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GLAUCOMA
GLAUCOMA


What is glaucoma?

Glaucoma is the name for a group of eye conditions in which the optic nerve is damaged at the point where it leaves the eye. This nerve carries information from the light sensitive layer in your eye, the retina, to the brain where it is perceived as a picture.  Your eye needs a certain amount of pressure to keep the eyeball in shape so that it can work properly. In some people, the damage is caused by raised eye pressure. Others may have an eye pressure within normal limits but damage occurs because there is a weakness in the optic nerve. In most cases both factors are involved but to a varying extent. Eye pressure is largely independent of blood pressure.

What controls pressure in the eye?

A layer of cells behind the iris (the coloured part of the eye) produces a watery fluid, called aqueous. The fluid passes through a hole in the centre of the iris (called the pupil) to leave the eye through tiny drainage channels. These are in the angle between the front of the eye (the cornea) and the iris and return the fluid to the blood stream. Normally the fluid produced is balanced by the fluid draining out, but if it cannot escape, or too much is produced, then your eye pressure will rise. (The aqueous fluid has nothing to do with tears.)

Why can increased eye pressure be serious?

If the optic nerve comes under too much pressure then it can be injured. How much damage there is will depend on how much pressure there is and how long it has lasted, and whether there is a poor blood supply or other weaknesses of the optic nerve. A really high pressure will damage the optic nerve immediately. A lower level of pressure can cause damage more slowly, and then you would gradually lose your sight if it is not treated.

How common is glaucoma?

In the UK some form of glaucoma affects about 2 in 100 people over the age of 40.

 

Are some people particularly at risk of chronic glaucoma?


Yes there are several factors which increase the risk.


Chronic glaucoma becomes much more common
with increasing age. It is
uncommon below the age of 40
but affects two per cent of people over this
age and five per cent over 65.  
If you are of African origin you are more at risk of chronic glaucoma and it may come on somewhat earlier and be more severe. So make sure that you have regular  tests.  If you have a close relative who has chronic glaucoma then you should have eye  tests at regular intervals. You should advise other members of your family to do the same. This is especially important if you are aged over 40 when tests should be done every year.  People with a high degree of short sight are more prone to chronic glaucoma.  Diabetes is believed to increase the risk of developing this condition.

Why can chronic glaucoma be a serious risk to sight?

The danger with chronic glaucoma is that your eye may seem perfectly normal. There is no pain and your eyesight will seem to be unchanged, but your vision is being damaged. Some people do seek advice because they notice that their sight is less good in one eye than the other.  The early loss in the field of vision is usually in the shape of an arc a little above and/or below the centre when looking 'straight ahead'. This blank area, if the glaucoma is untreated, spreads both outwards and inwards. The centre of the field is last affected so that eventually it becomes like looking through a long tube, so called 'tunnel vision'. In time even this sight would be lost.

How is chronic glaucoma treated?

The main treatment for chronic glaucoma aims to reduce the pressure in your eye. Some treatments also aim to improve the blood supply to the optic nerve. You will need to go to hospital for treatment and have regular check-ups afterwards.

Treatment to lower the pressure is usually started with eyedrops. These act by reducing the amount of fluid produced in the eye or by opening the drainage channels so that excess liquid can drain away. If this does not help, your specialist may suggest either laser treatment or an operation called a trabeculectomy to improve the drainage of fluids from your eye. Your specialist will discuss with you which is the best method in your particular case.

This information has been reproduced with the kind permission of the RNIB and the Royal College of Ophthalmologists.