever implanted in the human body, yet it plays a meaningful role in managing eye pressure for patients with glaucoma.
In a healthy eye, a fluid called aqueous humor flows through the trabecular meshwork, a sponge-like drainage tissue located where the iris meets the cornea. In open-angle glaucoma, this meshwork becomes less efficient over time, causing fluid to build up and intraocular pressure (IOP) to rise. The iStent is a microscopic titanium stent that is placed directly into the trabecular meshwork, creating a permanent opening that bypasses the area of greatest resistance. This restored pathway allows aqueous humor to drain more freely into Schlemm's canal, the eye's natural drainage channel, helping to lower IOP.
By creating a direct connection between the front chamber of the eye and Schlemm's canal, the iStent restores a more natural outflow of fluid. Studies with up to seven years of follow-up data show that the iStent can achieve sustained IOP reductions, with many patients reaching a mean postoperative pressure of approximately 15 mmHg. This pressure reduction can help slow the progression of optic nerve damage that leads to permanent vision loss in glaucoma.
Glaukos, the manufacturer of the iStent, has developed several generations of this technology. The product line includes the original iStent, the second-generation iStent inject, the refined iStent inject W, and the iStent infinite. Each successive version has built upon the safety and efficacy of earlier models while introducing design improvements that benefit both the surgeon and the patient. Our glaucoma specialists select the version best suited to each patient's specific clinical situation.
Differences Between the iStent and iStent Inject
While all iStent devices share the same core goal of improving trabecular outflow, meaningful differences exist between generations that affect performance and how they are implanted.
The first-generation iStent received FDA approval in 2012 as the first MIGS device cleared for use in the United States. It consists of a single L-shaped titanium micro-stent that is inserted through a small incision during surgery. The original device demonstrated that a tiny implant placed in the trabecular meshwork could safely and effectively reduce IOP when combined with cataract surgery.
The iStent inject, approved in 2018, represented a significant step forward. Rather than one stent, the iStent inject delivers two micro-stents through a single pre-loaded injector, allowing the surgeon to access two different areas of Schlemm's canal and improve fluid outflow across a wider portion of the drainage system. Clinical comparisons have shown that iStent inject eyes tend to achieve lower IOP at six months and a higher proportion of patients reaching target pressures compared to the original single-stent design. The iStent inject W, approved in 2020, refined the design further with a wider flange that improves stent retention and procedural predictability.
In current clinical practice, the iStent inject W is the standard version implanted during cataract surgery for patients with mild-to-moderate open-angle glaucoma. Additionally, the iStent infinite, which contains three stents and was approved in 2022, allows implantation as a standalone procedure in patients whose glaucoma is not adequately controlled by medications or prior surgeries. When you visit for a consultation, we will explain which device aligns with your diagnosis and treatment goals. You can also learn how the iStent compares to other options by reading about the differences between MIGS procedures.
Who Is a Good Candidate for iStent Implantation
Not every patient with glaucoma is a candidate for the iStent, and a thorough evaluation is the first step in determining whether this approach is right for you.
The iStent is FDA-approved for adult patients who have mild-to-moderate primary open-angle glaucoma and are already undergoing cataract surgery. Good candidates typically include patients who are currently using one or more glaucoma eye drops and would benefit from reducing that medication burden. Patients who have difficulty remembering their drops, experience side effects from glaucoma medications, or want a proactive approach to managing their pressure alongside cataract removal are often well suited to this procedure.
Patients with advanced or aggressive glaucoma may need a procedure that provides a greater degree of IOP reduction, such as the XEN Gel Stent or traditional filtration surgery. The iStent is also not typically recommended for angle-closure glaucoma or secondary forms of glaucoma where the trabecular meshwork is not the primary site of outflow resistance. During your evaluation, our glaucoma specialists will measure your eye pressure, examine your drainage angle, assess your optic nerve health, and review your medication history to determine whether iStent implantation or a different approach will give you the best outcome.
Combining iStent with Cataract Surgery
One of the greatest advantages of the iStent is that it can be implanted at the same time as cataract surgery, addressing two conditions in a single visit to the operating room.
Both cataract surgery and iStent implantation are performed through the same small corneal incision, so adding the iStent does not require additional cuts or significantly extend the procedure. The cataract is removed and a new intraocular lens is placed first, and then the iStent is gently inserted into the trabecular meshwork while the surgeon has a clear view of the drainage angle. This combined approach means patients can improve their vision from cataract removal while simultaneously gaining better control of their glaucoma. You can learn more about how these two procedures complement each other on our page about glaucoma and cataract surgery performed together.
The combined procedure is performed on an outpatient basis using topical or local anesthesia, meaning you will be awake but comfortable throughout. The entire surgery, including both the cataract removal and the iStent placement, generally takes around 15 to 20 minutes. You will not feel the stent being placed, and most patients describe the experience as quick and painless. After the procedure, you will rest briefly in a recovery area before going home the same day.
Recovery from combined cataract and iStent surgery is similar to recovering from cataract surgery alone. Most patients notice improved vision within a few days, and any mild discomfort typically resolves quickly with prescribed eye drops. You will have several follow-up appointments in the weeks after surgery so our team can monitor your eye pressure, check the position of the stent, and determine whether your glaucoma medications can be reduced or discontinued. Most patients return to their normal daily activities within a week.
Frequently Asked Questions
Clinical studies have shown that the iStent, when combined with cataract surgery, achieves a meaningful and sustained reduction in IOP. Seven-year follow-up data demonstrate that patients can maintain a mean IOP of approximately 15 mmHg, and a high proportion of patients achieve the target pressure of 18 mmHg or below. Success rates vary depending on baseline pressure and the severity of glaucoma, which is why a personalized assessment is essential before surgery.
Many patients are able to reduce or eliminate their glaucoma eye drops after iStent implantation. In comparative studies, the iStent inject has been associated with medication reductions of over 90% from baseline at 12 months, and a significant proportion of patients become medication-free. Your individual outcome will depend on your starting medication load and the stability of your eye pressure after surgery.
The iStent has a favorable safety profile, which is one of the reasons it has become the most widely implanted MIGS device. Potential risks include temporary increases in eye pressure, mild inflammation, stent obstruction, or the rare need for repositioning. Serious complications are uncommon, and the overall risk profile is lower than that of more invasive glaucoma surgeries such as trabeculectomy or tube shunt procedures.
When performed alongside cataract surgery, the iStent adds only a few minutes to the total operating time. The stent placement itself typically takes less than five minutes. The combined procedure from start to finish usually lasts around 15 to 20 minutes, and you can expect to be at the surgical center for approximately two to three hours total, including preparation and recovery time.
Yes, the iStent is FDA-approved and covered by Medicare and most private insurance plans when implanted during cataract surgery. Because it is placed as part of an already scheduled cataract procedure, the additional cost to the patient is often minimal. Coverage for standalone procedures, such as those using the iStent infinite, may vary, and our team can help verify your specific benefits before surgery.
Because the iStent works within the eye's natural drainage anatomy and does not alter surrounding tissue, it preserves your options for future glaucoma treatment. If additional pressure lowering is needed, our glaucoma specialists can recommend further interventions, including other MIGS devices like the Hydrus Microstent, laser treatments, or more traditional glaucoma surgery. The iStent does not limit or complicate any of these subsequent approaches.
Start a Conversation About iStent With Our Glaucoma Team
If you are managing open-angle glaucoma with eye drops and considering cataract surgery, the iStent may offer a meaningful opportunity to simplify your treatment while protecting your vision for the long term. Our fellowship-trained glaucoma specialists at Greenwich Ophthalmology Associates in the greater NY/CT region are experienced in the full range of MIGS technologies and can help you understand whether iStent implantation is the right next step. We welcome you to schedule a consultation to discuss your diagnosis, review your options, and build a treatment plan tailored to your needs.
We encourage you to bring your questions and concerns to your next appointment so we can develop a care plan that addresses your goals and lifestyle.
Learn More About Related Topics
To further your understanding, explore our resources on Comparing MIGS Procedures: iStent vs. Hydrus vs. XEN, MIGS and Traditional Glaucoma Surgery, and Minimally Invasive Glaucoma Surgery (MIGS) Guide.
You may also find these pages helpful: Open-Angle Glaucoma: The Most Common Form Explained, Angle-Closure Glaucoma: Recognizing the Emergency, and Angle-Closure Glaucoma: Symptoms & Emergency Treatment.
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