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Sudden double vision: what causes it and when is it an emergency?

Seeing two of everything is frightening, and it makes walking, reading and driving difficult or unsafe. Sudden double vision has many causes. Some are minor and settle by themselves; some are signs of a serious problem in the brain or blood vessels that needs emergency care. This guide helps you understand the difference and what to do. For optic nerve and eye-movement problems in general, see optic nerve and double vision problems.

Is it an emergency?

Call 108 and go to the nearest hospital emergency department at once if double vision comes with any of these:

• weakness or numbness of the face, arm or leg
• slurred speech, confusion or difficulty understanding
• difficulty walking, dizziness or loss of balance
• a sudden, severe headache, the worst you have had
• a drooping eyelid or one pupil larger than the other
• difficulty swallowing or breathing
• a recent head injury

These can be signs of a stroke, bleeding or a bulging blood vessel (aneurysm) in the brain, or another serious condition, where every minute counts.

New double vision without these signs still needs to be checked the same day. Emergency eye care at ReNew Vision is available 24 hours; see eye emergency. If you are far from Vasco, go to the nearest hospital emergency department rather than travelling.

First: is it one eye or both eyes?

Try this simple check. Look at a single object, such as a light or a word, and cover one eye, then the other.

• The double image disappears when either eye is covered: this is binocular double vision. The two eyes are not pointing at the same spot. The cause is usually in the nerves or muscles that move the eyes, or in the brain.
• The double image stays in one eye with the other eye covered: this is monocular double vision. The cause is usually in that eye itself, such as a cataract, dry eye, an irregular cornea or the wrong spectacles. It is rarely an emergency, but it still needs an eye check.

What causes sudden binocular double vision?

Weakness of a nerve that moves the eye

Three nerves on each side control the eye muscles. In people over about 50, especially with diabetes or high blood pressure, a small blood vessel feeding one of these nerves can fail, and the eye cannot move fully in one direction. This often recovers by itself over weeks to a few months. But the same picture can come from an aneurysm, raised pressure in the head or a growth, especially when the eyelid droops, the pupil is large, there is severe headache, or the person is younger. So every new nerve weakness needs a prompt examination, and often a scan.

Thyroid eye disease

An overactive (or sometimes underactive) thyroid, or the immune condition behind it, can swell and stiffen the eye muscles. Double vision usually comes on over weeks, often with gritty, staring or bulging eyes and puffy lids. It is treated together with the thyroid doctor.

Myasthenia

Myasthenia is a condition in which muscles tire easily. In the eyes it causes drooping eyelids and double vision that come and go and get worse later in the day or when tired. If it affects swallowing, speech or breathing, it is an emergency.

Stroke, bleeding and other brain problems

A stroke in the brainstem, bleeding, raised pressure inside the head or inflammation can all cause double vision, usually with other symptoms. These need emergency care.

Problems in the eye socket

A blow to the eye can fracture the thin bone of the socket and trap a muscle; an infection in the socket causes painful swelling, redness and fever. Both need urgent care.

An old squint that has stopped being controlled

Some people have had a small squint since childhood that the brain controlled for years. With age, illness or tiredness, control can slip and double vision appears, usually more gradually. Spectacles with prisms or squint surgery may help; see squint surgery.

What happens at the eye examination?

1. The eye doctor asks when the double vision started, whether the images are side by side or one above the other, whether it changes through the day, and about diabetes, blood pressure, thyroid problems and recent injury.
2. Vision, pupils and eyelids are checked.
3. Eye movements are tested in each direction, and the eyes are covered in turn to measure any misalignment.
4. The optic nerves are examined, often after dilating drops.
5. The eye doctor explains the likely cause and what is needed next: watching and waiting, blood tests, a brain scan, or an urgent referral to a neurologist or emergency department. Brain scans are not done at ReNew Vision; if you need a scan or blood tests, the eye doctor explains why and what the next step is.

What can I do while it settles?

• Cover one eye. An eye patch, or tape over one lens of your spectacles, stops the double image and makes walking safer. Switch eyes from time to time if the eye doctor advises.
• Do not drive or ride while you see double, even with one eye covered, until the eye doctor says it is safe.
• Keep your sugar and blood pressure controlled, which helps a nerve weakness from diabetes or blood pressure recover.
• Keep your follow-up visits, so that recovery is checked and any change is found early.

The eye doctor may also suggest temporary prism lenses on your spectacles while the double vision settles.

Will the double vision go away?

It depends on the cause. Nerve weakness linked with diabetes or blood pressure often improves within about three months. Thyroid and myasthenia-related double vision improves with treatment of the condition. If double vision remains after the cause has settled, prism spectacles or squint surgery can often help.

Double vision in children

Young children rarely complain of double vision; they may close or cover one eye, tilt the head, or suddenly develop a squint. A new squint in a child, especially with headache, vomiting or unsteadiness, needs to be seen quickly.

Getting checked in Vasco

ReNew Vision Eye Hospital, 2nd floor, Pai Hospital building, Vaddem Merces Road, Vaddem, Vasco da Gama. Eye OPD Monday to Saturday, 4 pm to 7 pm, and emergency eye care 24 hours. Call or WhatsApp 072489 88039. Do not drive yourself; bring someone with you, along with your medicine list and recent sugar, BP and thyroid reports. Directions are on the visit page.

Questions patients ask

Is sudden double vision a sign of stroke?

It can be, especially with weakness or numbness, slurred speech, confusion, loss of balance or a severe headache. Then call 108 and go to the nearest hospital emergency department at once. Without these signs, still have it checked the same day.

Can diabetes cause double vision?

Yes. Diabetes can damage a small blood vessel feeding one of the nerves that move the eye, causing sudden double vision. It often recovers over weeks to months, but every new case needs an examination to rule out other causes.

Can double vision go away on its own?

Sometimes. Double vision from a nerve weakness linked with diabetes or blood pressure often improves within about three months. Other causes need treatment, so always have new double vision examined.

Can I drive with double vision?

No. Do not drive or ride while you see double, even with one eye covered, until the eye doctor tells you it is safe.

Why do I see double only when I am tired?

Double vision that comes when you are tired or late in the day can be an old squint that the eyes can no longer hold straight, or a sign of myasthenia, especially with drooping eyelids. Both need an eye examination.

This page is general eye-health information, not personal medical advice. Your eye doctor advises you after examining your eyes.