Glaucoma is a condition which can affect sight, usually due to build up of pressure within the eye.
Glaucoma often affects both eyes, usually to varying degrees. One eye may develop glaucoma quicker than the other.
The eyeball contains a fluid called aqueous humour which is constantly produced by the eye, with any excess drained though tubes.
Glaucoma develops when the fluid cannot drain properly and pressure builds up, known as the intraocular pressure.
This can damage the optic nerve (which connects the eye to the brain) and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
Types of glaucoma
There are four main types of glaucoma:
chronic open-angle glaucoma – this is the most common type of glaucoma and develops very slowly
primary angle-closure glaucoma – this is rare and can occur slowly (chronic) or may develop rapidly (acute) with a sudden, painful build-up of pressure in the eye
secondary glaucoma – this mainly occurs as a result of an eye injury or another eye condition, such as uveitis (inflammation of the middle layer of the eye)
developmental glaucoma (congenital glaucoma) – a rare but sometimes serious type of glaucoma which occurs in very young children, caused by an abnormality of the eye
Glaucoma can be treated with eye drops, laser treatment or surgery. But early diagnosis is important because any damage to the eyes cannot be reversed. Treatment aims to control the condition and minimise future damage.
If left untreated, glaucoma can cause visual impairment. But if it's diagnosed and treated early enough, further damage to vision can be prevented.
Attending regular optician appointments will help to ensure any signs of glaucoma can be detected early and allow treatment to begin.
an ophthalmologist (eye specialist) thinks you are at risk of developing glaucoma
you are over 60 years old
How common is glaucoma?
In England and Wales, it's estimated more than 500,000 people have glaucoma but many more people may not know they have the condition.
Chronic open-angle glaucoma affects up to two in every 100 people over 40 years old and around five in every 100 people over 80 years old.
You are also at increased risk of developing open-angle glaucoma if you are of black-African or black-Caribbean origin.
Some types of glaucoma, such as acute angle-closure glaucoma, are much less common. However, people of Asian origin are more at risk of getting this type of glaucoma compared with those from other ethnic groups.
Symptoms of glaucoma
Symptoms of the different types of glaucoma are explained below.
There are four main types of glaucoma:
chronic open-angle glaucoma – the most common type which often has few symptoms
acute angle-closure glaucoma – which often has severe symptoms
secondary glaucoma – caused by other conditions or eye treatments
developmental glaucoma – a rare condition affecting young babies
Chronic open-angle glaucoma
In cases of chronic glaucoma, there are usually no noticeable symptoms because the condition develops very slowly. People don't often realise their sight is being damaged because the first part of the eye to be affected is the outer field of vision (peripheral vision). Vision is lost from the outer rim of the eye, slowly working inwards towards the centre.
Changes in vision are often linked to getting older, which is why it is so important to have your eyes checked regularly. You should have an eye test at least every two years, or more frequently if your optometrist (healthcare professional who tests sight) recommends it.
Acute angle-closure glaucoma
Acute angle-closure glaucoma develops rapidly. Symptoms are often severe. They include:
redness of the eye
tender eye area
seeing halos or 'rainbow-like' rings around lights
loss of vision in one or both eyes that progresses very quickly
As a result of these symptoms, some people may also feel sick or be sick.
Symptoms of acute glaucoma are not constant. They can last for one or two hours before disappearing again. But each time the symptoms occur, your vision is damaged a little more.
It's important to contact your GP straight away if you have any of the above symptoms, because early treatment can prevent further damage occurring.
If you have symptoms outside your GP's normal working hours, visit your nearest accident and emergency (A&E) department. The healthcare professionals at A&E will relieve the pressure within your eye and treat any pain.
Secondary glaucoma is caused by other conditions, such as uveitis(inflammation of the middle layer of the eye). It can also be caused by eye injuries and certain treatments, such as medication or operations.
It's possible for the symptoms of glaucoma to be confused with the symptoms of the other condition. For example, uveitis often causes painful eyes and headaches.
However, the glaucoma may still cause misty vision and rings or halos around lights.
Recognising the symptoms of developmental glaucoma (also known as congenital glaucoma) can be difficult due to the young age of the baby or child.
However, your child may display symptoms, such as:
large eyes due to the pressure in the eyes causing them to expand
being sensitive to light (photophobia)
having a cloudy appearance to their eyes
having watery eyes
jerky movements of the eyes
having a squint, which is an eye condition that causes one of the eyes to turn inwards, outwards or upwards, while the other eye looks forward
If you notice any of these symptoms, visit your GP or optometrist as soon as possible.
Causes of glaucoma
Glaucoma is caused by a blockage in part of the eye. This prevents fluid draining out of the eye and increases pressure in the eye, called intraocular pressure.
How the eye works
The eyeball is filled with a watery substance called aqueous humour, which creates pressure in the eye to give it shape. In healthy eyes, this fluid constantly flows in and out of the eye. It drains back into the bloodstream at the same rate that it's produced to maintain the correct pressure.
Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked, preventing the aqueous humour from draining properly. An obstruction within the eye, such as a blood vessel blocking the trabecular meshwork, can also prevent fluid from draining properly.
When the fluid cannot drain properly, the pressure in the eye builds up and can damage the optic nerve (the nerve that connects the eye to the brain) and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
It's often unclear why the drainage tubes become blocked or why other parts of the eye obstruct the tubes.
There are a number of things that can increase your risk of developing glaucoma:
age (glaucoma becomes more likely as you get older) – in the UK, chronic open-angle glaucoma affects up to two in every 100 people over 40 years old and around five in every 100 people over 80 years old
ethnic origin – people of African or Afro-Caribbean origin are at increased risk of developing chronic open-angle glaucoma and people of Asian origin are at increased risk of developing acute angle-closure glaucoma
short sightedness (myopia) – people who are short-sighted are more likely to develop chronic open-angle glaucoma
ocular hypertension (OHT – raised pressure in the eye) – your optometrist will be able to diagnose OHT (see diagnosing glaucoma), which increases your risk of developing chronic open-angle glaucoma
family history – if you have a close relative, such as a parent, brother or sister who has glaucoma, you are at increased risk of developing the condition yourself
medical history – people with diabetes may be at increased risk of developing glaucoma