Acute Angle-closure Glaucoma

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Acute angle-closure glaucoma occurs when the fluid pressure inside your eye rises quickly. The usual symptoms are sudden, severe eye pain, a red eye and reduced or blurred vision. You may feel sick or be sick (vomit). Immediate treatment is needed to relieve symptoms and to prevent permanent loss of vision (severe sight impairment).


When you look at an object, light from the object passes first through the cornea of your eye, then the lens and then hits the retina at the back of your eye. The cornea and the lens both help to focus the light on to your retina. Nerve messages pass from the 'seeing cells' (rods and cones) in your retina, down nerve fibres in your optic nerve to your brain. The messages are interpreted by your brain, which enables you to see.

The black area in the middle of the eye (the pupil) helps to regulate the amount of light that gets into the eye. It does this by becoming smaller (constricted) when the light is brighter and larger (dilated) in dark conditions. The muscles of your iris (which gives colour to your eye) control the size of your pupil. 

Your eye also needs to keep its shape so that it can work properly and so that light rays are focused accurately on to the retina. So, most of your eye is filled with a clear jelly-like substance called the vitreous humour (humour meaning fluid). The front of your eye is filled with a clear watery fluid called aqueous humour.

The part of your eye behind the lens is called the posterior chamber and is filled with vitreous humour. The part of the eye in front of the lens is called the anterior chamber and is filled with aqueous humour.

Aqueous humour is made continuously by the cells of the ciliary body (which is at the back of the iris at its base). It passes through the pupil from the posterior chamber to the anterior chamber. From there it drains away through a sieve-like area called the trabecular meshwork (which is in front ot the iris, also near its base.) So, there is constant production and drainage of aqueous humour fluid. This keeps the fluid levels balanced.

AACG occurs when the flow of aqueous humour out of the eye is blocked and pressure inside the eye becomes too high very quickly. It is an emergency because if it is not treated quickly, it can lead to permanent loss of vision. AACG is also sometimes referred to as acute closed-angle glaucoma or just acute glaucoma.

There are other types of glaucoma which occur more gradually. The most common type is chronic open-angle glaucoma (also called primary open-angle glaucoma or simply chronic glaucoma). See separate leaflet called Chronic Open-angle Glaucoma for details.

Other, less common types of glaucoma are secondary glaucoma and congenital glaucoma. 'Congenital' means that it is present from birth. The rest of this leaflet deals only with AACG.

In AACG, there is a sudden blockage of drainage of aqueous humour fluid out of your eye. As more fluid continues to be made, the pressure inside your eye rises quickly. This can start to damage the optic nerve at the back of the eye and vision can be affected.

What causes the blockage?

Some people are more prone to develop AACG because of the structure (anatomy) of their eye. For example, if the area near the base of the iris is very narrow, the trabecular meshwork can become blocked more easily. If the lens is thicker and sits further forward than normal, this can have the same effect. Both these cause what is known as a narrow drainage angle or a shallow anterior chamber and can make acute glaucoma more likely. In other people, the iris can be thinner and more floppy than usual making it more likely to cause blockage of the trabecular meshwork.

The muscles of the iris control the size of your pupil. In someone who is prone to AACG the dilation of the pupil can mean their lens can 'stick' to the back of their iris. This blocks the route of the aqueous humour through the iris from the posterior chamber or through the pupil to the anterior chamber. The aqueous fluid collects behind the iris and causes the iris to bulge forwards and block the trabecular meshwork. This further prevents drainage of the aqueous fluid from their eye. The pressure within the eye rises rapidly. It is particularly likely to happen in people with a thinner, floppier iris or a shallow anterior chamber.

Can anything trigger AACG?

In people who are prone to AACG there are some situations that may trigger it. For example, AACG is more likely to come on when the pupil is dilated. This could be whilst watching television in dim light when the light from the screen flares, or during stress or excitement.

Some medicines can also trigger AACG in people prone to it, as can general anaesthetics in older people. For the population as a whole the chance of getting acute glaucoma with these medicines is extremely small, so they are commonly prescribed without serious concern. However, if you have been warned that you may be prone to AACG, you should tell your doctor before starting new medication or eye drops, especially if it is one on the list below.

Commonly used medicines which may trigger AACG are:

About 1 in 1,000 people develop AACG. It is more likely in people over the age of 40 years and most often happens at around age 60-70 years. It is more common in long-sighted people and in women. It is also more common in Southeast Asian and Inuit people.

If one of your close relatives (mother, father, sister or brother) has had AACG, you have an increased risk of developing it. This is because you may have inherited an eye shape which makes AACG more likely. If you have a positive family history like this you should speak to an optician regarding when, and how often, you should have eye checks.

The symptoms usually start suddenly. They include:

  • Sudden, severe pain within your eye and an ache around your eye.
  • Redness of your eye.
  • Blurred or reduced vision, often with circles (haloes) seen around lights.
  • The pain may spread around your head and be felt as a severe headache.
  • Some people develop a feeling of sickness (nausea) and are sick (vomit).
  • Your eye usually feels hard and tender.
  • You may feel generally unwell.
  • The clear surface of your eye (your cornea) can look hazy.

Symptoms may begin in a situation of dim lighting, sudden excitement, after taking certain medicines or after a general anaesthetic.

The symptoms usually continue to worsen unless treated and you should seek help immediately. Either an optician or an eye specialist (ophthalmologist) can make the diagnosis. 

Some people have milder symptoms, sometimes with intermittent attacks of blurring and haloes without pain. The attack may end when they go into a brighter room or go to sleep. Both of these cause the pupil to constrict and pull the iris away from the drainage channels. This is called intermittent ACG. The attack of AACG can last for a few hours and then symptoms can improve again. However, attacks will usually happen again and, with each attack, your vision may be damaged further. If you have these symptoms you should see a doctor urgently, in case you need treatment to prevent a more severe attack.

The diagnosis is made from the symptoms and the appearance of your eye. A likely diagnosis may be made by your GP, by an emergency doctor or by an optician. The diagnosis is confirmed by an examination done by an eye specialist (ophthalmologist). This usually involves examining your eye using a special light and magnifier called a slit lamp and measuring the pressure in your eye. A specialist can also use a gonioscope to directly examine the outflow channels around the trabecular meshwork area of your eye. 

Initial treatment

Quick treatment is needed for AACG. You should be seen by an eye specialist (ophthalmologist) as soon as possible. If it will take time getting to the ophthalmologist, some treatment can be started.

You should not try to cover the affected eye with a patch or a blindfold. If you do this, your pupil will dilate further and this can worsen the situation. Don't lie down in a darkened room - lying down can tend to raise the pressure in your eye still further. A darkened room will further dilate the pupil, making things worse.

The first treatment is medication to lower the pressure within your eye. There are various types of medicine and eye drops that may be used in different combinations. Treatments may include:

  • Eye drops containing beta-blocker medication (to reduce fluid production in your eye) and steroids (to reduce inflammation) - for example, timolol
  • An injection of a medicine called acetazolamide.
  • Pilocarpine eye drops which can cause your pupil to become smaller (constrict) and help to move the iris away from the trabecular meshwork. This helps to open up the obstruction to the flow of aqueous humour fluid.
  • Other types of eye drops are also used, including steroid eye drops.
  • Other fluid-reducing medication such as mannitol which is given into a vein (intravenously).

You may also be given painkillers and antisickness medication if needed.

Further treatment

When the pressure in your eye has gone down, further treatment is needed to prevent AACG from coming back. This involves using laser treatment or surgery to make a small hole in your iris. The hole allows fluid to flow freely around your iris and can stop the iris bulging forwards and blocking the trabecular meshwork in the future.

  • Laser treatment is called peripheral iridotomy. This is the usual treatment. Two (usually) small holes are made in your iris, using a laser. The holes are almost unnoticeable to other people. Laser treatment is done using local anaesthetic in an outpatient clinic.
  • Surgical treatment called surgical iridectomy is another option. A small, triangular hole is made in your iris. The hole is visible afterwards as a very small, black triangle at the edge of your iris.

Usually, laser or surgical treatment will be advised for the other eye, often at the same time. This is to prevent AACG in the other eye, which is otherwise quite likely. Sometimes eye drops are needed longer-term to help keep your eye pressure under control.

The outlook is good if treatment is started quickly. Your eye can recover and laser treatment or surgery can prevent the problem coming back. If the attack is severe, or if treatment is delayed, the high pressure in your eye can damage the optic nerve and blood vessels. If this is the case, there is a risk that your vision will be permanently reduced in the affected eye.

Many people will be allowed to drive after recovering from acute angle-closure glaucoma (AACG). Even if vision is reduced in one eye, you may still be allowed to drive if your vision is good enough in the other eye. However, you will need advice from your eye specialist. If you are a driver and have glaucoma causing loss of vision in both eyes, you must by law inform the Driver and Vehicle Licensing Authority (DVLA). The DVLA will usually contact your eye specialist (ophthalmologist) and ask them for a report about your eye problems. They may also arrange an examination of your eyesight with an optician.

As mentioned above, some people have an increased risk of developing AACG because they have a shallow anterior chamber or narrow drainage angle. Sometimes this is noticed at a routine eye examination. You may be told about this and advised to be careful with certain medicines and eye drops (see above). If you are at very high risk of AACG, you may be advised to have preventative treatment such as laser iridotomy (see above).

Be aware of the symptoms of AACG. You should seek medical advice immediately if you develop a red eye with any of the following:

  • Pain
  • Being sick (vomiting)
  • Reduced vision

If you take a new medication or have eye drops to enlarge (dilate) your pupil and then you develop symptoms of AACG, seek medical advice straightaway. Tell your doctor about the medication and symptoms. This makes it easier for the problem to be recognised early.

Original Author:
Dr Naomi Hartree
Current Version:
Peer Reviewer:
Dr Colin Tidy
Document ID:
9002 (v4)
Last Checked:
Next Review:
The Information Standard - certified member
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