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HealthInfo Canterbury

About glaucoma

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Glaucoma is caused by high eye pressure.

A healthy eye must have some pressure within it. Without any pressure it would collapse like a tyre with a puncture.

The eye has a pump that produces a small amount of fluid. If this fluid drains properly then the eye pressure (also called intraocular pressure) will be low, but if it isn't draining easily the eye pressure will rise. If the pressure gets too high, the optic nerve can be permanently damaged.

It is possible for your optic nerve to be damaged even if your eye pressure is normal.

Types of glaucoma

There are many different types of glaucoma, which can cause different symptoms and need different treatments.

Most people have open-angle glaucoma. In this type of glaucoma, fluid can't flow out of the eye properly, and the pressure gets too high. People with open-angle glaucoma have no symptoms until it is advanced, and then it causes loss of vision. The first signs you may notice are usually blind spots at the sides of your vision (peripheral vision loss) and in some cases reduced central vision. Glaucoma can lead to total blindness if you don't treat it.

Some people get acute angle-closure glaucoma, but this is less common. In this type of glaucoma the channels draining fluid from your eye become completely and suddenly blocked. This causes severe eye and brow pain, blurry or lost vision, redness in your eye, coloured haloes or rainbows around lights, and nausea or vomiting.


Acute angle-closure glaucoma is a medical emergency and must be treated immediately. This page has details of where to go for after-hours medical help.

The other types of glaucoma include low-tension, angle-recession, steroid-induced, pigmentary and neovascular glaucoma. Occasionally babies are born with glaucoma.

How is glaucoma diagnosed?

Glaucoma is diagnosed by testing your vision, including peripheral vision (visual field tests), looking through your pupil directly at the optic nerve, and by measuring the eye's pressure (intra-ocular pressure).

A good first step is to see an optometrist for these tests. You can also see a GP, but they may advise you to see an optometrist who can do more detailed tests. If your optometrist or GP thinks you may have glaucoma they will refer you to an ophthalmologist (eye doctor) who can confirm the diagnosis and start treatments.

On the next page: How do I know if I have glaucoma?

Compiled by Canterbury optometrists. Adapted by HealthInfo clinical advisers. Approved by clinical director, Ophthalmology, Canterbury DHB. March 2015.


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