Double vision (also known as diplopia) can be caused by a number of different conditions, some of which can be serious. So it’s important to see your optician as soon as you experience symptoms.

What is double vision?

People with double vision (diplopia) will see two images of one object at the same time. It might look like the images are side by side, one above the other, or a mixture of the two. 

Some people are affected only occasionally, but for others it can be a constant problem.

You can experience diplopia in one eye (monocular) or both eyes (binocular). By covering one eye, you’ll be able to tell which type you have. If both eyes are involved, the double vision will disappear as soon as you cover either eye.

 However, if the double vision remains when you have one eye covered then you have monocular double vision.

If you have double vision, you may also experience:

  • Headaches
  • Feeling sick
  • Pain around the eyes
  • Pain with movement of eyes
  • Weakness in the eyes
  • Drooped eyelids

In some cases, double vision can be a symptom of a more serious medical issue, so it’s important to see your optician as soon as possible. If your double vision has accompanying pain or severe headache, you should visit your nearest A&E department.

What causes double vision which is present when both eyes are open?

Double vision in both eyes is known as binocular diplopia. Most cases of double vision occur when both eyes aren’t working together properly.

Each eye is surrounded by six muscles, which work together to ensure both eyes look toward the same point. Weakness in any of these muscles or their nerve supply can result in binocular double vision. Conditions such as multiple sclerosis or diabetes can affect the nerves in the eye.

Rarely, but much more seriously, diplopia can be caused by problems with the brain such as a stroke, aneurysm, and tumour. If the brain is affected by trauma, increased pressure or infection, double vision can be a symptom.

What causes double vision in one eye only?

Double vision in one eye is known as monocular and is least common of the two. 

This type is usually caused by an eye problem, such as cataract.

Cataracts are a common problem as we age, resulting in the lens in your eye becoming less clear, it can result in double vision in the affected eye

Temporary double vision

Episodes of temporary double vision happen for many reasons, like if you’ve been drinking too much alcohol, or if you’re over-tired. Short-term double vision is usually nothing to worry about, but if you experience double vision for longer than a few hours we’d recommend getting your eyes checked by your optician or GP.

Diagnosing double vision

If you’re experiencing symptoms of double vision, it’s important to see your optician or GP as soon as possible, as the causes and severity of double vision can vary. 

In order to diagnose double vision, your optician will carry out a thorough eye examination to investigate the health of your eyes and assess the coordination of your eye movements. During the examination, they may ask questions to understand the underlying causes of the double vision.

They may ask if your double vision symptoms are:

  • In one eye (monocular) or both eyes (binocular)
  • Constant or intermittent
  • Same or changing when you move your head or gaze
  • At near or far vision

What is the treatment for double vision?

As double vision can occur for a number of reasons, treatment will depend on its underlying cause, and could range from simple eye exercises or prism lenses to minor surgery.

Treatment for binocular double vision

In younger people double vision can often be treated with eye exercises but these are less effective as we get older.

 Glasses with lenses incorporating prisms can also be used to help the eyes align the two images into a single image. Sometimes, temporarily, an eye patch can help, as can minor surgery.

Treatment for monocular double vision

Because monocular diplopia is quite rare, treatment will depend very much on the cause.

Your optician will help to determine the right solution and suggest the best treatment for you. In some cases, they may recommend you visit your GP or hospital eye department for treatment.

If you experience double vision with pain or severe headache, you should go to your nearest A&E department.