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.