Everyone’s eyes are filled with fluid, known as aqueous humour. This fluid helps keep your eyeball in shape and circulates through a tiny meshwork round the edge of your iris. In some people the pressure of the fluid is raised and damages the optic nerve, which carries messages from your eye to your brain. In other people, although the pressure is not raised, there may be a weakness which causes similar nerve damage. In many people it can be a combination of nerve weakness and raised pressure which predisposes them to glaucoma.
Glaucoma affects more than 500,000 people in England and Wales alone.
It principally affects those age 40 and over: 2 per cent of people aged 40+ have glaucoma and this rises to almost 10 per cent of those over 75. People of African or African-Caribbean origin have about four times the risk compared to Caucasians.
In the UK, the most common form of glaucoma is almost always painless, which means that unless you have regular eye checks with an optometrist it can damage your eyesight without you realising. It is the leading cause of preventable blindness in the UK.
Glaucoma can run in families: if you have a close relative with the condition you have four times the chance of developing it, and people aged 40 and over with a close relative with glaucoma are entitled to a free NHS eye examination.
Most of the time when we talk about glaucoma, we mean Primary Open Angle Glaucoma (POAG). This is painless and in the early stage you will have no warning signs. In POAG, the fluid in the eye can flow to the meshwork through which is should drain, but its flow is then restricted. The blockage happens slowly over many years, and the pressure in your eye increases gradually too.
NICE, the National Institute for Health and Clinical Excellence, has issued guidance that people with eye pressure of over 21mmHg should be referred for further investigation. This is the case if the raised pressure is in one or both eyes.
As pressure in the eye typically rises with age, this guidance has been modified so if you are aged 65 and over you should be referred if your pressure is 25mmHg and over, or 26mmHg and over if you are aged 80 plus.
If you have raised pressure and no signs of damage to the nerves in the eye, this is called ‘ocular hypertension’. This could affect between 3 and 5 per cent of people aged 40+, and means that you may be at risk of glaucoma in the future. You will be asked to come back for regular checks and may be offered eye drops to protect your sight.
A smaller number of people have a type of POAG where the pressure is within normal levels. This is known as Normal Tension Glaucoma. It may be due to poor blood circulation around the optic nerve. As with other types of glaucoma, treatment aims to lower the pressure in your eye to a level where the nerves do not suffer further damage.
An uncommon type of glaucoma is acute glaucoma or angle closure glaucoma. This happens when the circulation of fluid round the eye is blocked suddenly. It can be caused by a narrow opening or ‘angle’ between the front of the iris and the drainage meshwork in the eye. It is sudden and painful and can cause permanent damage if untreated. If you experience a sudden painful eye, call NHS Direct for advice on 111.
Glaucoma can be caused by other eye problems: this is known as secondary glaucoma. A very small number of babies are born with a problem that causes the pressure to rise in their eyes. This is known as developmental glaucoma.
For POAG, the most common type of glaucoma in the UK, there are several well known risk factors. You have a higher risk of the condition if:
Most people can’t feel or spot the early changes caused by glaucoma, so how can it be detected? Fortunately, these early changes can be spotted as part of a routine eye examination. Everyone should get their eyes checked at least every two years, and more often if advised. If you have a close family member with glaucoma, the International Glaucoma Association recommends that you are tested for glaucoma from the age of 35 onwards. If you are at higher risk of glaucoma because you are African Caribbean or if you have diabetes mention every time you have an eye test and ask to be checked for glaucoma, whatever your age.
During the eye test the optometrist will carry out some tests to help them get a picture of your overall eye health. They will:
Look at the back of your eye with a light. In glaucoma the ‘optic nerve head’, where the optic nerve joins the eye, changes appearance, which can be seen using an ophthalmoscope
Measure the pressure in your eye – this can be done using an instrument that blows a puff of air on the eye or using a small probe that rests gently on the surface of your eye
Check your field of vision – you will be asked to put your chin on a rest and look at a screen where small spots of light will flash up one after another
If the optometrist spots signs of glaucoma they will write a letter explaining this to your GP. Your GP will then pass these details on to the hospital eye department. You will be sent an appointment to see an ophthalmologist, a specialist eye doctor.
NICE recommends that to diagnose glaucoma, the ophthalmologist should:
Glaucoma can be treated. There are various different drugs – mainly eye drops – that can help you. However, if your sight has been damaged there is not yet a treatment that can regain your lost vision. Treatment can only protect the vision that you have. The International Glaucoma Association estimate that around 95 per cent of those diagnosed early with glaucoma in the UK will retain useful sight for life. The main treatments for glaucoma are eye drops, laser treatment and drainage surgery.
Eye drops help your eyes by opening up the drainage meshwork in your eye or reducing the amount of fluid produced: in this way the pressure in your eye goes down.
If eye drops alone do not drop the pressure enough to prevent continuing visual field loss you may also be offered laser treatment. This can be used to improve the drainage of fluid from your eye and lower the pressure.
Drainage surgery, also known as trabeculectomy creates a channel that the fluid in the eye can drain out through. You may need to use eye drops too after surgery.
At the appointment you should have the chance to talk about your diagnosis, and ask about what might happen in the future. The eye specialist should explain that glaucoma is usually symptom less and you need to keep coming back to have it monitored. You will be told to persist with your treatment as it is needed to protect your sight. After your initial appointment, if you are prescribed eye drops you will be invited back within a few months to check that the drops are having the necessary effect. If everything progresses well you will continue to use your eye drops and have checks at regular intervals, every 6 months or annually depending on what your consultant advises. If you are given eye drops you will need to continue to use these for life unless the specialist changes your treatment or suggests laser treatment or surgery.
If you are confused by any of the terms used during your appointment or want to find out more, the International Glaucoma Association has an excellent glossary on their website and can also answer questions through their Sightline, on 01233 648 164. www.glaucoma-association.com
Once you have glaucoma you will get your eyes checked at the hospital on a regular basis. The hospital specialist will let you know if the damage to your eyes is enough to cause problems with driving. The International Glaucoma Association offers a useful leaflet about driving when you have glaucoma.
If you already have sight loss due to glaucoma there are a number of ways to help you make the most of the vision that you do have. Ask at the hospital appointment to talk to a low vision specialist who can advise you on aids to help. A rehabilitation officer can advise and help you too.
If you care for someone with sight loss due to glaucoma, be aware that moving around is the area that they are most likely to have problems with. When crossing the road, they will need to make a point of turning their head and using their hearing to double check for cars.
Inserting eye drops can cause problems for older people and anyone with arthritic fingers. There are various eye drop dispensers available to make the process of inserting eye drops much easier. These are available through the RNIB shop: see contacts for details of ways to get in touch.