Glaucoma types and overview
Glaucoma is a group of eye conditions affecting a person's vision, usually linked to a build-up of pressure inside the eye.
Glaucoma is estimated to affect around 500,000 people in England and Wales.
The increased pressure, called intraocular pressure, can damage the optic nerve, which transmits images to the brain. If damage to the optic nerve from high eye pressure continues, glaucoma will cause loss of vision. Without treatment, glaucoma can cause total permanent blindness within a few years.
Because most people with glaucoma have no early symptoms or pain from this increased pressure, it is important to see your optician regularly so that glaucoma can be diagnosed and treated before long-term visual loss occurs.
If you are over 40 and have a family history of glaucoma, you should have an eye examination at least every one to two years. If you have health problems such as diabetes or a family history of glaucoma or are at risk of other eye diseases, you may need to visit your optician more frequently.
Why does pressure rise in the eye to cause glaucoma?
Glaucoma usually occurs when intraocular pressure increases. This happens when the fluid pressure in the eye's anterior chamber, the area between the cornea and the iris, rises.
Normally, this fluid, called aqueous humour, flows out of the eye through a mesh-like channel. If this channel becomes blocked, fluid builds up, causing glaucoma. The direct cause of this blockage is unknown, but doctors do know that it is often inherited, meaning it is passed from parents to children.
Less common causes of glaucoma include a blunt or chemical injury to the eye, severe eye infection, blockage of blood vessels in the eye, inflammatory conditions of the eye, and occasionally eye surgery to correct another condition. Glaucoma usually occurs in both eyes, but it may involve each eye to a different extent.
What are the types of glaucoma?
The main types of glaucoma are:
Chronic open-angle glaucoma - the most common type of glaucoma which develops very slowly.
Primary angle-closure glaucoma - rare and can happen slowly in chronic cases or quickly in acute cases with a sudden and painful build-up of pressure in the eye.
Secondary glaucoma - resulting from an eye injury or a condition such as uveitis affecting the middle layer of the eye.
Developmental glaucoma or congenital glaucoma is rare and is either present at birth or develops shortly after birth due to an abnormality of the eye.
Normal-tension glaucoma (also called low-tension glaucoma) is a unique condition in which optic nerve damage and vision loss have occurred despite a normal pressure inside the eye.