The iStent is a small (1mm long) titanium tube that is implanted into the eye to lower intraocular pressure and reduce the need for eye drops in patients with glaucoma.
It is one of the smallest surgical devices used anywhere in the human body and one of a range of procedures referred to as “Minimally Invasive Glaucoma Surgery (MIGS)”.
Glaucoma is usually due to raised pressure within the eye, which occurs due to reduced drainage of fluid (aqueous humour) through the eye’s natural drainage channels. The iStent is inserted into the eye’s natural drainage channel – the trabecular meshwork. The aqueous humour is then able to drain through the iStent. Insertion of the iStent involves a short surgical procedure that is often done at the same time as cataract surgery, usually as a day case procedure.
The aim of the iStent procedure is to reduce intraocular pressure and reduce the need for glaucoma eye drops. iStent will not cure your glaucoma or reverse any damage to your vision that has already occurred but it may help prevent glaucoma getting worse.
The success rate for this treatment is very promising. A large randomised study in the USA, involving almost 250 patients, randomly assigned patients to have cataract surgery alone or cataract surgery with iStent.
Two-thirds of patients treated with iStent had at least a 20% reduction in intraocular pressure compared to only half of those having cataract surgery alone.
Most patients were able to reduce the number of glaucoma medications they were taking, although some needed to restart glaucoma medications over the next 2 years. A UK study found iStent resulted in a reduction in intraocular pressure from an average of 21 mmHg before surgery to 16.7 mmHg after – an average 30% reduction. As current studies have stopped at 2 years, the long-term success of iStent is uncertain.
Please do note that the iStent is not suitable for all types of glaucoma and is not suitable for all stages of the disease. It is most suited for almost all people with open angle glaucoma.
About the operation
Implantation of an iStent takes only 5 – 10 minutes. It is often performed at the end of cataract surgery but can also be done on its own. The operation is usually performed under local anaesthetic using eye drops to numb the eye (topical anaesthesia).
Please continue any eye drops for your glaucoma as prescribed unless directed otherwise by your ophthalmologist. Please also continue any tablets you normally take. If you take any blood thinning medicines such as warfarin please discuss this with Mr Gazzard.
After the operation your eye will be covered by a protective plastic shield. Please keep the shield over the eye until the morning after surgery. Do not worry about using any eye drops in the operated eye until after removing the shield the morning after surgery. Any eye drops that you use in your other eye must be continued as normal. The morning after your operation you can remove the protective eye shield and gently bathe your eye with cooled boiled water. You can then start the post-operative drops to the operated eye. You will have two types of drop – an antibiotic and a steroid, which will need to be used for approximately 4 weeks after your operation. Please stop your normal glaucoma drops in the operated eye so we will be able to assess the effect of the iStent. You may need to restart these at a later date.
Each time you attend the clinic any changes to your eye drops will be discussed with you. You will usually be reviewed in the eye clinic one day, one week after the operation and then again at around a month later.
The iStent is made from non-magnetic titanium, the same material used for replacing heart valves so it will not cause an allergic reaction or be rejected by the body. As it is non-magnetic it is safe for you to have an MRI scan in the future if needed. The iStent will not set off airport scanners.
The risks of iStent are small. A very small amount of bleeding may occur inside the eye during the operation but this resolves within a few days. You will be given anti-inflammatory and antibiotic eye drops to use after your operation to prevent inflammation and infection.
It is important not to rub or press on your eye after surgery. As this may happen accidentally when you are sleeping please continue to wear the plastic shield over your eye at night for the first week after surgery. Most people need one to two weeks off work after surgery but you many need longer if your work involves heavy lifting or labour. Other activities will depend on whether you have also had cataract surgery. You should avoid the gym for 2 to 3 weeks and swimming for 4 weeks. Depending on vision in your other eye you may be able to drive within a day or two. There are no long-term restrictions after iStent surgery.
If you’d like to know more about iStent, or think that you may benefit from a consultation, please get in touch here.