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 Chronic Open Angle Glaucoma gives further 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.
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 structure (anatomy) 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 gets bigger (dilates) 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 the pupil – these may be used for eye check-ups.
- Antidepressants of the tricyclic or SSRI types.
- Some of the medicines used to treat feeling sick (nausea), being sick (vomiting) or the mental health condition called schizophrenia. (There is a type of medicine called phenothiazines, one of which is chlorpromazine.)
- 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 check-up with an optician.
What are the acute angle-closure glaucoma symptoms?
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), are sick (vomit) or develop tummy (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.
For most people the symptoms continue to get worse unless treated. You should seek help immediately. An optician can make the diagnosis as well as an eye specialist. The optician can refer directly to an eye specialist for treatment.
Some people have milder symptoms. An attack of AACG can last for a few hours and then symptoms can improve again. However, attacks will usually happen again (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.
Treatment of angle-closure glaucoma usually involves either laser or conventional surgery to remove a small portion of the bunched-up outer edge of the iris. Surgery helps unblock the drainage canals so that the extra fluid can drain.
If you have angle-closure glaucoma in one eye, doctors may go ahead and treat the other eye as a safety measure.
In general, surgery for angle-closure glaucoma is successful and long lasting. Regular checkups are still important though, because a chronic form of glaucoma could still occur.
- Systemic medicines (carbonic anhydrase inhibitors)
- As the pressure is very high inside the eye, this needs to be dropped rapidly and therefore medicines, such as acetazolamide, are given rapidly into the circulation through a vein. This should reduce the pressure quite quickly.
- Laser treatment
- A hole in the coloured part of the iris is essential in order to prevent this condition happening again. This hole is usually made using a laser.
- Both eyes need to be treated, as although only one eye is usually affected, the other eye will go on to develop acute closed angle closure if left untreated.
- Surgical treatment
- Sometimes all the above treatments do not allow control of the pressure and therefore a trabeculectomy (as outlined above in primary open angle glaucoma) may be required.
How is acute angle-closure glaucoma diagnosed?
The diagnosis is made from the symptoms and the appearance of your eye. A first (provisional) diagnosis may be made by any doctor (not necessarily an eye specialist) or by an optician. 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.
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 straightaway. Tell your doctor about the medication and symptoms. This makes it easier for the problem to be recognised early.