Glaucoma can occur for a number of reasons. Many cases are caused by a build-up of pressure in the eye.

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.

Glaucoma can occur if fluid is unable to drain from the eye properly, resulting in a build-up of fluid and pressure in the eye. This increase in pressure then damages the optic nerve (the nerve connecting the eye to the brain).

It's often unclear why this happens, although there are certain things that can increase the risk of it happening and in a few cases an underlying cause is identified.

Increased risk

Things that can increase your risk of developing glaucoma include:

  • age – glaucoma becomes more likely as you get older; the most common type (primary open angle glaucoma) affects up to 2 in 100 people over 40 and around 10 in 100 people over 75
  • ethnic origin – people of African, Afro-Caribbean or Asian origin are at increased risk of developing certain types of glaucoma
  • family history  if you have a close relative, such as a parent, brother or sister who has glaucoma, you're at increased risk of developing it yourself
  • other medical conditions  conditions such as short sightedness, long-sightedness and diabetes can increase your risk of glaucoma

Known causes

In a small number of cases, a cause for glaucoma is found.

Possible causes include:

  • a build-up of deposits in the drainage tubes in the eye – a common example is a condition called pseudoexfoliation glaucoma
  • new blood vessels growing inside the eye that block the drainage of fluid
  • uveitis (inflammation of the middle layer of the eye)
  • long-term use of steroid eye drops
  • eye injuries or previous eye surgery
  • a problem with the way the eyes developed – this can cause glaucoma in babies and young children

Page last reviewed: 16/09/2016

Next review due: 16/09/2019