Narrow angles in the eye: what it means and when it needs treatment

The eye makes a watery fluid, aqueous humour, which flows through the pupil and drains away through tiny channels called the trabecular meshwork. Glaucoma UK explains that the meshwork sits in the angle between the cornea and the iris, often called the drainage angle, and that if this angle is narrow it can reduce the effectiveness of fluid escaping the eye. Some eyes naturally have a narrower drainage angle, for example eyes that are smaller or long-sighted, and people of particular ethnic origins.

Having narrow angles is an anatomical finding, not a disease in itself, but it matters because the angle can close. The NHS describes glaucoma as a condition where the main nerve connecting the eye to the brain becomes damaged, usually caused by a build-up of pressure when fluid cannot drain as it should. If a narrow angle closes, even partially or intermittently, pressure can rise and damage the optic nerve. Glaucoma UK describes how the increase in pressure damages the optic nerve by reducing the blood supply and by pressing on the nerve itself.

These terms describe a spectrum. Narrow angles describe the shape. Angle closure describes the angle actually becoming blocked. Primary angle closure glaucoma (PACG) describes closure that has led to glaucoma damage. NICE CKS divides glaucoma according to whether the angle between the iris and cornea is open or closed, and explains that acute angle closure may quickly progress to glaucoma.

Glaucoma UK says PACG can be chronic or acute. Chronic angle closure develops slowly, usually without symptoms, as the drainage angle gets smaller and the eye pressure slowly rises, and is usually identified during a routine eye test. Acute angle closure happens when a blockage is sudden and causes the pressure to rise very high, very quickly.

NICE CKS adds that most people with PACG have asymptomatic chronic disease, which is why routine eye tests matter.

Glaucoma UK lists risk factors for primary angle closure: age, as it gets more common with age, with around 20 in 5,000 people over 40 in the UK having primary angle closure and around 47 in 5,000 over 70; family history, with brothers, sisters and children around four times more likely than other people to develop it; ethnicity, with people of east Asian origin more likely than people of European origin; gender, with women around one and a half times more likely than men; and long sight.

NICE CKS points to the same features when describing who should be suspected of acute angle closure: a person who is female, Asian, long-sighted or of older age. The NHS adds that your risk of glaucoma generally may be higher if you are over 50, have a close relative with glaucoma, or are from a Black African, Caribbean or Asian background, and that short-sightedness, long-sightedness or diabetes are associated conditions. If a close relative has glaucoma, you may be advised to have eye tests more often.

Most people with narrow angles feel nothing. The NHS says glaucoma does not usually have symptoms and develops slowly over many years, usually being picked up in routine eye tests. When the angle begins to close, symptoms can appear.

Glaucoma UK describes acute primary angle closure as causing intense pain, redness of the eye, blurred or reduced vision, headache and nausea, which tends to be very painful, and says to seek medical advice immediately because the sudden rise in pressure can cause permanent damage to sight. It also describes sub-acute attacks, a series of milder attacks with blurred vision, halos around lights and headaches that come and go, and says it is very important to seek immediate medical advice as it might be a warning of a future serious attack.

NICE CKS adds that people may have a history of episodes of blurred vision, headaches or eye pain associated with nausea and seeing halos around lights, typically in the evening and relieved by sleeping, and that during an acute attack the pupil may be semi-dilated and fixed and the eye tender and hard.

The NHS says to call 999 or go to A&E if you develop symptoms of glaucoma suddenly, as this is a medical emergency that may require immediate treatment, and not to drive yourself to A&E. Typical symptoms are intense eye pain, a red eye, tenderness around the eye, rainbow-coloured circles around bright lights, blurred vision, feeling or being sick and a headache.

NICE CKS says that if acute angle closure is suspected the person should be admitted for ophthalmology assessment. Glaucoma UK says that acute angle closure is initially treated with drops and an intravenous injection to lower the eye pressure, followed by a laser or surgical procedure to bypass the blockage and prevent it happening again, and that if diagnosed and treated without delay there may be an almost complete and permanent restoration of vision.

Glaucoma UK says that if you have narrow angles and are therefore at greater risk of developing PACG, this will be identified at a routine eye test. The NHS recommends regular eye tests, at least every 2 years, with more frequent tests for those at higher risk, and says some people can receive free eye tests on the NHS. An optometrist who suspects narrow angles will refer you to an ophthalmologist, who examines the drainage angle with a special lens, measures eye pressure and checks the optic nerve and visual field.

The result may be one of three situations: narrow angles with normal pressure and a healthy nerve, closure with raised pressure but no nerve damage, or closure with glaucoma damage. Each has a different level of urgency and a different plan.

Glaucoma UK says the eye doctor may use laser treatment to help prevent a narrow angle closing completely. Its laser page explains that laser iridotomy and iridoplasty are used to treat angle closure glaucoma or narrow angles. In iridotomy, a small hole is made in the iris with a laser, which allows the iris to return to its original position and opens up the natural drainage channel so that fluid can drain and pressure can fall.

It describes the treatment as done under local anaesthetic, so you are awake but the eye is numb, with most people able to go home the same day, and eye drops may be given afterwards to reduce swelling. Vision may be blurry for a short time, and follow-up appointments are important. Glaucoma UK also notes that the same procedure is normally performed in the other eye to prevent an attack of acute angle closure in that eye.

If glaucoma damage is present, treatment may also include eye drops to lower pressure, further laser or surgery. The NHS says there is currently no cure for glaucoma but treatments can slow damage and help stop vision getting worse, and that follow-up appointments should not be missed. NICE CKS adds that treatment of glaucoma is normally initiated and monitored by specialists, and that its mainstay is to reduce intraocular pressure.

Keep to your follow-up schedule and tell the eye team about any new symptoms. Tell any doctor, pharmacist or dentist that you have narrow angles before starting new medicines, because some medicines that widen the pupil can precipitate an attack, and ask whether a given medicine is suitable. Know the warning signs of an attack so that you can act quickly.

Glaucoma UK provides information, a helpline and support groups for people with glaucoma and related conditions, and the NHS points to the Royal National Institute of Blind People for support with sight loss.