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Glaucoma is the name given to a group of eye conditions where there is damage to your optic nerve. This may be because your eye pressure is higher than normal, or because of a weakness in the structure of your optic nerve.

Your eye needs a certain amount of pressure to keep the eyeball healthy and in the right shape. But if the pressure is too high, it can cause your optic nerve to become damaged at the point where it leaves your eye. This damage is called glaucoma.

This page contains a summary of our information on glaucoma. To read our full information, download our understanding glaucoma booklet, which is accredited by the Royal College of Ophthalmologists:

What are the main types of glaucoma?

Primary glaucoma

These types of glaucoma occur without a known cause and aren’t caused by any other eye condition.

  • Primary open angle glaucoma where damage to the optic nerve occurs slowly over a long period of time due to your eye pressure increasing to more than 21mmHg. This is the most common form of glaucoma.
  • Normal tension glaucoma when an eye pressure of less than 21mmHg still causes damage to the optic nerve.
  • Primary closed angle glaucoma is caused when the angle, where the aqueous fluid drains from the eye, narrows or closes. It can be chronic (gradual onset) or acute (where damage to the optic nerve can happen very quickly due to a sudden rise in eye pressure).

Secondary glaucoma

Secondary glaucoma occurs as a result of another eye condition, an injury to the eye or due to medication.

Childhood glaucoma

Glaucoma which affects babies and children is rare. There are two main types of childhood glaucoma:

  • Primary congenital glaucoma which occurs when the aqueous drainage system hasn’t developed properly before birth.
  • Secondary glaucoma which is caused by another developmental anomaly of the eye, a syndrome or another eye condition.

Primary open angle glaucoma (POAG)

This is the most common type of glaucoma in the UK. It’s also known as chronic open angle glaucoma which means the damage to your optic nerve and changes to your sight happen very slowly over time.

Will I have any symptoms?

You can’t ‘feel’ primary open angle glaucoma; it doesn’t cause any symptoms and the eye pressure doesn’t cause any pain. You may not notice any difference in your vision because glaucoma affects your peripheral vision (side vision) first. As your peripheral vision is not as sensitive as your central vision, it’s difficult to notice any early changes to your vision, even though your sight is being damaged.

Because you may not notice a problem until your glaucoma is more advanced, it’s important to have regular eye examinations as this is the only way to know if you have it. The earlier your glaucoma is picked up and treated, the more your sight can be protected.

How can primary open angle glaucoma affect my sight?

If there is damage to your optic nerve, blind spots can begin to form in the outer edges of your vision. You may miss things in your peripheral vision, but often you will have no symptoms until the condition is advanced.

Without treatment, sight loss can slowly progress so that your field of vision becomes very narrow, your night vision becomes poor and it can appear as if you’re looking through a tunnel. Finally, if left untreated, your central vision may be affected too, causing blind spots to appear when you look straight ahead.

Unfortunately, once sight loss occurs, it can’t be reversed as there are currently no treatments which can restore the damaged nerve. This means that it’s important that your glaucoma is picked up and treated early to prevent optic nerve damage in the first place and to avoid sight loss.

What is the treatment for primary open angle glaucoma?

All treatment for glaucoma aims to lower your eye pressure to prevent damage to your optic nerve and your sight.

Treatment to lower your eye pressure usually starts with eye drops, and for most people with glaucoma, this is all the treatment they will ever need. These drops will need to be used long term or for life.

When you are first diagnosed with glaucoma, you may be offered laser treatment as your first treatment option. If you have already started on drops as treatment for your glaucoma, the ophthalmologist will only recommend laser treatment if the drops are not controlling your eye pressure properly.

In a very small number of people with glaucoma, where eye drops haven’t been successful in keeping the eye pressure stable, or where the glaucoma is advanced, surgery may be an option. The most common surgery for glaucoma is called a trabeculectomy.

Normal tension glaucoma

This type of glaucoma occurs when your eye pressure is within normal range but causes damage to your optic nerve.

It’s not entirely known why some people’s optic nerve becomes damaged even though their eye pressure is at a normal level. It’s thought that perhaps some people’s optic nerve may just be weaker or have a more fragile blood supply and be unable to cope with an eye pressure within the normal range.

Normal tension glaucoma is treated in the same way as open angle glaucoma – by lowering your eye pressure to a level which is right for you, to protect your sight.

Ocular hypertension (high eye pressure)

Some people naturally have eye pressure above the normal range, but this pressure doesn’t cause any damage to their optic nerve. This is described as ocular hypertension rather than glaucoma.

Different people can have different optic nerve strengths, and some people’s optic nerves stay healthy at higher than normal eye pressures.

If you have ocular hypertension, it can increase your risk of developing glaucoma, so this needs to be monitored. Sometimes you may be prescribed eye drops or offered laser treatment to help reduce your eye pressure and reduce your risk of developing glaucoma. If this is the case, you’ll be followed up at the eye clinic regularly to monitor your eye pressure. You may be discharged from the eye clinic if you don’t require eye drops and tests show that there is no sign of glaucoma. However, it’s important for you to visit your optometrist (optician) regularly for your eyes to be checked so that any future changes can be picked up.

Managing your glaucoma

Having glaucoma may mean you need to make a few changes to your everyday life to prevent sight loss. For many people, this includes using eye drops daily and for most people having to attend regular eye clinic visits.

The most important thing you can do to protect your sight is to keep to the treatment that has been recommended for you. For many people with glaucoma, this involves putting in eye drops daily. It may help to make putting in your drops part of your daily routine, such as brushing your teeth, so that you don’t forget. It’s important to remember to use your drops regularly as prescribed, to prevent glaucoma from getting worse and causing damage to your sight.

It’s also very important to attend all your appointments at the eye clinic to make sure your eye pressure stays stable. This is because changes in eye pressure have no symptoms, and without regular checks you won’t be able to tell that your treatment is working. It also gives you a good opportunity to ask your ophthalmologist any questions you may have about your glaucoma treatment. How often you need to be seen at the eye clinic will depend on how well your treatment is working.


It’s completely natural to be upset when you’ve been diagnosed with glaucoma and it’s normal to find yourself worrying about the future and how you will manage with a change in your vision. We’re here to support you every step of the way, and to answer any questions you may have – just get in touch with our Sight Loss Advice Service.

Help to see things better

If glaucoma is picked up and treated early, you may not experience much of a change to your vision. You can carry on with everyday activities such as reading, watching television, and using the computer – these things will not make your glaucoma worse.

If you do have some sight loss, a low vision assessment can explore how to make the most of your sight. This may mean making things bigger, using brighter lighting, or using colour to make things easier to see. Your GP, optometrist or ophthalmologist can refer you to your local low vision service for an assessment. You can also find out tips for making the most of your sight by downloading our booklet:

Useful contacts

Glaucoma UK is a charity providing help, information and support to people affected by glaucoma.

Page last reviewed: May 18, 2023

Next review due: May 21, 2026