Some anatomy of your eye
When you look at an object, light from the object passes through the cornea of your eye, then the lens, and then it 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.
Your pupil (the black area in the middle of the eye) helps to regulate the amount of light that gets into your eye. The muscles of your iris (which gives colour to your eye) control the size of your pupil. Iris muscles can cause your pupil to dilate (enlarge) or constrict (get smaller). When your pupil is dilated, more light can get into your eye; when it is constricted, less light can get in.
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 substance a bit like jelly called the vitreous humour (humour meaning fluid). The front of your eye is filled with a clear fluid called aqueous humour, which is more watery. The part of your eye behind the lens that is filled with vitreous humour is called the posterior chamber. The part of the eye in front of the lens, that is filled with aqueous humour, is called the anterior chamber.
The aqueous humour is made continuously by the cells of the ciliary body. The aqueous humour fluid passes through your pupil to the front part of your eye, and then drains away through a sieve-like area called the trabecular meshwork located near the base of your iris. So, there is constant production and drainage of aqueous humour fluid. This keeps the fluid levels balanced.
What is acute angle-closure glaucoma?
Acute angle-closure glaucoma (AACG) occurs when the pressure inside your eye gets too high very quickly. It is an eye emergency because if it is not treated quickly, it can lead to permanent loss of vision. AACG is sometimes referred to as acute closed angle glaucoma or 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). A separate leaflet called ‘Glaucoma (Chronic Open Angle)’ gives further details. Other, less common types of glaucoma are secondary glaucoma and congenital glaucoma. The rest of this leaflet deals only with AACG.
What causes acute angle-closure glaucoma?
In AACG, there is a sudden blockage around the trabecular meshwork so that aqueous humour fluid cannot drain out of your eye. But more fluid is still being made, so the pressure inside your eye starts to rise quickly. As the pressure rises, this can start to damage the optic nerve at the back of your eye and your vision can be affected.
What causes the blockage?
Some people are more prone to develop AACG because of the anatomy (structure) of their eye. For example, if the area near the base of the iris is very narrow, the trabecular meshwork can get blocked more easily. Or, if the lens is thicker and sits further forward than normal, this can have the same effect. So, some people have what is known as a narrow drainage angle or a shallow anterior chamber. This can make you more likely to develop acute glaucoma. In some people, the iris can be thinner and more floppy than usual making it more likely to cause blockage of the trabecular meshwork.
As mentioned above, the iris muscles are responsible for controlling the size of your pupil. Commonly, in someone who is prone to AACG, it occurs when their pupil dilates (gets bigger) and their lens ‘sticks’ to the back of their iris. This means that the aqueous humour is not able to flow from the posterior chamber of their eye through the pupil to the anterior chamber. This block in the flow of fluid causes the pressure in the posterior chamber to rise. The aqueous fluid collects behind the iris and causes the iris to bulge forwards and block the trabecular meshwork. This prevents drainage of the aqueous fluid from their eye and the pressure within their eye rises rapidly. This is particularly likely to happen if you have a thin, floppy iris or a shallow anterior chamber.
Can anything trigger acute angle-closure glaucoma?
If you are prone to AACG there are some situations that may trigger it. For example, it is quite common that an attack of AACG comes on when you are in a situation where your pupil is likely to be more dilated. This could be whilst watching television in dim light or during a moment of stress or excitement.
Various medicines can also trigger AACG in people prone to it. However, for the population as a whole, the chance of getting acute glaucoma with these medicines is very small – so they are commonly prescribed without too much worry. But, if you have been warned that you may be prone to AACG, 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:
- Eye drops used to dilate (enlarge) the pupil – these may be used for eye checkups.
- Antidepressants of the tricyclic or SSRI types.
- Some of the medicines used to treat nausea, vomiting or schizophrenia (a type called phenothiazines).
- Ipratropium (used for asthma).
- Some medicines used to treat allergies or stomach ulcers, such as chlorphenamine, cimetidine and ranitidine.
- Medication used during a general anaesthetic.
Who gets acute angle-closure glaucoma?
About 1 in 1,000 people get AACG. It is more likely in people over the age of 40 years, and most often happens at around age 60 to 70 years. It is more common in long-sighted people and in women. It is also more common in Southeast Asian and Eskimo 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 eye shape is often inherited. So, if the anatomy of your relative’s eye has made them prone to developing AACG, it could be the same case for you. You should go for a checkup with an optometrist.
What are the symptoms of acute angle-closure glaucoma?
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 haloes (circles) seen around lights.
- The pain may spread around your head and be felt as a severe headache.
- Some people develop nausea (feeling sick), vomiting, or abdominal pain.
- Your eye might feel hard and tender.
As explained above, symptoms may begin in a situation of dim lighting, sudden excitement, after taking certain medicines, or after a general anaesthetic.
In some people, an attack of AACG can last for a few hours and then symptoms can improve again. However, attacks will usually recur. Each time that you have an 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.
How is acute angle-closure glaucoma diagnosed?
The diagnosis is made from the symptoms and the appearance of your eye. A provisional diagnosis may be made by any doctor (not necessarily an eye specialist). The diagnosis can be confirmed by an examination done by an eye specialist. This usually involves examining your eye using a special light and magnifier called a slit lamp and measuring the pressure in your eye. A special lens can also be used to examine the outflow channels around the trabecular meshwork area of your eye. This is called gonioscopy.
What is the treatment for acute angle-closure glaucoma?
Quick treatment is needed for AACG. You should be seen by an ophthalmologist (eye specialist) 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.
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 betablocker medication (to reduce fluid in your eye) and steroids (to reduce inflammation).
- An injection of a medicine called acetazolamide.
- Pilocarpine eye drops which can cause your pupil to 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 which can reduce fluid in your eye, such as brimonidine.
- Other fluid-reducing medication such as mannitol which is given intravenously (into a vein).
You may also be given painkillers and antisickness medication if needed.
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. Usually two small holes are made in your iris using a laser. The holes are almost unnoticeable to other people.
- 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. Sometimes eye drops are needed as long-term treatment to help keep your eye pressure under control.
What is the outlook for acute angle-closure glaucoma?
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.
Driving and glaucoma
Many people will be allowed to drive after recovering from 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, the law says that you must inform the Driver and Vehicle Licensing Authority (DVLA). The DVLA will usually contact your eye specialist and ask them for a report about your eye problems. The DVLA may also arrange an examination of your eyesight with an optician.
Can acute angle-closure glaucoma be prevented?
As mentioned above, some people have an increased risk of getting AACG because they have a shallow anterior chamber or narrow drainage angle. Sometimes, this can be 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 treatment such as laser iridotomy (see above) to prevent it.
Be aware of the symptoms of AACG. If you develop a red eye with pain or vomiting, or a red eye with reduced vision, you should seek medical advice immediately. If you take a new medication or have eye drops to dilate your pupil, and then have symptoms of AACG, seek medical advice straight away. Tell your doctor about the medication and symptoms. This makes it easier for the problem to be recognised early.
Further information and help
International Glaucoma Association
Woodcote House, 15A Highpoint Business Village, Henwood, Ashford, Kent TN24 8DH
Tel: 01233 648170
Royal National Institute of Blind People (RNIB)
105 Judd Street, London WC1H 9NE
Tel (helpline): 0303 123 9999 Tel (admin): 020 7388 1266
The UK’s leading charity offering information, support and advice to people with sight loss.
References and Disclaimer | Provide feedback
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- Gordon-Bennett P, Ung T, Stephenson C, et al; Misdiagnosis of angle closure glaucoma. BMJ. 2006 Dec 2;333(7579):1157-8.
- Noecker RJ, Kahook MY; Glaucoma, Angle Closure, Acute, eMedicine, Jun 2009