Glaucoma is a term that describes a group of eye conditions that affect vision. Glaucoma often affects both eyes, usually in varying degrees. One eye may develop glaucoma quicker than the other.
Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked. This prevents eye fluid (aqueous humour) from draining properly.
When the fluid cannot drain properly, pressure builds up. This is called 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 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) – this is rare but can be serious. It is usually present at birth or develops shortly after birth. It is caused by an abnormality of the eye
Glaucoma can be treated with eye drops, laser treatment or surgery. However, 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 is 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.
You are entitled to a free NHS eye test if you are over 40 years old and have a first-degree relative (mother, father, sister or brother) with glaucoma.
You may also be entitled to a free NHS eye test if:
an ophthalmologist (eye specialist) thinks that you are at risk of developing glaucoma
you are over 60 years old
Read more information about NHS eye care services.
How common is glaucoma?
In England, about 480,000 people have chronic open-angle glaucoma. Among white Europeans, about one in 50 people above 40 years old and one in 10 people above 75 years old has chronic open-angle glaucoma. It may be more common among people of black-African or black-Caribbean origins.
The other types of glaucoma are much less common. Among white people, acute angle-closure glaucoma may affect about one in 1,000 people. It is more common among people of Asian origin, affecting around one in 100 of them.