Acute Glaucoma

What is acute glaucoma?

Acute glaucoma occurs when the pressure inside the eye gets high very quickly.

Note: acute glaucoma is also called 'acute angle closure glaucoma' or 'acute closed angle glaucoma'. Another term sometimes used is 'primary angle closure glaucoma', which is a similar situation that can lead to acute glaucoma.

There are other types of glaucoma, which occur more gradually. The most common type is 'primary open angle glaucoma' (also called 'chronic glaucoma'). See separate leaflet on 'Glaucoma (Primary Open Angle'). Other, less common types are 'secondary glaucoma' and 'congenital glaucoma'. The rest of this leaflet deals only with acute glaucoma.

What causes acute glaucoma?

What happens in acute angle glaucoma?

In acute glaucoma, there is a sudden blockage, so that aqueous fluid cannot drain out of the eye. This happens if the iris (the coloured part of the eye) gets too close to the lens. Fluid gets stuck behind the iris and makes it bulge forwards. This bulging then blocks the drainage area (the trabecular meshwork), so that fluid cannot leave the eye. But more fluid is still being made, so the pressure inside the eye starts to rise quickly.

What causes the blockage?

Usually it is a combination of factors. In some people, the area near the base of the iris is very narrow, so it more easily gets blocked. In other people, the lens of the eye may be swollen, which has the same effect. This situation is called a 'narrow drainage angle' or 'shallow anterior chamber' and makes a person more susceptible to acute glaucoma.

The iris (the coloured part of the eye) is also involved. The iris muscle is responsible for controlling the size of the pupil (the black area in the middle of the eye). When the iris muscles enlarge the pupil, they tend to bulge, which can block the flow of fluid if the area is already narrow. The pupil enlarges in conditions of dim light, sudden excitement, or with certain medications. For this reason, acute glaucoma is more likely to occur in the evening, or in situations like watching a football match on TV (dim lighting and sudden excitement).

What can trigger acute glaucoma?

Various medications can trigger acute glaucoma if you are susceptible 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 susceptible to acute glaucoma, tell your doctor before starting new medication or eye drops, especially if it is one of the ones listed below.

Commonly used medicines which may trigger acute glaucoma are:

• Eye drops used to dilate (enlarge) the pupil - they 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).
• Topiramate.
• Some medicines used to treat allergies or stomach ulcers, such as chlorpheniramine, cimetidine and ranitidine.
• Medication used during a general anaesthetic.

Lying on your front (for a long period) may also affect fluids in the eye, and can trigger acute glaucoma. This can occur, for example, during an operation on the spine.

Who gets acute glaucoma?

Approximately 1 in 1000 people get acute glaucoma. It is more likely in people over age 40 years, and most often happens at around age 60-70 years. It is more common in long-sighted people and women. It is also more common in certain populations: Southeast Asian and Eskimo people.

What are the symptoms of acute glaucoma?

The symptoms usually start suddenly. They are:

• Sudden, severe pain in the eye.
• Redness of the eye.
• Reduced vision, often with 'haloes' (circles) seen around lights.
• The pain may be spread around the head and be felt as a severe headache.
• Sometimes, the pain may cause nausea, vomiting, or there may be abdominal pain (tummy pain) as well.
• Some people may not get eye pain, but instead have some of the other symptoms listed here, such as headache or abdominal pain with a red eye or reduced vision.
• The pupil (black part of the eye) will look large, and the clear part of the eye looks hazy ('milky' or 'steamy').

As explained above, symptoms often begin in a situation of dim lighting, sudden excitement, with certain medications or after a general anaesthetic.

Are there any warning symptoms?

Acute glaucoma can start 'out of the blue' with no warning. However, you may have warning symptoms, which often are not recognised. These occur when pressure rises in the eye, and then improves by itself. The symptoms are: blurred vision, seeing haloes or rainbows around lights, and eye pain. The warning symptoms can come and go - they may start in the evening (with dim light), and may settle after sleep (because sleep relaxes the iris muscles).

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 glaucoma diagnosed?

The diagnosis is made from the symptoms and the appearance of the eye. A provisional diagnosis can 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 measuring the pressure in the eye (a quick and easy test) and examining the eye using a special light and magnifier called a 'slit lamp'.

What is the treatment for acute glaucoma?

Initial treatment

Treatment is very urgent. You should be seen by an ophthalmologist (eye specialist) immediately. If it will take time getting to the ophthalmologist, treatment can be started meanwhile.

The first treatment is medication to lower the pressure of fluid in the eye. There are various types of medicine that reduce eye pressure. Different combinations can be used, depending on your medical history. The usual treatment is:

• An intravenous injection of acetazolamide.
• Eye drops containing beta-blocker medication (to reduce fluid in the eye) and steroid (to reduce inflammation).

Other treatments which may be used initially are:

• Painkillers and anti-sickness medication, if needed.
• Usually, it is recommended that you lie flat on your back - this position may help drain the trapped fluid.
• Other types of eye drops which reduce fluid in the eye, such as brinzolamide, brimonidine or pilocarpine.
• Other fluid-reducing medication such as intravenous mannitol.

Further treatment

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

Laser treatment is called 'peripheral iridotomy'. This is the usual treatment, and the preferred option, as it does not involve surgery to the eye. Two small holes are made in the iris using a laser. The holes are almost unnoticeable to other people.

Surgical treatment is called surgical iridectomy. It makes a small, triangular hole in the iris. The hole is visible afterwards as a very small, black triangle at the edge of the iris.

Sometimes, another type of surgery is used, which is similar to a cataract operation. This operation removes the lens of the eye - which can help if a swollen lens was causing the acute glaucoma in the first place. As with cataract operations, the lens which is removed can be replaced by an artificial lens, or by using glasses.

Usually, laser or surgical treatment will be advised for the other eye at some stage. This is to prevent acute glaucoma happening in the other eye. Also, eye drops may sometimes be needed as long-term treatment, to help keep the eye pressure under control.

What are the complications of acute glaucoma?

If treatment is delayed, the high pressure in the eye can damage nerves and blood vessels. This can cause reduced vision, and in severe cases can cause blindness in the affected eye.

Also, delayed treatment can lead to the the iris (thecoloured part of the eye) sticking to the front of the eye (cornea). This blocks the drainage area, so a 'drainage operation' is needed. This operation creates a channel between the inside of the eye and the outside (white part) of the eye.

What is the outlook for acute glaucoma?

The outlook is good if treatment is given promptly. The eye can recover, and laser treatment or surgery can prevent the problem coming back.

If the attack is severe or if treatment is delayed, there is a risk of complications (explained above).

Driving and glaucoma

Many people will be allowed to drive after recovering from acute glaucoma. 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 in both eyes, the law says that you must inform the Driver and Vehicle Licensing Authority (DVLA).

How can acute glaucoma be prevented?

Some people have an increased risk of getting acute glaucoma, due to a narrowing of the area where fluid normally drains from the eye. This is called a 'shallow anterior chamber' or 'narrow drainage angle'. Sometimes a narrow drainage angle is noticed at a routine eye examination. You may be told about this and advised to be careful with certain medications and eye drops (as above).

If you are at very high risk of acute glaucoma, you may be advised to have treatment such as laser iridotomy (above) to prevent it.

Be aware of the symptoms of acute glaucoma. Anyone who has a red eye with pain or vomiting, or a red eye with reduced vision, should get medical advice immediately. If you take a new medication or have eye drops to dilate the pupil, and then have symptoms of acute glaucoma, get medical advice straightaway; tell the 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, 15 Highpoint Business Village, Henwood, Ashford, Kent TN24 8DH
Tel: 01233 648170 Web: www.glaucoma-association.com