Patient Information

Eye surgery leaflets

Colchester Eye Centre
Colchester Primary Care Centre
Tel: 07780 005 814
Monday to Friday, 9am to 5pm


iStents for open angle glaucoma


This leaflet will you help understand the iStent, which is one option for managing your open angle glaucoma.

The iStent procedure is performed at the same time as cataract surgery when two identical tiny iStents are implanted in the eye to help reduce your eye pressure.


Open angle glaucoma and intraocular pressure

Glaucoma is a group of diseases that damage the eye’s optic nerve and can, if left untreated, cause vision impairment and even blindness. Open angle glaucoma occurs with no noticeable symptoms and can often go undiagnosed, and worsen in time if not treated. The iStent is inserted only in patients with this type of glaucoma.

Your eyes produce a liquid called aqueous humor, which is essential for healthy eyes. Often in glaucoma this liquid does not flow out of the eye properly, and the pressure in your eye increases. This
increased pressure can damage your optic nerve.

When you come to clinic we measure your eye pressure. This is important because most people with open angle glaucoma have no early symptoms or eye pain. If left untreated, over time it may result in permanent vision loss and blindness.


The iStents

The iStents are two tiny metal devices designed to stay in place inside the eye and allow drainage of liquid.

During cataract surgery the iStents will be placed closely together inside your eye to help reduce your eye pressure.

These are not visible outside the eye, and cannot cause any symptoms.

The iStents will not cure your open angle glaucoma but will help to slow down any progression.


Cataract surgery with iStent

A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Symptoms of cataracts may include cloudy or blurry vision, colours that seem faded, difficulty with glare such as sunlight and oncoming headlights, and a more frequent change of glasses.

Cataract surgery involves the removal of the cloudy natural lens and replacement with an artificial (intraocular) lens. When you have cataract surgery along with the iStent as part of a single operation, the two stents are implanted in your eye immediately after your cataract is removed and the artificial lens is implanted.


Before your operation

Your eye will be examined before your operation.

Measurements of your eye and eye pressure will determine which type of artificial lens is best for you.

Depending on which medications you are taking, you may be asked to stop taking them for a few days before your operation or you may be asked to start new medications.


During your operation

You will have a local anaesthetic so you will be awake during the operation.

You will not be able to see what is happening but you may be aware of a bright light.

You will not be able to feel anything.

During the operation you will be asked to keep your head still and lie as flat as possible.

The operation takes approximately 45 minutes.

The surgeon makes a very small cut in the eye, softens the lens with sound waves and removes it through a small tube.

The back layer of the lens capsule is left behind.

The artificial implant is inserted to replace the cataract.

Immediately after the cataract portion of the surgery is completed, the surgeon will implant the two iStents.


After your operation

After the operation, an eye pad or shield will be placed over your eye to protect it.

You will spend a short time in the recovery area and then you will be able to go home to recover.

It is important that you have someone to take you home as you will not be able to drive.

You will be given instructions by the nurses regarding the removal of the eye pad the next day.

You will also be given instructions regarding your next appointment.

After your operation you will be given an implant card containing important information related to the iStent. You should keep the card safe.

If you need an MRI scan in the future you will need to show the doctor your implant card; although made of titanium, iStent is considered to be MRI safe with current machines.

You will be monitored after your surgery to make sure your eye pressure is controlled.

If needed we will recommend additional therapy, including appropriate medication or other treatments to control your eye pressure.



The iStent lowers the eye pressure, which helps in the management of your glaucoma and delays any disease progression.


Potential risks

The risks of iStent with cataract surgery are similar to the risks of having cataract surgery alone.

There are, however, some additional risks associated with iStent, and these will be discussed with you
before your operation.

There is a small risk that the stents may not be implanted successfully or not implanted in the planned position.

The stents may become blocked over time, and in rare cases, you will need a second operation to clear the blockage.

Quite often, microscopic bleeding occurs inside the eye following correct placement of iStents, and this actually tells us the implantation was successful. However, it can cause temporary hazy vision but this will resolve itself.

Although uncommon, there are other risks that may be related such as excessive bleeding during surgery and inflammation and progression of your glaucoma.

General risks of eye surgery include reactions to medicines, back of the eye bleeding, infection,
inflammation, vision changes, increased eye pressure, and swelling of the cornea.


After surgery

You will be given eye drops to help your eye heal with specific instructions on how to use them.

You may be given some antibiotics to prevent infection.

You will usually be examined a month after your surgery to check your eye pressure, which may change during the first several days after surgery. Sometimes a day one pressure check may be required.


Post-operative instructions

  • No rubbing or pressing on the eye after the operation. As this can happen when you are sleeping we will ask you to continue wearing the plastic shield at night for a few weeks.
  • Reading, watching television and using the computer are fine.
  • Do not drive until the doctor tells you it is OK to do so.
  • Most people need 1 to 2 weeks off work after the operation.
  • Keep the eye dry for two weeks. This is to reduce the risk of infection.
  • Please ensure you wear goggles when swimming.
  • It is safe to fly after the operation.


Please ring the Eye Clinic on the numbers listed if you have any problems such as reduced vision, painful red eye or discharge after your surgery for advice and support.


Your experience matters

We value your feedback. Please help us improve our services by answering a simple question, in our online survey – “Overall, how was your experience of our services?”

This survey is known as The Friends and Family Test.



The Recite feature on this website attempts to provide digital accessibility and translation support. If you would like to make a request for a leaflet to be produced in a different format please see our PALS contact page in order to contact the team and make a request. If you require a translation please see our translation information page. ESNEFT are actively attempting to achieve accessibility regulation compliance under the Public Sector Bodies (Websites and Mobile Applications) (No.2) Accessibility Regulations 2018.

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