The iStent is designed to reduce intraocular pressure safely and effectively in patients diagnosed with primary open-angle glaucoma, pseudo-exfoliative glaucoma or pigmentary glaucoma. It may not be suitable for some types of glaucoma and your consultant will discuss with you whether this procedure is suitable for you.

The device may also be implanted in patients who continue to have elevated intraocular pressure despite prior treatment with glaucoma medications and conventional glaucoma surgery.

Glaucoma is commonly associated with increased pressure in the eye. To help control this pressure, one or two tiny iStent are gently inserted into your eye. Implanted at the time of cataract surgery, or in a separate procedure, they create bypasses, or openings, between the front part of the eye and its natural drainage pathway restoring your eye’s natural ability to drain fluid. Once inserted, you will not be able to see or feel the stents, but they will be working to help reduce your eye pressure.

Implanting the iStent has a number of benefits including:

• Unlike eye drops, which require regular doses, iStent is a medical device that is designed to work continuously.

• iStent may help reduce the number of glaucoma medications needed at your doctor’s discretion.

The iStent is made from non-magnetic titanium; the same material used for replacing heart valves, so it should not be rejected by the body or cause an allergic reaction. It will not set off airport scanners and will not cause any problems if you need to have an MRI scan.

No. iStent aims to prevent your glaucoma getting worse by lowering your eye pressure. It will not cure your glaucoma, or reverse any damage already caused by glaucoma or bring back any lost vision.

As with all eye surgery, it carries small risk of reduced vision or a loss of vision, pain, bleeding, infection and inflammation in the eye.

A very small amount of bleeding inside the eye occurs during the operation but this resolves within a few days. If the iStent fails to lower your eye pressure it will not create any additional harm to your eye.

There could be a risk of the stent becoming blocked or coming out of position. It may not provide long term glaucoma control and there may be failure or loss of effect with time (as this is a relatively new procedure, long term data is not available).

When NICE (National Institute of Care and Clinical Excellence) looked at the evidence, it decided that there was enough evidence to show that it is safe enough and works well enough for use in the NHS. The 8 studies that NICE looked at involved a total of 3,096 patients.

The studies showed that a small number of people had problems after the procedure, and some of these were serious. The risks included:

• Significantly worse vision after the procedure in 1 patient and decreased vision in 7

• increased pressure in the eye in up to 50% of patients in 1 of the studies

• bleeding in the eye in about 2% of patients

• damage or changes to structures in the eye in about 2% of patients

• dry eye in about 2% of patients

• the stent not in the correct place in 2 to 18% of patients

• the stent becoming blocked in 4 to 15% of patients

• some people needing a second procedure to reposition the stent or to insert a replacement stent.

If you want to know more about the studies, see the NICE guidance at https://www.nice.org.uk/guidance/ipg575

The operation is usually performed under a local anaesthetic, meaning that you are awake but your eye is numb so you will not feel anything.

The iStent is implanted through a small, self-sealing incision in the clear part of the eye (cornea) using a small inserter, and can be performed at the same time as a cataract surgery or by itself. Once implanted, the iStent can work immediately.

At the end of the procedure, your operated eye will be covered with a pad and/or protective shield, which you might also be instructed to wear at night for a few days as a precautionary safety measure to protect your eye.

iStent surgery and cataract surgery is usually completed as a day case, meaning that you should be able to go home the same day, but you will not be able to drive so you are advised to have someone collect you from the hospital.

Immediately after the procedure your vision in the operated eye might be blurry for one to two weeks, and your eye might be slightly bloodshot for a few days.

You will be prescribed antibiotic and anti-inflammatory eye drops to prevent infection and inflammation, which you should take as prescribed.

Your eye doctor will inform you if or when you can stop taking any glaucoma eye drops. Do not stop taking your drops in either eye, unless specifically instructed to do so by your eye doctor.

It is very important that you do not bump, rub or press on your eye after surgery. And you should also avoid swimming for four weeks until your wound has healed.

You may need to be off work for one to two weeks and possibly longer if you work in a dusty or dirty environment.

There are no long-term restrictions following iStent surgery. You may carry on your activities as normal.