Double Vision (Diplopia)

What is double vision (diplopia)?

Double vision happens when you look at a single object but see two images. The medical term for this condition is 'diplopia'. For some, double vision is only temporary. For others, it may come and go. And for some, it happens constantly. It can start suddenly or develop gradually over time.

Living with double vision

Having double vision can be distressing and disruptive. It can make everyday tasks like driving, playing sports, using a computer, reading, or watching TV difficult, uncomfortable or even dangerous.

Let’s get your vision sorted

Noticed your eyes hurting, or a change in your sight? Whether it’s something new or something that’s been bothering you for a while, we’re here to help.

Types of double vision

There are three main kinds of diplopia or double vision.

Double vision in one eye (monocular diplopia) 

This is when you get double vision in one eye. If you close the affected eye, your vision in the other eye is clear, and the double image goes away. It’s usually caused by a problem within one of the eyes.
Learn more about eye conditions.

Double vision in both eyes (binocular diplopia) 

This is when you see two images of the same object with both eyes open. If you close either eye, your vision will clear up. It's often a sign that there's a problem with how your eyes work with each other, or an issue with your nerves or brain.

Temporary double vision 

You may get temporary double vision after drinking too much alcohol or taking other intoxicants. It can also happen when you're extremely tired. You may also get double vision after a knock to the head ‑ this needs to be checked by a medical professional.

You can also experience voluntary double vision, which is when you intentionally cross your eyes. For example, when looking at a stereogram image.

Diplopia may need emergency care

Double vision isn’t usually a medical emergency, but there are times when you should seek urgent care. 
 
Contact your GP for an urgent appointment or call Healthline on 0800 611 116 if you have double vision with pain in or around the eye, if it started suddenly, or if it hasn’t gone away after a few hours. 
 
Call 111 or go to the emergency department straight away if you have a severe headache and enlarged pupils along with double vision, if it began after a head injury, or if you also have slurred speech, confusion or dizziness.

What causes double vision (diplopia)?

Diplopia is often a symptom of other health conditions. We've divided the main double vision causes into the following groups.

Problems with the eye

Diplopia can be a symptom of several eye conditions that may affect the cornea (the clear outer surface of the eye) or the lens (which focuses light onto the retina at the back of the eye). Eye problems that can cause double vision include astigmatism, cataracts, dry eye syndrome, glaucoma and macular degeneration.

Problems with the eye muscles 

If the muscles that move your eyes aren’t working together, it can lead to double vision. This can be caused by conditions like Graves' disease, myasthenia gravis, head injuries or squint (strabismus).

Problems affecting your nerves 

Problems with the nerves linking your eyes and brain can cause double vision. This can happen with conditions like cranial nerve palsy, multiple sclerosis, Guillain‑Barré syndrome, or diabetes.

Problems affecting your brain 

Double vision can be linked to strokes, tumours, aneurysms, injuries, or infections in the brain, all of which need urgent care. It can also affect people with migraine headaches.

Problems related to contact lenses or glasses 

Double vision can happen if your contact lenses or glasses prescription aren't quite right.

Side effects of medication 

Double vision may be a side effect of certain medicines ‑ let your GP or pharmacist know if you notice double vision after starting a new prescription.

Other health conditions 

Several other health conditions can also cause double vision including Wernicke's syndrome, Lyme disease, and some kinds of cancer.

Double vision caused by lifestyle 

Certain lifestyle factors, such as drinking too much alcohol or consuming other intoxicants can cause double vision. It can also happen when you're extremely tired.

How is double vision diagnosed?

Because diplopia can be caused by many different things, your doctor or optometrist will use several methods to get to the bottom of it. Double vision tests may include the following techniques.

Medical history 

Your optometrist will ask when it started, what you’re seeing, what medication you take, and if symptoms follow a pattern or happen during certain activities.

Double vision tests 

At our stores in New Zealand, optometrists may use tests like OCT scans, slit lamp test, and dilated eye exams, among others.  
Learn more about eye tests.

Blood tests 

Blood tests might be used to check for a variety of illnesses, including cancers, immune system disorders and neurological conditions.

Scans 

You may be referred for imaging scans (such as MRI or CT scans) which help build a picture of what's happening inside your brain.

How is double vision treated?

The right treatment for diplopia depends on its underlying cause. If it’s caused by a mild strabismus (squint), you may only need corrective glasses. But if diabetes is making you have double vision, you’ll likely need to manage your blood sugar, make lifestyle changes, and possibly start insulin injections. 
 
Below, we’ve outlined some common ways to manage the double vision itself. However, if it’s linked to another condition, you’ll also need treatment that targets that specific issue.

Prism lenses (including Fresnel lenses) 

Prism lenses are layers that can be stuck onto your normal glasses or even built into the lens. If your diplopia is caused by problems with eye alignment, the prism bends light to shift the image of the object, correcting the double vision.

Blocking vision in one eye 

Diplopia might be due to a weakness in one eye. Your optometrist might recommend blocking vision in your healthy eye, forcing the weaker eye to work harder and improving your vision over time.

Botox injections 

Botulinum toxin (Botox) injections can help by relaxing the muscles in the stronger eye. This gives the weaker eye a chance to recover and realign.

Double vision surgery 

Your optometrist might recommend surgery if muscle weakness or eye conditions like cataracts or keratoconus are causing double vision. It might also be used to treat a droopy eyelid.

Referral to specialists 

If your GP or optometrist believes that another health issue ‑ such as a brain tumour, diabetes or hormonal disorder ‑ is causing your double vision, they’ll refer you to a relevant specialist for further investigation and treatment.