Double vision (Diplopia)

Symptoms of double vision

If you have double vision (diplopia), you’ll see two images of the same object at once. They might appear side by side, one above the other, or both. For some people, it comes on suddenly and goes away again. For others, it’s more constant. You might also notice other symptoms, such as headaches, feeling sick, dizziness or pain around or when moving your eyes. It can also come with eye weakness, also known as blurry vision, eye pain or a droopy eyelid.

What causes double vision (diplopia)?

Diplopia is often a sign of another underlying health issue. We’ve grouped the main causes of double vision into the categories below.

Problems with the eye itself

Diplopia is a sign of a few different eye conditions which might damage the cornea (the clear part on the front of your eye) or the lens (which helps focus light onto the retina at the back of your eye).

Eye problems that can cause double vision include:

• Astigmatism

• Dry eye syndrome

• Cataracts

• Macular degeneration

• Glaucoma

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 lazy eye (strabismus).

Problems with 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 in the 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.

Medication side effects

Double vision may be a side effect of certain medication. Talk to your GP or pharmacist 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 cannabis can cause double vision. It can also happen when you're extremely tired.

How is double vision diagnosed?

Because many different things can cause diplopia, your doctor or optometrist will use a range of double vision tests to find the underlying issue. These may include the following techniques:

Medical history

Your eye specialist 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 Canada, optometrists may use tests like OCT scans, slit lamp test and dilated eye exams, among others.

Learn more about eye exams

Imaging 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.

Blood tests

Blood tests can help with diagnosing a few conditions that can cause double vision, including some cancers, immune system disorders and neurological conditions.

How is double vision treated?

The right treatment for double vision depends on what’s causing it. If it’s caused by something like mild strabismus (lazy eye or squint), corrective glasses might be enough. But if another health issue such as diabetes is the cause, you’ll likely need to control your blood sugar, adjust your lifestyle and possibly begin insulin therapy. Seeing an eye doctor is important to determine the specific cause before receiving treatment.

Below, we’ve listed some common ways to manage the double vision itself. However, if another condition is responsible, you’ll also need treatment that addresses that specific cause.

Prism 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 into your weaker eye.

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.

Surgery for double vision

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 assessment and treatment.