Glaucoma - Causes of glaucoma
- Introduction
- Symptoms of glaucoma
- Causes of glaucoma
- Diagnosing glaucoma
- Treating glaucoma
- Complications with glaucoma
- "If I'd not gone for regular eye tests I might not be able to see now"
- 'I know of people whose eyesight got worse almost overnight'
- prevention
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.
Increased risk
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
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