TUBE SHUNT FOR GLAUCOMA
Glaucoma is the name for a group of eye conditions which cause damage to the optic nerve at the back of the eye. The naturally made fluid in the eye is unable to drain away properly which can result in a build up of pressure within the eye. The pressure is usually treated with eye drops. If the eye drops fail to reduce the pressure, damage to the optic nerve will cause permanent loss of sight. To lower the eye pressure a surgical procedure known as a Tube Shunt operation can be carried out. Tube shunt operation is often chosen if Minimally Invasive Glaucoma Surgery or Trabeculectomy has failed or is likely to fail because the function of the operation is less dependent on the degree of scarring of the conjunctiva.
What is an aqueous tube shunt?
An aqueous shunt or tube is a tiny device that is used to decrease the pressure inside the eyes of people with high eye pressure or uncontrolled glaucoma (see photographs below). The device is put into the eye during an operation that allows excess aqueous humour (fluid inside the eye) to drain. Your surgeon will place a plate towards the back of your eye where it will form the small blister or ‘bleb’ where the fluid will drain to. You cannot see the bleb as it is too far back behind your eye to see. By draining away the excess fluid inside the eye, the amount of pressure within the eye is reduced. You can’t feel the bleb and tube, and you cannot feel the fluid flowing through them.
What happens during the operation?
The tube operation usually takes around 45 minutes under a local anaesthetic or 90 minutes under general anaesthetic. During the operation, your surgeon will insert a small silicon tube (less than 1 mm in diameter) into the front chamber of your eye. It is so small you would need a microscope to see it. To stop the tube from moving around and becoming exposed through the conjunctiva, your surgeon will stitch a patch made from donor eye tissue onto the surface of your eye, over the tube. The donor tissue comes from the transplant service after tests for infections. Sometimes the surgeon may use a suture to stop too much fluid draining during the first few months. This means that your eye pressure could still be high until this suture has been removed.
What do I need to do to prepare for the operation?
You will attend the day ward for approximately a whole day so that we can prepare you for and perform the operation, then observe you afterwards. Sometimes you may need to stay overnight. The treatment will take place in one of our theatres. The operation can be performed under local anaesthetic (where the eye is numbed) or general anaesthetic (you will be asleep). The type of anaesthetic used depends on the surgeon and the patient, and we will discuss this with you. This means that you will have to follow special instructions before you come into hospital. The nurses in the pre-assessment clinic will advise you of any special instructions you need to follow.
What are the risks?
Some of the risks involved are:
• For a period of time pressure in the eye may become too high or too low. If eye pressure is too high, your surgeon will help you reduce pressure with adjustment or removal of stiches. If eye pressure is too low (<5 mmHg), then often your surgeon would manage with conservative methods first but occasionally will require return to theatre for injection of a material that can improve eye pressure.
• In some cases a cataract may develop (~10%). This can be treated by an operation if necessary.
• Serious complications are rare, but very rarely the sight can get worse after the operation and not recover especially in the setting of advanced glaucoma.
What happens before the operation?
You should continue to take any eye drops and tablets for your glaucoma as
prescribed until the time of your surgery, unless you are told not to use
them. You may be asked to use a new eye drop four times a day in the eye
that will be having surgery, for four weeks before the operation.
If you are taking any blood thinning tablets (such as warfarin or aspirin) they
may increase the risk of bleeding during the operation. You should discuss
this with your glaucoma specialist.
You will be given instructions about eating and drinking before the operation
in your operation appointment letter.
How long does it take?
The operation usually takes about two and a half hours to perform.
What happens after the operation?
After the operation, you will be taken to the recovery area where you will
wake up. In the recovery area, nursing staff will look after you, checking
your blood pressure and pulse, and giving you pain relief medication, if
Immediately after your operation, your eye will be covered by an eye pad
and protective plastic shield.
Once the nurses are happy that you have completely recovered from the
operation and general anaesthetic, you can go home. We will give you all
the medications you need. The team will make an appointment for you to be
reviewed the next day with your glaucoma specialist.
What can I expect after tube-shunt surgery?
The eye pad and shield will be taken off at your glaucoma specialist's office the morning after your operation.
Your eye will be a bit gritty and sore for at least a few days. After your eye has settled down, the tube is usually not visible. As the tube remains inside your eye, try not to rub your eyes as this might cause the tube to move and damage other parts of the eye.
What should I look out for at home?
If you have any of the following after tube shunt surgery:
• Reduced vision or loss of vision.
• Severe pain that does not go away.
• Any abnormal discharge from your eye, especially if it is increasing.
Activity after Surgery
It is very important to avoid strenuous activity during the early post-operative
period including weight lifting, swimming, tennis, jogging and contact sports.
You can watch television and read, as these will not harm the eye. For patients who
wish to pray, it is better to kneel but do not to bow the head down to the floor in the
first 2 – 3 weeks. Bending over can cause significant pain when the eye is still
inflamed after surgery. Activities such as yoga that require head-down posturing
should be avoided. As you will be monitored closely following surgery, you can consult your surgeon before starting any strenuous activity. If the eye pressure is very low after surgery the surgeon may suggest refraining from all exertion and resting until the pressure is restored.
When is the eye back to normal?
In most cases, it takes 2 to 3 months for the eye to feel completely normal and sometimes longer in more complicated cases. A spectacle test can be performed after 3 months as the spectacle prescription may have changed slightly from the pre-surgery prescription.