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.

The 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 (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 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 weakness 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 sight is gradually lost if it is not treated. In the UK, some form of glaucoma affects about 2 in 100 people over the age of 40.

THERE ARE FOUR DIFFERENT TYPES OF GLAUCOMA

• Chronic (= slow) glaucoma: the most common, in which the aqueous fluid can get to the drainage channels, but they slowly become blocked over many years. Eye pressure rises very slowly and there is no pain to show that there is a problem, but the field of vision gradually becomes impaired.

• Acute (= sudden) glaucoma: is much less common in western countries. This happens where there is a sudden and more complete blockage to the flow of aqueous fluid to the eye. This is because a narrow 'angle' closes to prevent fluid from getting to the drainage channels. This can be quite painful and will cause permanent damage to sight if not treated promptly.

• Secondary glaucoma: when a rise in eye pressure is caused by another eye condition. (Note: not covered in this leaflet.)

• Developmental glaucoma: a rare, but sometimes serious condition in babies, which is caused by a malformation in the eye. (Note: not covered in this leaflet.)

ARE SOME PEOPLE PARTICULARLY AT RISK OF CHRONIC GLAUCOMA?

There are several factors which increase the risk:

• Age: it becomes much more common with increasing age. It is uncommon below the age of 40, but affects 1 % of people over this age and 5% over 65.

• Race: People of African origin are more at risk from it and it may come on somewhat earlier and be more severe. Eyes should be regularly tested.

• Family: Eye tests should be done at regular intervals if there is a close relative with glaucoma. All members of the family should be advised to do this. It is especially important over the age of 40 when tests should be done every two years.

• Short sight: People with a high degree of short sight are more prone.

• Diabetes: is believed to increase the risk of developing this condition

WHY CAN CHRONIC GLAUCOMA BE A SERIOUS RISK TO SIGHT?

The danger is that the eye may seem perfectly normal. There is no pain and eyesight will seem to be unchanged, but vision is being damaged. Some people do seek advice because they notice that sight is less good in one eye. 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 as last affected so that, eventually, it becomes like looking through a long tube, so-called 'tunnel vision'. In time, even this would be lost.

HOW IS CHRONIC GLAUCOMA DETECTED?

After the age of 40, eyes should be tested at least every two years and all three glaucoma tests should be requested. These tests are:

• . viewing the optic nerve by shining a light from a special electric torch into the eye

• . measuring the eye pressure using a special instrument

• . being shown a sequence of spots of light on a screen and being asked to say which ones can be seen

The tests are very straightforward, don't hurt and can be done by most high street optometrists (opticians).

HOW IS CHRONIC GLAUCOMA TREATED?

The main treatment aims to reduce the eye pressure. Some treatments also try to improve the blood supply of the optic nerve. Treatment is at the hospital and regular check-ups are required afterwards.

Treatment to lower the pressure usually starts with eye drops. These act by reducing the amount of fluid produced in the eye or by opening up the drainage channels so that excess liquid can drain away. If this does not help, the specialist may suggest either laser treatment of an operation call a 'trabeculectomy' to improve the drainage. The specialist will discuss with you which is the best method for you.

CAN CHRONIC GLAUCOMA BE CURED?

Although damage already done cannot be repaired, with early diagnosis and careful regular observation and treatment, damage can usually be kept to a minimum and good vision can be enjoyed indefinitely.

WHAT IS ACUTE GLAUCOMA?

In acute glaucoma, the pressure in the eye rises rapidly. This is because the periphery of the iris and the front of the eye (cornea) come into contact so that aqueous is not able to reach the tiny drainage channels in the angle between them. Sometimes this is called 'closed angle' glaucoma.

WHAT ARE THE SYMPTOMS OF ACUTE GLAUCOMA?

The sudden increase in eye pressure can be very painful. The affected eye becomes red, the sight deteriorates and may even black out. There may also be nausea and vomiting. In the early stages, misty rainbow-coloured rings around white lights may be seen.

IS ACUTE GLAUCOMA ALWAYS SEVERE?

Sometimes, people have a series of mild attacks, often in the evenings. Vision may seem misty with coloured rings around white lights and there may be some discomfort in the eye. If these attacks are believed to be occurring, a doctor should be contacted without delay. In routine examinations, the structure of the eye may make the examiner suspect a risk of acute glaucoma and advise further tests.

WHAT IS THE TREATMENT?

If an acute attack occurs, attendance at the hospital should be immediate so that the pain and the pressure in the eye can be relieved. Drugs will be given which both reduce the production of aqueous liquid in the eye and improve its drainage. An acute attack, if treated early, can usually be brought under control in a few hours. The eye will become more comfortable and the sight will start to return.

Once the pain and inflammation have gone down, the surgeon will advise making a small hole in the outer border of the iris to relieve the obstruction, allowing the fluid to drain away. This is usually done by laser treatment or by a small operation.

Usually, the surgeon will also advise that the same treatment is performed on the other eye as there is a high risk that it will develop the same problem.

This treatment is not painful. Depending on circumstances and the response to treatment, it may not require admission to hospital. However, sometimes a short stay in hospital may be advised.

CAN ACUTE GLAUCOMA BE CURED?

If diagnosed without delay and treated promptly and effectively, there may be almost complete and permanent recovery of vision. Delay may cause loss of sight in the affected eye. Occasionally, the eye pressure may remain a little raised and treatment is required as for chronic glaucoma.

WHAT ABOUT DRIVING?

Most people can still drive if the loss of visual field is not advanced. To assess possible damage to your peripheral vision, you will need a special test to see whether your sight meets the standards of the Driver & Vehicle Licensing Authority. Ask the specialist about this. The IGA (International Glaucoma Association) leaflet about driving may also be helpful.

Early detection and treatment will usually prevent or retard further damage by glaucoma. Much can be done to help make use of remaining vision as fully as possible. As an optician or optometrist about IOW vision aids and eligibility for registration as partially sighted or blind. Registration opens the door to expert help and, sometimes, to financial benefits.

TO FIND OUT MORE - contact

The International Glaucoma Association (IGA), King's College Hospital, Denmark Hill, London SE5 9RS

10 a.m. - 5 p.m. Monday to Friday - Tel. 0207-737 3265

Produced by -

 INFORMATION ON EYE DISEASES LEAFLET # 1 - (5/2000)