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Glaucoma drainage surgery (trabeculectomy)

What is glaucoma?

Glaucoma is a condition causing damage to the optic nerve at the back of the eye. It is usually, but not always, associated with a rise in pressure in the eye. There are several different types of glaucoma.

Glaucoma causes loss of vision by causing pressure on the optic nerve which carries the visual signals from the eye to the brain. Glaucoma causes gradual permanent loss of vision. Once vision has been lost, it cannot be restored. The only way we know how to prevent loss of vision is by reducing the pressure. If the pressure within the eye is not kept at a satisfactory level, the condition is likely to progress and visual loss will continue.

The eye pressure is usually controlled with eyedrops. You will have been offered glaucoma surgery because it is felt that the pressure within your eye cannot be controlled by using drops.

What is the treatment?

Drops are usually the first treatment to control pressure and laser may be attempted. Not all patients respond to these measures. There is some evidence that suggests that surgery is the most effective way of keeping the pressure down and is best performed early in the course of the disease.

The operation is usually done under local anaesthetic. An injection is given around the eye to freeze it and to stop it moving. A flap valve is made in the white of the eye (the sclera ) under the upper eyelid. This allows fluid to drain away from the inside of the eye under the loose skin which covers the eye (the conjunctiva). Sometimes a chemical is applied to the eye for a few minutes to minimise the healing of the valve. After the operation you may see a small blister of fluid on the eyeball under the upper lid. You should be allowed to go home but you will need to be examined the following day in the clinic.

What to expect after the surgery

On the first day, the eye will be red and may be uncomfortable. The vision may be unchanged or it may be blurred. This will settle over the first few weeks. You will be asked to apply some drops for a few weeks after surgery to minimise the inflammation of the eye after surgery. The blurred vision may last for a few weeks after surgery. After it should get back to its previous level. It should be remembered that this operation is not designed to improve your vision but aims to prevent further visual loss.

Post-operative advice

For the first week after surgery, you should take life fairly easy and avoid doing anything strenuous. Do not rub the eye or use an eye bath until told that it is safe. You may wash your face and hair but take care not to get water in the eye for the four weeks after surgery. Lifting, heavy work and running should be avoided for at least two weeks after surgery. Swimming should be avoided for four weeks.

The use of contact lenses is not advised after this type of surgery.

Complications of surgery

The surgery is delicate and complications may occur but they are rare.

The pressure within the eye may be lower or higher than expected in the early post operative period. The post operative treatment may need to be modified if this is the case.

Haemorrhage may occur during and after surgery. Blood may collect in the front compartment of the eye which usually disappears after a few weeks. Very rarely, haemorrhage collects beneath the retina and this may lead to permanent visual loss.

Infection is rare and occurs in less than 1 in 1000 cases. It may however cause serious visual loss.

Cataract may make a pre-existing cataract worse. If it does so, the vision may be restored with cataract surgery.

Despite rigorous attention to surgical detail and taking all necessary precautions, glaucoma surgery may not be successful in some patients. This is usually caused because the body's healing response heals over the flap that has been made. If this does happen, you may be asked to start taking drops again or you may be offered another operation.

If you have any questions regarding this information, please ask your eye doctor.


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