What Is iStent Glaucoma Surgery?
Glaucoma is a group of eye conditions in which the optic nerve becomes damaged, often, though not always, in association with raised intraocular pressure. In open-angle glaucoma, fluid produced inside the eye drains too slowly through the natural drainage tissue, known as the trabecular meshwork, causing pressure to build gradually and painlessly.
The iStent is a very small titanium stent, one of the smallest medical devices implanted in the human body. It is placed through the trabecular meshwork into Schlemm’s canal, creating a bypass channel that may allow fluid to drain more efficiently and help reduce eye pressure. Newer versions, such as the iStent inject W, involve two stents placed at different points around the drainage angle.
This is a surgical, pressure-lowering treatment rather than a cure. It does not reverse existing optic nerve damage, but it may help slow further progression by improving pressure control. The National Institute for Health and Care Excellence (NICE) has published guidance on glaucoma management and on trabecular micro-bypass stent procedures, and treatment decisions in the UK are generally guided by this alongside advice from the Royal College of Ophthalmologists.
Where It Fits in the Treatment Pathway
Glaucoma care usually begins with pressure-lowering eye drops or laser treatment such as selective laser trabeculoplasty. MIGS procedures like the iStent are often considered when drops are not tolerated, are difficult to instil, or are not providing sufficient pressure control, particularly in patients who also have visually significant cataracts. More traditional filtration surgery, such as trabeculectomy or tube surgery, may be more appropriate for advanced or rapidly progressing disease.
Who May Benefit From This Treatment?
iStent glaucoma surgery may be considered for adults with mild to moderate open-angle glaucoma or ocular hypertension whose eye pressure needs further lowering. It is most commonly performed in combination with cataract surgery.
You may wish to discuss an assessment if you experience any of the following:
- A diagnosis of open-angle glaucoma or raised eye pressure requiring ongoing drops
- Difficulty using eye drops reliably, or side effects such as redness, stinging, allergy or dry eye
- Blurred or misty vision, glare or halos suggesting cataract as well as glaucoma
- Eye pressure that remains above your target level despite treatment
- Evidence of gradual visual field or optic nerve change on monitoring
The iStent is not suitable for everyone. It is generally not used in angle-closure glaucoma, certain secondary glaucomas, or advanced disease where a larger pressure reduction is required. Suitability depends on examination of the drainage angle, the stage of your glaucoma and your overall eye health, and Ms Diana Urbaneja will discuss the alternatives that apply to your situation.
Conditions Commonly Assessed
- Primary open-angle glaucoma
- Ocular hypertension with risk factors for progression
- Cataract occurring alongside glaucoma
- Intolerance or poor response to glaucoma medication
- Pseudoexfoliation and other secondary open-angle glaucomas, in selected cases
Potential Benefits
Outcomes vary between individuals, and no procedure can guarantee a particular result. Where treatment is successful, patients may experience:
- A reduction in intraocular pressure
- A reduced need for glaucoma eye drops, or fewer different medications, in some cases
- Improved comfort for those affected by drop-related side effects
- Clearer vision when combined with cataract surgery and a premium or standard intraocular lens
- Support for long-term glaucoma control, which may help limit further optic nerve damage
- A less invasive alternative to traditional filtration surgery, with a generally quicker visual recovery
Some patients still require drops after surgery. Continued monitoring remains essential regardless of the outcome.
Consultation and Assessment
A thorough assessment is carried out before any decision is made. This typically includes:
- A discussion of your symptoms, family history, general health and current medications
- Measurement of intraocular pressure and corneal thickness
- Slit-lamp examination and gonioscopy to inspect the drainage angle
- Optic nerve imaging with OCT and visual field testing
- Biometry and lens measurements if cataract surgery is planned
- A clear explanation of the benefits, risks and alternatives, followed by a personalised plan
You will have time to ask questions before giving informed consent. Where a different approach, such as laser, a change of medication, or filtration surgery, is more appropriate, this will be recommended instead.
How the Procedure Is Performed
iStent surgery is normally a day-case procedure performed under local anaesthetic, often with eye drops and an injection around the eye. Sedation may be offered if you feel anxious.
The surgeon makes a tiny incision, usually the same one used for cataract removal. Using a specialised microscope lens to view the drainage angle, the stent or stents are placed precisely into the trabecular meshwork. The additional time required is generally only a few minutes on top of routine cataract surgery. No stitches are usually needed, and you go home the same day with a protective shield and a course of anti-inflammatory and antibiotic drops.
Recovery and Aftercare
Vision is often blurred for the first few days and may fluctuate for a few weeks. Most people manage daily activities quickly, though you should avoid rubbing the eye, swimming, heavy lifting and dusty environments until advised otherwise. You will be given guidance about driving and returning to work based on your recovery.
Follow-up appointments are arranged in the days and weeks after surgery to check pressure, healing and whether your glaucoma medications can be adjusted. Long-term monitoring with pressure checks, imaging and visual fields continues afterwards. Seek prompt advice if you develop increasing pain, marked redness, sudden loss of vision or discharge.
01
Consultation
Suitability assessment
02
Surgery
iStent implantation, often with cataract surgery
03
Aftercare
Pressure checks & drops
Guide Price
Price TBC
Often combined with cataract surgery. See the pricing page for all options.
At a glance
Anaesthetic
Local
Procedure time
~30-45 min
Stay
Day case
Recovery
1-2 weeks
Follow-up
Regular pressure monitoring