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Page last reviewed: 13/07/2011

Glaucoma is a term that describes a group of eye conditions that affect vision. Glaucoma often affects both eyes, usually in varying degrees. One eye may develop glaucoma quicker than the other.

If left untreated, glaucoma can cause blindness. But if it is diagnosed and treated early enough, further damage to vision can be prevented

Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked. This prevents eye fluid (aqueous humour) from draining properly.

When the fluid cannot drain properly, pressure builds up. This is called intraocular pressure. This can damage the optic nerve, which connects the eye to the brain, and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).

Types of glaucoma

There are four main types of glaucoma:

  • Chronic open-angle glaucoma: this is the most common type of glaucoma and develops very slowly.
  • Primary angle-closure glaucoma: this is rare and can occur slowly (chronic) or may develop rapidly (acute) with a sudden, painful build-up of pressure in the eye.
  • Secondary glaucoma: this occurs as a result of an eye injury or another eye condition, such as uveitis (inflammation of the middle layer of the eye).
  • Developmental glaucoma (congenital glaucoma): this is rare but can be serious. It is usually present at birth or develops shortly after birth. It is caused by an abnormality of the eye.

See the box (left) for more information about the terms used to describe the different types of glaucoma.

How common is glaucoma?

In Ireland, about 1,000 people have chronic open-angle glaucoma, with 85-90 new cases occurring each year. Among white Europeans, about 1 in 50 people above 40 years old and 1 in 10 people above 75 years old has chronic open-angle glaucoma. It may be more common among people of black-African or black-Caribbean origins.  

The other types of glaucoma are much less common. Among white people, acute angle-closure glaucoma may affect about 1 in 1,000 people. It is more common among people of Asian origin, affecting around 1 in 100 of them.


Glaucoma can be treated with eye drops, laser treatment or surgery (see Glaucoma - treatment). However, early diagnosis is important because any damage to the eyes cannot be reversed. Treatment aims to control the condition and minimise any future damage. 

Attending regular optician appointments will help to ensure that any signs of glaucoma can be detected early and allow treatment to begin. Without treatment, glaucoma can eventually cause blindness.

Glaucoma terminology

Different terms are used to describe glaucoma depending on the type of glaucoma.

Open-angle or angle-closure glaucoma

This refers to the angle between the iris (the coloured part of the eye) and the cornea (the transparent layer of tissue that covers the front of the eye). Within this angle are the tubes that allow the fluid in the eye to drain out. See the Causes page for an illustration.

  • An open angle is when the fluid can still reach the drainage tubes but they are slowly becoming blocked.
  • A closed angle (angle closure) is when the angle narrows so much that fluid cannot reach the drainage tubes.

Angle-closure glaucoma can be chronic or acute.

Chronic or acute glaucoma

Chronic means long-term. Acute means short-term. Chronic glaucoma is therefore glaucoma that develops slowly over a long period of time. Acute glaucoma develops very quickly over a short period of time.

Primary or secondary glaucoma

Primary glaucoma is the term used to describe the condition when it develops on its own (in practice, this may just be called ‘glaucoma’).

Secondary glaucoma is where glaucoma develops as the result of another condition. Secondary glaucoma can be open-angle or angle-closure.

Page last reviewed: 13/07/2011

The symptoms of the different types of glaucoma are explained below.

Chronic open-angle glaucoma

In cases of chronic glaucoma, there are usually no noticeable symptoms because the condition develops very slowly. People with this type of glaucoma often do not realise that their sight is being damaged. This is because the first part of the eye to be affected is the outer field of vision (peripheral vision). Vision is lost from the outer rim of the eye, slowly working inwards towards the centre.

Changes in vision are often linked to getting older, which is why it is so important to have your eyes checked regularly. You should have an eye test at least every two years, or more frequently if your optometrist (healthcare professional who tests sight) recommends it.

Acute angle-closure glaucoma

Due to the rapid development of acute glaucoma, the symptoms are often severe. They include:

  • intense pain
  • redness of the eye
  • headache
  • tender eye area
  • seeing halos or 'rainbow-like' rings around lights
  • misty vision
  • loss of vision in one or both eyes that progresses very quickly 

As a result of these symptoms, some people may also feel sick or be sick.

The symptoms of acute glaucoma are not constant. They can last for one or two hours before disappearing again. But each time the symptoms occur, your vision is damaged a little more.

It is important to contact your GP straight away if you have any of the above symptoms, because early treatment can prevent further damage occurring.

If you have symptoms outside your GP's normal working hours, visit your nearest accident and emergency (A&E) department. The healthcare professionals at A&E will relieve the pressure within your eye and treat any pain.

Secondary glaucoma

Secondary glaucoma is caused by other conditions or eye injuries, such as uveitis (inflammation of the middle layer of the eye). It is possible for the symptoms of glaucoma to be confused with the symptoms of the other condition. For example, uveitis often causes painful eyes and headaches. 

However, the glaucoma may still cause misty vision and rings or halos around lights.

Developmental glaucoma

Recognising the symptoms of developmental glaucoma (also known as congenital glaucoma) can be very difficult due to the young age of the baby or child.

However, your child may display symptoms, such as:

  • large eyes due to the pressure in the eyes causing them to expand
  • being sensitive to light (photophobia)
  • having a cloudy appearance to their eyes
  • having watery eyes
  • jerky movements of the eyes
  • having a squint, which is an eye condition that causes one of the eyes to turn inwards, outwards or upwards, while the other eye looks forward

If you notice any of these symptoms, visit your GP or optometrist as soon as possible.

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Page last reviewed: 13/07/2011

Glaucoma is caused by a blockage in part of the eye. This prevents fluid draining out of the eye, and increases pressure in the eye, called intraocular pressure.

How the eye works

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. It drains back into the bloodstream at the same rate that it is produced to maintain the correct pressure.

Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked, preventing the aqueous humour from draining properly. An obstruction within the eye, such as a blood vessel blocking the trabecular meshwork, can also prevent fluid from draining properly.

When the fluid cannot drain properly, the pressure in the eye builds up and can damage the optic nerve, which is the nerve that connects the eye to the brain, and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).

It is not known why the drainage tubes become blocked or why other parts of the eye obstruct the tubes.

Risk factors

There are various factors that can increase your risk of developing glaucoma. These are explained below.

  • Age: glaucoma becomes more likely as you get older. In the UK, chronic open-angle glaucoma affects 1 to 2 people in every 100 who are over 40 years old, and 4 to 5 people in every 100 who are over 80 years old. 
  • Ethnic origin: people of African or Afro-Caribbean origin are at increased risk of developing chronic open-angle glaucoma. People of Asian origin are at increased risk of developing acute angle-closure glaucoma.
  • Short sightedness (myopia): people who are short-sighted are more likely to develop chronic open-angle glaucoma.
  • Ocular hypertension (OHT - raised pressure in the eye): people with OHT are at increased risk of developing chronic open-angle glaucoma. Your optometrist will be able to diagnose OHT (see Glaucoma - diagnosis).
  • Family history: if you have a close relative, such as a parent, brother or sister who has glaucoma, you are at increased risk of developing the condition yourself. You should therefore have regular eye tests to monitor the condition of your eyes.
  • Medical history: people with diabetes, which is a condition caused by too much glucose in the blood, may be at increased risk of developing glaucoma.

Page last reviewed: 13/07/2011

If you have glaucoma, it can take a long time before you realise that you have a problem with your eyesight. This is because glaucoma usually damages the outer edge of the eye and works slowly inwards. You may not notice a problem until the glaucoma is near the centre of your eye.

It is therefore very important to have regular eye tests so that any problems can be detected and treated as early as possible.

You should have an eye test at least every two years or more frequently if advised by your optometrist (a healthcare professional who tests sight). For example, they may suggest that you have more frequent eye tests if you have a close blood relative with glaucoma, such as a parent, brother or sister.

Tests for glaucoma

There are several glaucoma tests that your optometrist can perform. They are painless and quite quick. The tests should be carried out during the same appointment to ensure that the results are as accurate as possible.

The tests that you may have for glaucoma are explained below.

Eye pressure test (tonometry)

An eye pressure test (tonometry) uses an instrument called a tonometer to measure the pressure inside your eye. A small amount of anaesthetic (painkilling medication) and dye is placed onto your cornea (the transparent layer of tissue that covers the front of the eye). A blue light from the head of the tonometer is held against your eye to measure the intraocular pressure.

Tonometry can diagnose ocular hypertension (OHT - raised pressure in the eye), which is a risk factor for chronic open-angle glaucoma. 

Central corneal thickness

The thickness of your cornea will be measured because this is thought to affect how the intraocular pressure is interpreted.


Gonioscopy is an examination of the front outer edge of your eye, between the cornea and the iris (the coloured part of your eye). This is the area where the fluid should drain out of your eye. A gonioscopy can help to determine whether this angle is open or closed (blocked).

Visual field test (perimetry)

A visual field test (perimetry) checks for missing areas of vision. You will be shown a sequence of light spots and asked which ones you can see. Some dots will appear in your peripheral vision (around the sides of your eyeball), which is where glaucoma begins.

If you cannot see the spots in your peripheral vision, it may indicate that the glaucoma has damaged your vision.

Optic nerve assessment

Your optic nerve connects your eye to your brain. Your optometrist will use eye drops to enlarge your pupils. They will then examine your eyes using a slit lamp (a microscope with a very bright light) and assess whether your optic nerve has been damaged by the glaucoma.

The eye drops that are used to widen your pupils could affect your ability to drive. Therefore you may need to make alternative arrangements for getting home after your appointment, such as asking a family member to collect you.


If your optometrists suspects that you have glaucoma, they will refer you to an ophthalmologist (see box, right) for further tests. Your ophthalmologist will confirm your diagnosis and find out:

  • how developed the glaucoma is
  • how much damage the glaucoma has done to your eyes
  • what may have caused the glaucoma

They will then be able to advise you about the treatment that you need (see Glaucoma - treatment).

In some cases, your ophthalmologist will continue to treat you. But if you have chronic open-angle glaucoma, you may be referred back to your optometrist who will continue your treatment. 

The cornea is the clear outer layer at the front of the eyeball that acts as a window to the eye.

The coloured part of your eye.

The ophthalmic team

  • An optometrist examines eyes, tests your sight and prescribes and provides glasses and contact lenses. Optometrists are trained to recognise defects in and eye diseases, and some prescribe treatment for common eye conditions.
  • An ophthalmic medical practitioner (OMP) is a medical doctor who specialises in eye care. They examine the eyes, test sight, diagnose abnormalities and prescribe corrective lenses.
  • An ophthalmologist is a medical doctor who specialises in eye disease and its treatment. They mainly work in hospitals and hospital eye departments.
  • A dispensing optician fits prescriptions for glasses provided by optometrists, OMPs or ophthalmologists. They may also fit contact lenses after having specialist training. A dispensing optician does not examine the eyes.
  • An orthoptist specialises in problems relating to the development of vision in children. They help to identify and treat squints, lazy eyes and double vision.
  • An ophthalmic nurse is a nurse who has skills in eye care. Ophthalmic nurses work in hospital eye departments.

Page last reviewed: 13/07/2011

Any damage to your vision that is caused by glaucoma cannot be repaired. This is why it is so important to get an early diagnosis so that the glaucoma can be treated and prevented from developing further.

The aim of treatment for every type of glaucoma is to reduce the pressure in the affected eye, called the intraocular pressure.

Eye drops for chronic open-angle glaucoma

Chronic open-angle glaucoma is often treated using eye drops. There are several different types of eye drops that may be prescribed. The choice of eye drops may depend on:

  • how your condition is progressing
  • whether you have any other medical conditions
  • whether you are currently taking any other medications
  • whether the eye drops cause any side effects when you use them

The different types of eye drops are described below.

Prostaglandin analogue

Prostaglandin analogues increase the flow of fluid (aqueous humour) out of your eye, which reduces the pressure within your eye (the intraocular pressure). These eye drops are usually used once a day. Side effects include:

  • enlarged blood vessels in the white part of your eye, making your eye look red
  • changes to your eye colour - it often gets darker
  • eyelashes growing thicker and darker
  • eye pain and irritation
  • blepharitis - a condition where the rims of your eyelids become red and swollen
  • dry eyes
  • headaches
  • sensitivity to light

Some types of prostaglandin analogues that you may be prescribed include:

  • latanoprost 
  • tafluprost
  • travoprost


It is thought that beta-blockers reduce intraocular pressure by slowing down the production of aqueous humour in your eye. They are used once or twice a day and can cause side effects such as:

  • a stinging or burning sensation in your eye
  • dry eyes
  • itchy eyes

Beta-blockers can make some medical conditions worse, so do not use them if you have:

See the Health A-Z topic about Beta-blockers for more information about this medicine, including their side effects and what medicines they interact with.

Some types of beta-blockers that you may be prescribed include:

  • betaxolol hydrochloride 
  • levobunolol hydrochloride 
  • metipranolol

Carbonic anhydrase inhibitors

Carbonic anhydrase inhibitors reduce the amount of aqueous humour produced in your eye, which reduces intraocular pressure. These drops are used two or three times a day and may cause:

  • a bitter taste in your mouth
  • nausea (feeling sick)
  • a dry mouth
  • eye irritation

Some types of carbonic anhydrase inhibitors that you may be prescribed include:

  • brinzolamide
  • dorzolamide


Sympathomimetics are thought to reduce the rate of production of aqueous humour and increase the flow of aqueous humour out of the eyes. These eye drops are used twice a day and may cause your eyes to become painful and red.

Some types of sympathomimetics can only be used with caution in people who have:

A type of sympathomimetic that you may be prescribed is brimonidine tartrate.

Other treatments for chronic open-angle glaucoma

If the use of eye drops does not improve your symptoms, a different type of treatment may be recommended, such as laser treatment or surgery. These are described in more detail below.

Laser treatment

Laser treatment, which uses high energy beams of light, can be used to open up the blocked trabecular meshwork (drainage tubes) within your eye. This is called laser trabeculoplasty.

Anaesthetic (painkilling) eye drops will be put into your eye and a special lens will be placed in front of your eye. The laser will be shone through the lens and will make small holes in the trabecular meshwork. This allows more fluid to drain out of your eye and reduces the intraocular pressure.

An alternative to laser trabeculoplasty is cyclodiode laser treatment. This involves destroying some of the tissue in the eye that produces aqueous humour. It creates less fluid in the eye, which reduces the intraocular pressure.

Laser treatments are usually quick and painless, although during the procedure you may feel a brief twinge of pain or heat. You may still need to use eye drops (see above) after having laser treatment.


A trabeculectomy is the most common type of glaucoma surgery. It involves removing part of the trabecular meshwork to allow fluid to flow through the eye's drainage system. The procedure will be carried out under local anaesthetic (you will still be conscious) or general anaesthetic (you will be unconscious).

Other types of surgery include:

  • a viscocanalostomy - this operation removes part of the sclera (the white outer covering of the eyeball), enabling the fluid to filter out of your eye and into your body
  • a deep sclerectomy operation - this operation involves implanting a tiny device inside your eye to widen the trabecular meshwork
  • an aqueous shunt implant - this operation involves placing a tube device into your eye to increase the drainage of fluid out of your eye

Speak to your surgeon to find out more about your procedure and the risks involved.

If you are having surgery, your surgeon may choose to use anti-scarring medicines. These can improve the success of the operation by preventing scar tissue forming as your eye heals. You may be prescribed:

  • mitomycin C or
  • 5-fluorouracil

These medications are unlicensed for the treatment of glaucoma. This means that the manufacturers of these medications have not applied for a licence for their medication to be used to treat glaucoma. In other words, the medications have not undergone clinical trials (research that tests one treatment against another) to see if they are effective and safe in treating glaucoma.

Many experts will use an unlicensed medication if they think the medication is likely to be effective and the benefits of treatment outweigh any associated risk. The National Institute for Health and Clinical Excellence (NICE) has issued guidance for the treatment of chronic open-angle glaucoma. It suggests that these medicines can be used.

If your ophthalmologist (medical doctor who specialises in eye disease) is considering prescribing an unlicensed medication, they should inform you that it is unlicensed, and discuss the possible risks and benefits with you.

Acute angle-closure glaucoma

As acute glaucoma develops rapidly, the condition needs to be treated quickly. The most common forms of treatment for this type of glaucoma include:

  • eye drops - see above for further details
  • systemic medicines - these are injected into your bloodstream to quickly reduce the pressure in your eye
  • laser treatment (called laser iridotomy) - this uses high-energy beams of light to create holes in your iris (coloured part of the eye) to open the angle and enable fluid to flow; both eyes may need to be treated, even if only one has acute angle-closure glaucoma, because this form of glaucoma may develop in both eyes at some point
  • surgery - a trabeculectomy (surgery to remove part of the drainage tubes) is the most common form of surgery for acute glaucoma

If you also have a cataract, which is a cloudy patch in the front of your eye, removing it may open the angle in your eye and control the intraocular pressure. See the Health A-Z topic about Cataract surgery for more information about this procedure.


Acute angle-closure glaucoma may also be treated with a medication called a miotic, such as pilocarpine. Miotics work by opening up the blocked trabecular meshwork, which should improve the drainage of aqueous humour out of your eye. You may need to use these eye drops up to four times a day.

Miotics should be used with caution in people who have certain medical conditions, including: 

Miotics can also cause some side effects, such as:

  • a headache, which may be severe during the first two to four weeks of treatment
  • burning or itchy eyes
  • blurred vision, which may affect your ability to drive

Treating other types of glaucoma

For other types of glaucoma, your specialist will usually recommend eye drops, laser treatment or surgery. Your treatment will depend on the type of glaucoma that you have and how advanced it is.

Aqueous humour
A watery substance inside your eyeball that creates pressure in the eye to give it shape. In healthy eyes, this fluid constantly flows in and out of the eye to maintain the correct pressure.
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Intraocular pressure
The pressure inside the eyeball.
Trabecular meshwork
The drainage tubes in the eyes that allow the aqueous humour to flow in and out.

Monitoring your condition

If you have been diagnosed with glaucoma, as well as the treatments explained here, your condition will be closely monitored to check for any further damage to your vision.

Depending on how your condition is progressing, you may need further appointments every 1 to 4 months or up to 12 to 24 months apart. These will either be with:  

  • an optometrist – a healthcare professional who examines eyes, tests vision and is trained to recognise eye diseases and vision defects
  • an ophthalmologist – a medical doctor who specialises in eye diseases and their treatment and surgery

Monitoring your condition is likely to involve some of the same tests that were used during your diagnosis. See Glaucoma - diagnosis for more information.

At these appointments you may be given eye drops that make your pupils larger. This could affect your ability to drive. Therefore, you may need to make alternative arrangements to get home after your appointment, such as asking a family member to collect you.

Using eye drops

If you have been prescribed eye drops to treat glaucoma, it is important that you use them as directed. Even if you have not yet noticed any problems with your vision, without treatment glaucoma can cause permanent vision loss.

To use eye drops:

  • use your finger to gently pull down your lower eyelid
  • hold the bottle over your eye and allow a single drop to fall into the pocket you have created in your lower lid
  • close your eye and keep it closed for several minutes

If you are using two different types of eye drops, allow at least 5 to 10 minutes between using the different types. You should also follow any other advice that your optometrist or ophthalmologist has given you.

Contact lenses

If you usually wear contact lenses and have been prescribed eye drops, you may need to stop wearing your lenses and wear glasses instead. This is because the medication in the eye drops can build up in the lenses and may harm your eyes. You should discuss this with the healthcare professionals treating you.

Page last reviewed: 13/07/2011

Loss of vision is the main complication of glaucoma. This is why early diagnosis and treatment is so important.

Loss of vision

Glaucoma is responsible for 1 in 10 cases of blindness. If you have some loss of vision due to glaucoma, more information is available on the National Council for the Blind website. They offer advice about living with sight loss and registering your sight loss - this may allow you to access certain benefits.

Complications from treatment

If you have surgery to treat glaucoma, there is always a risk of infection. Most infections can be treated with a course of antibiotics (medication to treat bacterial infections).

You may also have a reaction to certain types of eye drops. Speak to the healthcare professionals treating you if you feel unwell while you are being treated for glaucoma.


If you have glaucoma, it could affect your ability to drive.

It is important that you inform your doctor and the Road Safety Authority (RSA) about a medical condition that could have an impact on your driving ability.

See further information at http://www.rsa.ie/RSA/Licensed-Drivers/Safe-driving/Medical-Issues/

Page last reviewed: 13/07/2011

Regular eye tests are very important in helping to prevent glaucoma.

Your optometrist (a healthcare professional who tests sight and examines eyes) will usually talk you through each part of the eye test so that you know what they are testing for. When having a sight test, you should inform the optometrist if glaucoma runs in your family.

An ophthalmologist is a medical doctor who specialises in eye disease and its treatment or surgery. They mainly work in hospitals and hospital eye departments.
An optometrist (ophthalmic optician) examines eyes and tests sight. They can prescribe glasses and contact lenses, and are trained to recognise sight defects and eye diseases.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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