Glaucoma is the name given to a group of eye conditions in which the optic nerve is damaged where it leaves the eye.
What is glaucoma?
Glaucoma is the name given to a group of eye conditions in which the optic nerve is damaged where it leaves the eye. Although any vision which has been lost to glaucoma cannot be recovered, with early diagnosis, careful monitoring and regular use of the treatments, further damage to vision can be prevented and most patients retain useful sight for life. While there are usually no warning signs, regular eye tests will help detect the onset of the disease
Glaucoma is one of the world's leading causes of blindness. In the UK, about two per cent of the population over 40 have the condition.
How glaucoma affects vision
Glaucoma involves loss of vision due to damage of the optic nerve. The optic nerve carries sight images to the brain and any damage to the nerve results in damage to sight.
For the eye to work properly a certain level of pressure is needed for the eye to keep its shape but if the eye pressure gets too high, it squeezes the optic nerve and kills some of the nerve fibres, which leads to sight loss. The first areas to be affected are the off-centre parts of the vision. If the glaucoma is left untreated, the damage can progress to tunnel vision and eventual loss of central vision, although blindness is rare.
Usually, but not always, the damage occurs because pressure within the eye increases and presses on the nerve, which damages it.
Types of glaucoma
There are four main types of glaucoma: primary open angle glaucoma, primary angle closure glaucoma, secondary glaucoma, developmental glaucoma (congenital glaucoma).
Primary open angle glaucoma - This is the most common type of glaucoma and develops very slowly
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.
In England, about 480,000 people have chronic open-angle glaucoma. Among white Europeans, about 1 in 50 people over 40 years of age and 1 in 10 people over 75 years of age have chronic open-angle glaucoma.
You are also at increased risk of developing open-angle glaucoma if you are of black-African or black-Caribbean origin.
The other 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.