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Glaucoma is a serious eye condition in which three things can happen to the eye if it is not treated:
• The eyeball pressure is higher than normal
• The nerve of the eye is damaged (described as “cupping of the disc”)
• The vision out of the corner of the eye is gradually lost until only tunnel vision is left (field loss).
If the condition is not treated properly, the sight may be lost altogether, and once it is lost no treatment can restore it. Fluid is made continually inside the eye and it filters out through a sievelike band of tissue around the edge of the iris (the coloured part). If the fluid cannot escape fast enough the pressure inside the eye rises. Glaucoma is quite different from high blood pressure. Trabeculectomy is the surgical way of controlling glaucoma in adults. It is not an operation to improve your vision or to restore sight lost because of glaucoma. It is usually done when treatment with drops doesn’t work well enough to keep the pressure in the eye low enough and safe from field loss. Increasingly it is done earlier because it is now known that this operation is more effective than using several sorts of drops over many years.
The operation allows the fluid (the Aqueous) inside the eye to leak out gradually under the outer lining of the eyeball forming a small bubble (bleb). From there the fluid finds its way into the bloodstream. You will be admitted either to Stoke Mandeville Hospital as an in-patient or if you have transport and someone at home, the operation could be done at Milton Keynes Hospital as a day case.
The operation can be performed either under general anaesthetic, where you are put to sleep or under local anaesthetic, where just the eye is numbed but you stay awake. A general anaesthetic is not safe for some people because of other medical problems and carries a very small risk for all. A local anaesthetic is slightly safer for some people, and is no more complicated than a dental injection. The operation takes about 20 minutes, and if you have a local, you have to be able to lie flat and still for that time. But don’t worry, you won’t see any of it going on! In some cases an
antimetabolic drug such as 5-Fluorouxacil may be used to help reduce scarring. The drug is washed off during surgery but occasionally it may cause corneal ulcers, which usually heal post operatively.
Afterwards the eye may be a little sore or irritable for a few days because of two small stitches which dissolve. At first, the operation may work a little too well and the pressure may be very low in the eye. As a result, the front part of the eye may be a little shallow and a little blood may collect, causing blurring of vision especially in the morning. Both these events are common. You may be kept in hospital for observation, but usually both conditions settle without treatment in a few days.
There are two important Don’ts:
• don’t bang or rub your eye you may do serious damage
• don’t lift heavy shopping or do vigorous activity for two weeks.
• keep the eyelids clean with a lint or cotton wool ball moistened with boiled, cool water
• put your eye drops in regularly until told to stop – get more if you run out
• stop using the old glaucoma drops to the operated eye, if you are on glaucoma pills check with the doctor if these are to continue
• tape the plastic shield over your eye at night to prevent accidental damage
• wear glasses to protect the eye but put them on carefully to avoid poking the eye
• report to the hospital or your GP straight away if the eye becomes increasingly painful or if you do bang it and it becomes watery or the vision changes.
• continue the drops to the un-operated eye as before
• ensure that a follow-up appointment has been made two weeks after your discharge from hospital.
• bath or shower but avoid getting soapy water into the eye straight away
• read, write and watch TV as much as you like
• go out and drive if the other eye is good enough, but avoid crowded places or busy public transport because of the risk of bumping the eye
• buy a pair of sunglasses or clip-ons if the light seems too bright.
After the operation you will probably need to be seen twice before new glasses are prescribed after about 8 weeks.
Any operation inevitably causes pressure changes inside the eye and these may result in a small amount of visual field loss. After the operation though, the rate of field loss should be less than before. In patients with severe field damage, surgery can cause a significant amount of field loss. However, an operation may still provide a surer method of preserving vision in the long term even if glaucoma drops need to be restarted.
The advice in this document is intended only as a guide for the benefit of patients, although the exact details of treatment may vary from patient to patient depending on the individual’s condition and any complications arising. It is in line with current practice in ophthalmology.