If you sometimes see bright circles surrounding a source of light — like a street lamp or headlamp — this is known as seeing 'halos'. Often, this is a normal response to bright lights, but it can also be a symptom of an underlying eye condition which may be affecting your vision. 

How do you know whether it is a problem requiring immediate treatment, or a common condition such as a clouding of your lens, called cataract? Your optometrist will perform an assessment to establish the cause and, if necessary, refer you to a specialist for further treatment.

Why do halos around lights occur?

Halos typically occur in dim or dark surroundings and are most obvious during night-time. Usually they happen due to a distortion of light beams — something has come in between the source of light and the back of your eye — such as glasses or contact lenses. If you experience other symptoms alongside halos around lights, it can be a sign of something else. 

Sudden onset halos

The sudden appearance of halos around lights is one of the symptoms of acute angle-closure glaucoma. This is a medical emergency that requires immediate treatment to prevent permanent vision loss.  Acute glaucoma causes the pressure inside your eye to increase rapidly. The increased pressure can come and go, and some people get short bursts of pain or discomfort and blurred vision or halos. This can happen when your pupils get bigger, so you may notice it at night or when you are in a dark room, such as a cinema. Other symptoms of this condition include severe eye pain, blurred vision, nausea, vomiting, and headaches. You should seek immediate medical attention if you have these symptoms.

Blurry vision and halos

Blurred vision and halos around lights could be signs of photokeratitis (sunburn of the eyes) or keratoconus (thinning and bulging of the cornea).1, 2 If the symptoms are persistent, it’s a good idea to get the opinion of an optometrist. 

Sharp eye pain and halos

People who experience migraines may see halos around lights and experience sharp or deep eye pain. This could also indicate that you have acute angle-closure glaucoma or uveitis. You should see an optometrist to rule out serious and potentially treatable causes of these symptoms.

What eye conditions can cause halos around lights?

Some of the eye diseases that can cause a person to see halos around lights are listed below:

Halos around lights and acute glaucoma

Seeing halos around lights at night, especially halos with rainbow rings, is one of the early warning signs of an acute form of glaucoma. If this is accompanied by blurred vision or severe eye pain, it could indicate an acute episode of glaucoma that requires immediate treatment.

Halos around lights and cataracts

People with cataract in their eyes may start seeing halos around lights due to the clouding of the lens, which leads to a bending of light rays entering the eye. Cataract surgery can usually take care of the problem.

Halos around lights and Sjogren’s syndrome

This is an immune disorder in which the most common symptoms are dry eyes and dry mouth. Dry eyes can lead to an irregular surface of the eye and scattering of light, causing you to see halos.

Halos around lights and diabetic retinopathy

One of the symptoms of advanced diabetic retinopathy is halos around lights, which occur due to a distortion of vision from the damaged retinal vessels in the back of the eye. This condition can be detected during an optical coherence tomography test (or OCT scan). 

When should I get an eye test?

It’s important to get your eyes tested at least every two years, even if you think your vision is perfectly fine. Regular testing allows your optometrist to monitor any changes happening in your eyes, and begin treatment as early as possible if you need it. If you have been experiencing halos around lights, it’s a good idea to get your eyes tested as soon as possible, to rule out any possible issues with your eye health. 

What is an OCT scan?

An OCT scan (or optical coherence tomography scan) is one of the methods your optometrist can use to monitor your eye health during a test at Specsavers. It’s a quick procedure that uses light to make a layered image of the back of your eye.

An OCT scan gives us an incredibly accurate depiction of what is happening inside your eye and can help us detect some of the eye conditions that cause halos around lights. These scans can aid us in identifying signs of an eye condition before it has any noticeable symptoms or impact on your vision. We can also store these images to check back for any changes over time. 

Find out more about eye symptoms and the diagnosis of eye diseases with optical coherence tomography on our dedicated OCT resources. You can also book an appointment with a Specsavers optician for a more detailed explanation of the process.

References

1. Boyd, K. (2019). What Is Keratoconus?. [online] American Academy of Ophthalmology. Available at: https://www.aao.org/eye-health/diseases/what-is-keratoconus [Accessed 4 Dec. 2019]. 

2. Porter, D. (2019). What is Photokeratitis — Including Snow Blindness?. [online] American Academy of Ophthalmology. Available at: https://www.aao.org/eye-health/diseases/photokeratitis-snow-blindness [Accessed 4 Dec. 2019].