There are several different types of glaucoma, which can have different symptoms, causes and treatments.
The main types include:
Primary open angle glaucoma, sometimes called chronic open angle glaucoma, is the most common type.
In this type of glaucoma, the part of the eye where fluid drains away (called the "angle") isn't blocked, but the fluid doesn't drain properly. This leads to increased pressure in the eye.
The condition usually develops very slowly over many years and doesn't cause any noticeable symptoms at first.
People oftendon't realise they have it because the outer areas of vision (peripheral vision) are affected first. Without treatment, vision towards the centre of the eye may also be lost.
Primary open angle glaucoma is usually picked up during a routine eye test, which you should have at least every two years. Visit an opticians or your GP if you're worried about any changes in your vision.
Primary angle closure glaucoma is a less common type that occurs when the part of the eye that drains fluid becomes blocked, causing pressure to build up in the eye.
Itoccasionally developsslowly over time, but often it causes sudden, severe symptoms.
Symptoms can include:
Sometimes these symptomsmay last for a few hours before disappearing.
If you experience sudden symptoms, go to your nearest eye casualty unit or accident and emergency (A&E) department as soon as possible. This is a medical emergency that may require immediate treatment.
Secondary glaucoma is an uncommon type of glaucoma caused by another eye problem.
Causes include uveitis (inflammation of the middle layer of the eye), eye injuries and certain treatments, such as medication or operations.
The symptoms can vary considerably, and may include:
Visit an opticians or your GP if you're worried about any changes in your vision.Go to your nearest eye casualty unit or accident and emergency (A&E) department as soon as possible if you have severesymptoms that occurred suddenly.
Childhood glaucoma, also called congenital or developmental glaucoma, is a type of glaucoma that affects babies and young children.
It's usuallythe result ofa problem in the development of the eyes, which causes fluid and pressure to build up inside them.
Spotting thecondition can be difficult, but your child may have some of the following symptoms:
Visit an opticiansor your GP if you notice any of these symptoms in your child.
Find out about glaucoma, including what it is, what the symptoms are, why it happens and how it's treated.
Find out about the main types of glaucoma, including open angle glaucoma and angle closure glaucoma.
Find out why glaucoma happens, including what can increase your risk of developing the condition.
Find out where to get tested for glaucoma and what tests may be carried out to diagnose the condition.
Find out about the main treatments for glaucoma, including eye drops, laser treatment and surgery.
Read about Linda Moore, who has had open angular glaucoma since she was 39.She runs the Poole Glaucoma Support Group, which supports people with glaucoma.