Halos around lights: causes, what they mean and when to get checked

Halos are bright rings or glowing circles that appear around lights such as car headlamps, street lamps or a bedside lamp. They are usually most noticeable in dim conditions, because the pupil is larger and more light is scattered inside the eye.

The NHS includes seeing glowing rings, or halos, around lights in its list of cataract symptoms. Cataracts are a clouding of the lens, which scatters light on its way to the back of the eye. For many people halos are one of several complaints, alongside glare, hazy sight and trouble driving at night.

The less common but more urgent cause is a sudden rise in pressure inside the eye. The NHS says sudden glaucoma can cause intense eye pain, a red eye, tenderness around the eyes, rainbow-coloured circles around bright lights, blurred vision, nausea, being sick and headache.

The NHS describes cataracts as the lens in your eye becoming cloudy, causing blurred vision and loss of sight, and says it usually affects older adults. Symptoms usually develop slowly, and you will often have cataracts in both eyes, though the symptoms may be different in each eye.

Beyond halos, the NHS lists blurred vision, difficulty seeing at night, difficulty reading and watching television, eyes that are uncomfortable in or sensitive to light and glare, double vision, and colours that look faded, especially blue. Needing to change your glasses prescription more often than usual is another clue.

The NHS says to see an optician if you have symptoms of cataracts, and that if they think you have cataracts they will refer you to an eye specialist. It adds that cataracts do not usually need treatment straight away, and that surgery is usually done under local anaesthetic with the cloudy lens replaced by an artificial one, normally as a day case.

The NHS describes glaucoma as a condition where the main nerve connecting the eye to the brain becomes damaged. Most of the time it has no symptoms and develops slowly over many years, being picked up during routine eye tests. Halos are not a feature of the slow form.

Sometimes, though, the NHS says glaucoma can develop suddenly and cause symptoms such as intense eye pain, a red eye, tenderness around the eyes, seeing rainbow-coloured circles around bright lights, blurred vision, nausea and a headache. The advice is to call 999 or go to A&E, not to drive yourself, and to bring your medicines.

The practical point is to note the accompanying features. Halos on their own over months are one situation. Halos that arrive in an evening with a painful red eye, a headache and feeling sick are another.

The NHS pages cited here describe cataracts and glaucoma specifically. Halos can also be reported by people with dry or uneven tear film, so it is worth telling the optician about gritty, sore or watery eyes. The NHS dry eyes page lists blurry vision and sensitivity to light as symptoms.

Tell the clinician about any previous eye operation or injury, long-term steroid medicines, diabetes, and whether the halos affect one eye or both. The NHS lists past eye injury or surgery, steroid use, uveitis, being very short-sighted, smoking and diabetes among the factors that make cataracts more likely.

• One eye or both, and which lights trigger it.

• Whether it is worse in the dark or after eye drops.

• Any pain, redness, headache or nausea at the same time.

• Whether you have noticed glare when driving at night.

Halos and glare can make night driving uncomfortable. The NHS says you may still be able to drive with cataracts if your vision is good enough, and that you must let the DVLA know if your eyesight does not meet the minimum standards needed for driving. If you are not sure, it advises asking an optician.

Stronger glasses and brighter light for reading may help for a while, according to the NHS, but they do not remove the underlying cause.