iStent is one surgical option for open angle glaucoma.
It is sometimes called 'trabecular stent bypass microsurgery'.
High pressure in the eye
In a healthy eye, as new fluid flows into the eye, the same amount should drain out. This keeps the pressure in the eye (called ‘intraocular pressure’) stable.
If the drainage is not working properly, fluid builds up. This increases in the pressure in the eye.
High eye pressure with no nerve damage is called ‘ocular hypertension’.
Eventually, this can lead to glaucoma. This is when the high pressure causes damage to the optic nerve. This is the nerve that connects the eye to the brain.
Glaucoma can lead to permanently losing part of your vision. Symptoms can develop slowly. Eventually, without treatment, it can make you blind.
In patients with glaucoma or ocular hypertension, lowering the eye pressure may prevent symptoms getting worse.
iStent
An iStent is a tiny tube made of titanium. It creates a small opening in the drainage channel inside your eye. This allows fluid to flow out, reducing the pressure. Two iStents are used in the affected eye.
This iStent is safe in an MRI scan and does not set off the airport security systems.
What the operation involves
The iStents are usually inserted during cataract surgery. Occasionally they are done in their own operation. It is done as day surgery.
If more than one eye requires iStent surgery, they will be done on separate dates.
Most cases are done with local anaesthesia, so you are awake throughout. You are given eye drops to numb the eye. Then, once you are in the operating theatre, you are given anaesthetic injections.
You should feel comfortable throughout the procedure. If needed, you can be given medicines to make you feel relaxed and sleepy.
Towards the end of the procedure, we will tilt your head and put a special contact lens on the eye. This is to view the drainage angle in the eye.
The iStents are placed using a special device through the same cut used during the cataract surgery. You may feel a slight pressure sensation when they are inserted.
At the end of the procedure, we will put a dressing pad and a clear plastic shield over the operated eye. If your other eye has poor vision, we will remove the cotton pad and leave just the clear shield before you go home.
As the local anaesthetic takes a few hours to wear off, your eyesight will be blurred for a few hours. You should not drive yourself home. You should be collected or go home on public transport.
Risks
Complications are uncommon. They can occur during the operation or afterwards in the healing period.
The risks of combined iStent and cataract surgery are similar to the risks of cataract surgery alone.
Minor problems such as a small amount of bleeding and inflammation can occur. These usually get better over the first few days.
Eye pressure can increase if the stent becomes blocked or becomes less effective with time. If this occurs, treatment with further medications or surgery may be needed.
Alternative options
Alternative treatments to an iStent include eye drops, laser treatment or surgery. These all aim to lower the pressure in the eye.
Eye drops
Most patients respond well to eye drops but side effects may develop with time. Occasionally, they may not do enough to reduce the eye pressure.
Laser
‘Selective laser trabeculoplasty’ (SLT) is also an effective way to lower the eye pressure.
Surgery
Surgical options include the following. Please refer to other leaflets for further information about these treatments or ask your doctor.
There are various ‘Minimally Invasive Glaucoma Surgery’ (MIGS) options. One of these is the iStent.
MIGS procedures can be done in combination with cataract surgery so offer a good option for glaucoma patients with cataracts.
Traditional glaucoma surgery includes ‘trabeculectomy’ and ‘aqueous shunt insertion’. Compared with MIGS, traditional surgery can be more effective at controlling the eye pressure but it is a bigger operation and takes more time to recover from.
What happens afterwards
Eye drops
After the surgery, you will be given eye drops to reduce inflammation and prevent infection.
If you are currently on glaucoma drops, you should continue with them too.
Once your eye settles from the surgery the eye pressure should reduce. We will tailor or stop your glaucoma medications, depending on the individual response.
Follow-up
We will arrange follow-up depending how the surgery goes on the day. We will usually see you again within 3 to 4 weeks of the surgery.
When to contact us
Contact the Acute Referral Clinic (ARC) immediately if:
your eye pain gets worse
your eye pain is associated with headache, nausea and vomiting.
your eye becomes very sticky
your vision becomes increasingly worse or blurred.
Contact the ARC on 020 8934 6799, Monday to Friday, 8:30am to 4:30pm.
If you have any concerns outside of these hours, contact one of these alternative emergency eye services.
St George’s Hospital, Tooting Duke Elder Ward Monday to Friday, 6pm to 8:30am 24 hours weekends You will need a referral from your emergency GP to be seen.
Moorfields Eye Hospital, City Road, Old Street 24-hour emergency care Walk-in service, no referral needed.
Western Eye Hospital, Marylebone Road 24-hour emergency care Walk-in service, no referral needed.
