Narrow-angle (angle-closure) glaucoma: symptoms, emergency signs and treatment

Glaucoma is a group of eye conditions in which the optic nerve, the nerve that connects the eye to the brain, becomes damaged. The NHS explains that it is usually caused by a build-up of pressure in the eye, which happens when the fluid in the eye cannot drain as it should.

Glaucoma UK describes how this works in the angle-closure type. The front of the eye contains a watery fluid called aqueous humour. It is made inside the eye and leaves through tiny drainage channels located in the angle between the iris (the coloured part of the eye) and the cornea (the clear window at the front). In angle closure the iris comes too far forward and closes that drainage angle, so the fluid cannot get out and the pressure inside the eye rises.

Angle closure can happen suddenly, which is called acute angle closure, or slowly over weeks, months or years. The terms can be confusing. Glaucoma UK points out that people often say acute angle closure glaucoma, but strictly the word glaucoma applies only if the optic nerve is damaged during the attack. When the attack is treated quickly, damage to the optic nerve is unlikely.

Most types of glaucoma cause no symptoms for years, and the NHS says glaucoma is usually picked up during routine eye tests. Acute angle closure is different because it announces itself. Glaucoma UK lists the symptoms as intense eye pain (usually in just one eye), headache, feeling or being sick, seeing coloured rings around lights, a red eye, and blurred, foggy or reduced vision. The NHS glaucoma page lists a very similar group, including rainbow-coloured circles around bright lights and tenderness around the eyes.

The NHS says to call 999 or go to A&E if you develop symptoms of glaucoma suddenly, and not to drive yourself; ask someone to drive you or call an ambulance, and take your medicines with you. Glaucoma UK similarly advises going to accident and emergency or an emergency eye clinic straight away.

Not every episode is dramatic. Glaucoma UK describes a series of short spells of sub-acute angle closure with mild symptoms that can disappear after a night's sleep and then come back. This is called intermittent angle closure. Because it may be a sign that a more serious attack is possible, mild recurring spells of this kind are worth reporting to a GP, optician or eye clinic rather than waiting for them to settle.

Other conditions can look similar. The NHS notes that uveitis and an eye injury can cause similar symptoms, which is one reason a painful red eye needs to be examined by a professional rather than self-diagnosed.

• Intense pain in one eye, often with a headache.

• A red eye and blurred, foggy or reduced vision.

• Seeing coloured rings or rainbow halos around lights.

• Feeling sick or being sick.

• Brief mild episodes that settle after sleep and return.

Glaucoma UK says acute angle closure is usually linked to having small eyes with less space inside the front of the eyes. People are more likely to develop it if they are a woman, aged over 40, Asian (especially Chinese), from a family with a history of angle closure, or long sighted.

The same source explains the trigger. Anything that makes the pupil bigger pushes the iris forward and could cause acute angle closure. Most of the time such things are perfectly safe, and examples listed include dilating eye drops (such as those used for diabetic eye examinations), dim lighting, sudden excitement or adrenaline rushes, and some medicines, for example some antidepressants. An injury to the eye can also cause angle closure. Glaucoma UK advises checking the leaflet that comes with any medicines or talking to a pharmacist, GP or eye doctor if you are concerned.

The NHS adds a broader set of risk factors for glaucoma in general: being over 50, having a brother, sister or parent with glaucoma, being from a Black African, Caribbean or Asian background, and having other conditions such as short-sightedness, long-sightedness or diabetes.

The NHS says glaucoma is usually found at a routine eye test, often before it causes symptoms, and that if you are told you have glaucoma you should be referred to a specialist eye doctor (an ophthalmologist) for further tests. It recommends regular eye tests, at least every 2 years, and says people at higher risk, for example with a close relative who has glaucoma, may be advised to have them more often.

In an emergency, assessment happens at an eye casualty or A&E with specialist eye review. In people who are only at risk of angle closure, an eye doctor can assess the drainage angle and decide whether preventive treatment is advisable. Glaucoma UK notes that if you are at high risk of angle closure, an eye doctor might offer lens extraction surgery or laser iridotomy to prevent future angle closure.

Glaucoma UK explains that acute angle closure must be treated quickly to stop pain and prevent sight loss. Treatment aims to open the drainage angle so fluid can leave the eye and the pressure falls. A doctor will first give eye drops to make the pupil smaller, which helps push the iris back and opens the drainage angle. They might then give tablets, injections or eye drops to reduce the amount of fluid the eye makes, and steroids to reduce swelling.

Once the pressure is low enough, an eye doctor can give laser treatment, surgery or both. These help lower eye pressure further and help prevent the drainage angle closing again.

Glaucoma UK says that if you get treatment quickly for acute angle closure you have a good chance of keeping good sight, and that the longer you delay or must wait for treatment, the more sight you are likely to lose. After an episode you will usually have regular eye clinic appointments so the eye doctor can check eye pressure, eye health and sight, and decide whether treatment needs to change.

The NHS says there is currently no cure for glaucoma, but treatment can slow the damage and help stop vision getting worse, and it stresses that missing follow-up appointments is best avoided. If sight is affected, it can be difficult to come to terms with, and the NHS points to support groups and national charities including Glaucoma UK and the RNIB.

An acute attack is treated through A&E or an emergency eye clinic on the NHS, and follow-up is usually with a hospital glaucoma or ophthalmology service. Routine sight tests are carried out by an optometrist at a local optician, and the NHS notes that some people can receive free NHS eye tests.

Some people choose to see a private ophthalmologist for assessment of their drainage angle, preventive laser, or a second opinion. The examination, laser iridotomy and cataract-type surgery are the same procedures in either setting, so the practical differences are mostly waiting time and choice of surgeon. Whoever you see, it helps to ask who you should contact urgently if symptoms return.