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What is glaucoma?

Glaucoma is the name for a group of eye conditions which cause damage to the optic nerve at the back of the eye. When the optic nerve is damaged the visual information from your eyes cannot reach the brain (see how the human eye works), resulting in permanent sight loss.

People often talk about pressure in the eye when they discuss glaucoma, but glaucoma is not just about eye pressure. All eyes need a certain amount of pressure inside them to maintain the shape of the eye. In some types of glaucoma the pressure becomes abnormally high and it is thought that this pressure directly damages the optic nerve. However, in other types of glaucoma, the eye pressure is normal and it is thought that a weakness in the optic nerve leads to damage and visual loss.

Would I know if I had glaucoma?

In a small number of cases, glaucoma is associated with very high levels of eye pressure. Extreme eye pressure produces significant pain and redness of the eye. People often feel sick with the pain and report seeing haloes around lights at night. This type of glaucoma is a medical emergency and requires immediate treatment to reduce the eye pressure. Sometimes people will have episodes of raised eye pressure before a full blown attack and so it is important not to ignore symptoms of pain and redness in one eye, particularly if associated with haloes around lights. Most glaucoma however is not associated with very high eye pressure and therefore has no symptoms in the early stages of the disease.

How can glaucoma be detected?

Whenever you have an eye examination, the optometrist is always looking for signs of glaucoma. Having regular eye examinations should mean that glaucoma can be detected at an early stage before significant optic nerve damage has occurred.

Tests for glaucoma include

  • Measuring your level of vision

  • Measuring the eye pressure

  • Examining the optic nerve for signs of glaucoma damage

  • Examining the eye for signs that may predispose you to developing glaucoma

  • Measuring the visual field for signs of early vision loss

  • Optic nerve head 3D scans to help detect subtle changes over time

  • Measuring corneal thickness as thin corneas are associated with higher risk of glaucoma

The optometrist will look at the results of these tests and consider any other predisposing factors such as family history to judge whether you may be developing glaucoma. Your GP will not be able to tell you if you have glaucoma.

Can glaucoma be cured?

Glaucoma cannot be cured but it can be treated in an attempt to minimise the effect on vision. Glaucoma is usually treated by using eyedrops once or twice per day and this treatment must be continued indefinitely. In some cases glaucoma is treated by laser or surgery. For glaucoma to be successfully treated it is important that it is diagnosed at an early stage before significant loss of sight has occurred.

More useful information about glaucoma can be found at the following websites:


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