How Glaucoma Stents Perform in Highly Myopic Eyes
People with severe nearsightedness may face more than blurry distance vision. High myopia is also associated with an increased risk of glaucoma, a disease that damages the optic nerve and can cause permanent vision loss if it progresses.
For patients who have both cataracts and glaucoma, minimally invasive glaucoma surgery (MIGS) may offer an opportunity to address both conditions during the same operation. However, the results of two commonly used glaucoma stents in highly myopic eyes suggest that their pressure-lowering benefits may be more limited than expected.
A multicenter study published in Eye and Vision in 2026 examined the iStent inject and Hydrus microstent over 24 months. The researchers found that both devices helped some patients reduce eye pressure or medication use, but neither reached the proposed minimum clinically important success threshold for MIGS combined with cataract surgery.
What the 24-Month Study Examined
The study, titled Surgical outcomes of trabecular micro-bypass minimally invasive glaucoma surgery devices in eyes with high myopia: a 24-month retrospective multicenter cohort study, was published in Eye and Vision, volume 13, article 40, in 2026. The research team included B. C. H. Ang, N. S. Q. Wong, A. Kochar, and colleagues.
The investigators reviewed 252 eyes from 207 participants treated between January 2019 and December 2023 at three tertiary ophthalmology centers: Mahatma Eye Hospital in Trichy, India; Sydney Eye Surgeons in Australia; and the Singapore National Eye Center.
Of the 252 eyes, 128 received the iStent inject and 124 received the Hydrus microstent. Participants had high myopia, defined by a preoperative refractive spherical equivalent of at least minus 6 dioptres and an axial eye length of 26 millimeters or more, along with ocular hypertension or mild-to-moderate primary open-angle glaucoma.
For the glaucoma diagnosis, eligible eyes had a visual field mean deviation better than minus 12 decibels. Patients with certain other anatomical or inflammatory conditions were excluded, and every participant had at least 12 months of follow-up.
Nearly all eyes underwent phacoemulsification cataract surgery alongside the glaucoma procedure: 96.1% in the iStent group and 100% in the Hydrus group. This is important because the findings primarily describe combined cataract and glaucoma surgery, rather than stent implantation in isolation.
Comparing iStent Inject and Hydrus Results
Both implants are designed to improve the movement of aqueous humor, the fluid circulating inside the eye. By creating a pathway through the trabecular meshwork, they help fluid reach the eye’s natural drainage system and may reduce intraocular pressure (IOP).
At 24 months, a reduction in eye pressure of at least 20% from baseline while continuing glaucoma medication was achieved by 35.8% of Hydrus-treated eyes and 30.0% of iStent-treated eyes.
When success required the same pressure reduction without glaucoma medication, the proportions were lower: 13.4% for Hydrus and 6.67% for iStent. These figures show why outcomes measured with medication cannot be treated as equivalent to medication-free success.
The study also assessed whether patients reached an IOP of 15 mmHg or lower. With medication, this target was achieved by 55.2% of Hydrus eyes and 63.3% of iStent eyes. Without medication, the respective figures were 28.4% and 21.7%.
Medication use declined significantly from baseline in both groups at every measured follow-up point. Participants started at approximately two glaucoma medications per eye, on average, and were using between 0.5 and 0.6 medications per eye at the two-year mark.
Despite differences in some early measurements, the two devices did not differ significantly in their overall success criteria at 24 months. Hydrus tended to perform better for certain pressure-reduction outcomes during the first six months, while some results favored iStent later in follow-up.
Why High Myopia Can Make Glaucoma Surgery Challenging
Highly myopic eyes often have an elongated shape and structural differences around the optic nerve. Changes involving the lamina cribrosa, the supportive tissue through which optic nerve fibers pass, may increase vulnerability to glaucomatous damage.
The drainage anatomy can also complicate surgery. The Hydrus microstent is designed to sit within Schlemm’s canal, a circular drainage channel in the eye, but anatomical differences in highly myopic eyes may affect how well a fixed-curvature device fits.
During iStent implantation, altered eye anatomy and limited surgical visibility may also contribute to positioning difficulties. The research report discusses previously documented concerns such as implant malposition and over-implantation in highly myopic eyes.
Another consideration is the starting eye pressure. The study cohort had a baseline medicated IOP of approximately 15 mmHg, leaving less room for a large percentage reduction than in patients starting with substantially higher pressure.
The researchers also noted that the cohort included patients with more advanced disease than some landmark trials involving non-myopic eyes. Differences in disease severity, surgical protocols, and outcome definitions mean that comparisons with other studies must be interpreted cautiously.
Safety Findings and Study Limitations
Complication rates were generally low over the study period. Significant pressure elevation was the most frequently reported complication at one month, affecting 4.84% of Hydrus eyes and 4.54% of iStent eyes.
Hyphema, or bleeding inside the front portion of the eye, occurred at one month in 0.8% of Hydrus eyes and 4.5% of iStent eyes. Peripheral anterior synechiae, in which tissue adhesions develop in the drainage angle, occurred at similar rates between the groups.
Only three eyes in the iStent group required another pressure-lowering procedure: filtration surgery at one month, deep sclerectomy at 12 months, and selective laser trabeculoplasty at 24 months. No Hydrus-treated eyes required an additional procedure during the reported follow-up.
However, the low number of complications limited the researchers’ ability to determine whether one implant was definitively safer than the other. The study was retrospective, meaning the investigators analyzed existing clinical records rather than assigning treatments in a randomized trial.
Differences in participating centers and surgeons may also have influenced the results. In addition, preoperative pressure measurements were taken without medication washout, which can complicate comparisons with clinical trials that measure pressure after temporarily stopping treatment under controlled conditions.
The authors concluded that trabecular bypass procedures may remain useful options for selected highly myopic patients, especially when the risks of more invasive surgery are a concern. However, their relatively modest pressure-lowering effects highlight the need for further research into treatment approaches tailored to these eyes.
When to See an Eye Doctor About Glaucoma
Glaucoma often develops without noticeable symptoms in its early stages. People with high myopia, a family history of glaucoma, or previously elevated eye pressure should discuss appropriate examination and monitoring with an eye-care professional.
An assessment may include tonometry to measure eye pressure, gonioscopy to inspect the drainage angle, optic nerve examination, and visual field testing. These evaluations help determine whether glaucoma is present and whether it is progressing.
Seek urgent medical attention if you experience sudden vision loss, severe eye pain, or a painful red eye accompanied by blurred vision, headache, or nausea. These symptoms can indicate an eye emergency and should not be attributed to ordinary nearsightedness.
If you have high myopia and are considering cataract surgery, ask your ophthalmologist whether a glaucoma stent is appropriate for your individual condition. Discuss the expected pressure reduction, the possibility of continuing medication, potential complications, and alternative treatments.
The practical next step is to review your current eye pressure, visual field results, and optic nerve health with your specialist. The two-year findings offer useful guidance, but the best treatment choice depends on your glaucoma severity, eye anatomy, and long-term vision-preservation needs.
