Comparing MIGS Procedures: iStent vs. Hydrus vs. XEN
Key Differences Between MIGS Devices
Minimally invasive glaucoma surgery, commonly known as MIGS, has transformed how eye doctors treat glaucoma by offering safer alternatives to traditional surgical approaches. If you have been diagnosed with glaucoma and your current treatment plan needs adjustment, understanding the differences between the most widely used MIGS devices can help you feel confident about your next steps. At Greenwich Ophthalmology Associates, our fellowship-trained glaucoma specialists help patients throughout the greater NY/CT region choose the MIGS approach best suited to their individual condition. This guide compares three leading MIGS devices, the iStent, Hydrus Microstent, and XEN Gel Stent, so you can have a more informed conversation with your doctor about which option may be right for you.
Each MIGS device works through a different mechanism to lower intraocular pressure (IOP), the primary risk factor for glaucoma progression. The fundamental distinction between these three devices comes down to where they redirect fluid within the eye. The iStent and Hydrus both target Schlemm's canal, a natural drainage channel inside the eye, while the XEN creates a completely different drainage route beneath the surface of the eye. Understanding how these devices differ in design, placement, and drainage pathway is essential for evaluating your options.
The iStent and iStent inject are the most widely implanted MIGS devices in the world. These tiny titanium stents are placed directly into Schlemm's canal to bypass the trabecular meshwork, which is the tissue that becomes clogged in open-angle glaucoma. The original iStent uses a single bypass, while the newer iStent inject W places two micro-stents to access multiple collector channels simultaneously. By restoring natural aqueous outflow through the conventional drainage pathway, these devices lower IOP with a very favorable safety profile. The iStent was the first MIGS device to receive FDA approval in 2012, giving it the longest track record of any device in this category.
The Hydrus Microstent also targets Schlemm's canal but takes a different approach. Rather than creating a single point of bypass, the Hydrus is an 8-millimeter scaffold that spans roughly 90 degrees of Schlemm's canal. This opens a larger section of the canal and accesses more downstream collector channels at once. Laboratory studies have shown that the Hydrus increases outflow facility by a greater margin compared to dual iStent placement, which may explain the slightly greater pressure reduction some studies have observed. The Hydrus was evaluated in the HORIZON trial, the largest randomized controlled MIGS trial to date.
The XEN Gel Stent uses an entirely different drainage pathway compared to the iStent and Hydrus. Instead of routing fluid through Schlemm's canal, the XEN creates a subconjunctival drainage route, channeling aqueous humor from the anterior chamber to a space beneath the conjunctiva on the surface of the eye. This mechanism is more similar to trabeculectomy than to other MIGS devices, which is why the XEN can achieve more substantial pressure reductions. The XEN is a soft, flexible gelatin tube that is typically 6 millimeters long, and it is designed for patients with moderate-to-advanced glaucoma who need greater IOP lowering than canal-based devices can typically provide.
The iStent and iStent inject create a trabecular meshwork bypass into Schlemm's canal, using the eye's conventional outflow system. The Hydrus Microstent acts as a scaffold within Schlemm's canal to open a wider segment of that same conventional outflow pathway. The XEN Gel Stent works through subconjunctival filtration, a non-conventional outflow route that is similar in concept to a trabeculectomy. This difference in drainage pathway is the single most important factor that influences how much pressure each device can lower, what the recovery looks like, and which patients are best suited for each option.
Comparing Pressure Reduction, Recovery, and Long-Term Results
The degree of IOP reduction varies across devices and depends on factors such as baseline eye pressure, glaucoma severity, and whether the MIGS procedure is combined with cataract surgery. Research consistently shows that combining MIGS with cataract surgery yields greater IOP reduction than MIGS alone, with an additional 2 to 2.8 mmHg of pressure lowering compared to cataract surgery by itself. The iStent and Hydrus are FDA-approved specifically for use in combination with cataract surgery, while the XEN can be implanted either as a standalone procedure or at the time of cataract extraction.
One of the most appealing features of MIGS is a faster, more comfortable recovery compared to traditional glaucoma surgeries. However, the recovery timeline and long-term follow-up requirements differ depending on which device is used, and understanding these differences can help you plan accordingly. All three devices have published clinical trial data demonstrating sustained IOP lowering over multiple years, though results tend to drift slightly upward over time with any MIGS procedure.
Clinical studies have shown that both the iStent inject and the Hydrus Microstent, when combined with cataract surgery, reduce IOP by approximately 15 to 30 percent from baseline in patients with mild-to-moderate open-angle glaucoma. A network meta-analysis of randomized controlled trials found that the Hydrus may offer a slight advantage in IOP lowering compared to a single iStent, although the difference narrows when two iStents are implanted. Long-term comparative data at 48 months show no significant difference in surgical success rates between Hydrus and iStent inject in matched patient populations. A significant percentage of patients remain medication-free at several years post-implantation with either device.
Because the XEN creates a subconjunctival bleb, or fluid pocket, it can achieve more aggressive pressure reductions, often in the range of 30 to 50 percent. This makes the XEN better suited for patients with moderate-to-advanced glaucoma or those who need to reach lower target pressures. However, the greater efficacy comes with a higher likelihood of needing a follow-up procedure called needling if the bleb scars down over time. Published data extending to five years show strong pressure-lowering efficacy, though studies also reveal that 30 to 40 percent of XEN patients may need at least one needling within the first two years.
Both canal-based devices are implanted through the same tiny incision used during cataract surgery, so recovery closely mirrors that of a standard cataract procedure. Most patients notice improved comfort within a few days and return to normal activities within one to two weeks. Post-operative drops typically include an antibiotic and anti-inflammatory, used for roughly four weeks. Because these devices work within the eye's natural drainage system, there is no external bleb to monitor, which simplifies aftercare. Patients who receive an iStent or Hydrus during cataract surgery often resume driving within a few days.
Recovery from XEN implantation tends to require a longer follow-up schedule because the procedure creates a subconjunctival bleb that must be carefully managed. Anti-metabolite medications, such as mitomycin C, are applied at the time of surgery to reduce scarring around the bleb. Patients may need more frequent visits during the first few months, and a small percentage will require a needling procedure in the office to maintain bleb function. Vision may fluctuate more in the early weeks compared to canal-based MIGS, though most patients stabilize within one to three months. Patients may be advised to limit strenuous activity for a slightly longer window while the bleb matures.
Choosing the Right MIGS Procedure
Choosing the right MIGS procedure is a decision best made with a specialist who understands both the clinical evidence and your individual needs. The recommendation depends on several factors, including your glaucoma severity, current IOP, number of medications you are taking, whether you have a coexisting cataract, and your target pressure. Anatomy of the drainage angle, prior surgical history, and your ability to attend frequent follow-up visits also play a role in determining which device is the best fit.
At Greenwich Ophthalmology Associates, our board-certified, fellowship-trained glaucoma specialists use advanced diagnostic technology to evaluate your glaucoma stage, drainage angle anatomy, and overall eye health before recommending a personalized treatment plan. Below are answers to the questions patients most commonly ask when weighing their MIGS options.
One advantage of MIGS is that these procedures preserve the anatomy of the eye, leaving future surgical options open. A patient who does not achieve adequate pressure control with a canal-based device can undergo additional MIGS, laser treatment, or traditional glaucoma surgery if needed. The XEN can also be revised through needling or replaced, and other filtering procedures remain available. This tissue-sparing quality is one of the key reasons MIGS has become a preferred early intervention for many glaucoma specialists.
The XEN Gel Stent is FDA-approved as a standalone procedure and does not require cataract surgery. The iStent inject W received a standalone indication as well, expanding its use to patients who do not yet need cataract removal. The Hydrus Microstent is currently approved for use in combination with cataract surgery. Your glaucoma specialist can determine which standalone or combined approach fits your clinical needs based on your specific diagnosis and surgical history.
All three devices have favorable safety profiles compared to traditional glaucoma surgery. The most common complications with canal-based devices include transient blood reflux in the eye (hyphema), which typically resolves within days, and peripheral anterior synechiae, a mild adhesion of the iris. Complication rates for the iStent and Hydrus are generally reported at around 20 to 36 percent for minor events, with serious complications being rare. The XEN carries additional risks related to bleb management, including hypotony (excessively low eye pressure), bleb leaks, and the need for needling in up to one-third of patients.
Traditional procedures such as trabeculectomy and tube shunt surgery typically achieve greater IOP reductions than canal-based MIGS, making them more appropriate for advanced glaucoma. However, traditional surgeries carry higher complication rates and longer recovery periods. MIGS fills an important gap for patients with mild-to-moderate disease who need more pressure reduction than medications or laser alone can provide but do not yet require the intensity of a trabeculectomy. The XEN Gel Stent bridges these two categories, offering more filtration than a canal-based device with less invasiveness than a full trabeculectomy.
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