Halos around lights at night: what they mean

Seeing bright rings, starbursts or a scattered halo around headlights and streetlights at night is one of the earliest signals that something has changed in the optics of the eye. It is rarely dangerous but is often the first symptom that brings a UK patient to my clinic. This guide explains the main causes and what to do next.

Why halos happen

The eye focuses light through the cornea and lens onto the retina. Any imperfection along that path — a dry spot on the cornea, a clouded lens, an off-centre pupil, a laser-treatment zone — scatters some of the incoming light. Around bright point sources against a dark background (headlights on a wet road, streetlights, LED signs), that scatter is visible as halos, glare and starbursts.

The commonest causes

**Early cataract.** In UK adults over 55, the top cause is early cataract — the natural lens develops subtle opacities that scatter light. Halos are typically worst on wet roads at night. Vision by day may still be 6/6. See our what is a cataract guide.

**Dry eye and blepharitis.** An unstable tear film breaks up between blinks and scatters light. Halos come and go with each blink. Treatment of the underlying dry eye removes them completely.

**After LASIK, PRK or SMILE.** Around 3–6 months after refractive surgery, especially in patients with large pupils, some scatter around the treatment zone is normal. It usually settles by 6–12 months. Persistent halos may indicate residual refractive error and respond to enhancement.

**After cataract surgery with a multifocal or EDOF lens.** Multifocal lenses split light between distance and near foci, so a mild ring of light around headlights is a designed trade-off. Most patients adapt within 3–6 months. See our premium lens cataract surgery guide.

**Angle-closure glaucoma — an emergency.** Sudden severe halos with red painful eye, nausea, vomiting and blurred vision is angle-closure glaucoma. Attend eye casualty or A&E immediately.

**High refractive error.** Untreated short-sightedness or astigmatism causes glare and halos at night that resolve entirely with correct spectacles or contact lenses.

**Migraine aura.** Bright zigzag or coloured shapes lasting 20–30 minutes are migraine, not a lens problem.

When halos are urgent

See an eye specialist the same day if halos come with:

- Severe pain, redness or nausea (possible angle-closure glaucoma)

- Sudden loss of vision or a shadow across vision (possible retinal detachment)

- A haze over the whole eye and reduced daytime vision (possible corneal oedema)

How halos are investigated

In a night-vision-focused consultation I would typically:

- Measure vision at distance under standard and low-contrast conditions

- Check refraction — including small residual astigmatism

- Perform corneal topography and aberrometry

- Measure pupil size in scotopic (dim) conditions

- Examine the tear film and lens with a slit lamp

This identifies the cause in one visit and separates the treatable causes (cataract, dry eye, refractive error) from those that just need reassurance and time (post-refractive-surgery adaptation).

Next steps

If halos have started to affect your night driving, do not wait until you fail the DVLA standard — you can be assessed and treated privately within 2–4 weeks. Book a consultation or call **020 3137 3237** to have your night vision assessed.