Double Vision: One Eye or Both, Causes and When It's Urgent

Double vision usually comes from one of two places, and covering one eye tells you which. If the second image goes away when you cover either eye, your eyes are most likely out of line: when the eyes are misaligned, the brain receives two different images. If it stays with one eye covered, the cause is in the open eye, and a cataract is one possibility. Call 911 if double vision starts suddenly, even if it goes away, or if it comes with a pupil that looks different, eye pain, a severe headache or stroke signs such as face drooping, weakness or trouble speaking. Double vision that came on gradually still needs a same-day exam: call us at 310-828-2010 for an urgent eye care visit, or go to an emergency room when we're closed.

Key takeaways

Cover each eye in turn: double vision that clears with either eye covered means misaligned eyes, and double vision that stays comes from the open eye.
A cataract is one cause of double vision in one eye, and misaligned eyes can come from stroke, diabetes, a brain aneurysm or eye muscle or nerve problems.
Double vision that came on gradually, with no other warning signs, still needs a same-day exam, or an emergency room when we're closed.
Call 911 if double vision starts suddenly, even if it goes away, or comes with a pupil that looks different, eye pain, a severe headache or stroke signs.

Is your double vision in one eye or both?

Cover one eye, then the other, and notice when the double image goes away. Strabismus is a condition in which both eyes do not look at the same place at the same time, and when the eyes are misaligned, the brain receives two different images. Covering either eye leaves the brain with a single image, so this kind of double vision goes away.

Double vision that stays when the other eye is covered comes from the eye that is still open. That points the exam toward the eye itself, such as its lens or cornea. Below, "double vision in one eye" means the kind that stays with the other eye covered, and "double vision in both eyes" the kind that goes away when either eye is covered.

What causes double vision in one eye?

A cataract, a cloudy area in the lens of the eye, is one cause: the National Eye Institute lists seeing double among cataract symptoms and notes that it sometimes goes away as the cataract gets bigger.

Cataracts are very common in older adults. By age 80, more than half of all Americans either have a cataract or have had cataract surgery, and other symptoms include blurry or cloudy vision, faded colors, glare and halos around lights.

The exam also looks at the cornea, the clear front of the eye. In keratoconus, the cornea thins and bulges into a cone shape, and vision can become more distorted as it progresses. Our post on what keratoconus vision looks like walks through those changes, and our keratoconus care and cataract monitoring cover both conditions.

What causes double vision in both eyes?

Double vision that goes away when you cover either eye happens when the eyes don't line up. Strabismus can come from problems with the eye muscles, the nerves that carry signals to them, or the control center in the brain, and older children and adults can develop it too. It is more likely after a stroke or head injury, and in people whose parents or siblings have strabismus. Causes of new double vision in both eyes include:

Cause	What happens	Typical clues
Stroke	Damage to the nerves or muscles that move the eyes	Starts suddenly and may come with face drooping, arm weakness, trouble speaking or loss of balance
Diabetes	Damage to a nerve of the head, called a cranial neuropathy, which can cause eye problems	Double vision, aching behind one eye or trouble focusing; it starts suddenly, mostly in older adults, and most people recover within a few weeks or months
Brain aneurysm	A weak spot on an artery in the brain balloons and fills with blood; a large, growing one may press on nerves	Pain above and behind the eye, a widened pupil, vision changes or double vision; a sudden, severe headache if it bursts
Myasthenia gravis	A chronic disease that causes weakness in the muscles you control, including the eye muscles	Drooping of one or both eyelids, blurred or double vision; it most often affects women under 40 and men over 60
Graves' ophthalmopathy	In Graves' disease, an autoimmune disorder that can cause an overactive thyroid, the immune system attacks the muscles and other tissues around the eyes in more than 1 in 3 people	Bulging eyes, blurred or double vision
Convergence insufficiency	The eyes have trouble working together on nearby objects	Blurry or double vision up close, such as when reading or using a phone, with tired or sore eyes
Giant cell arteritis	Inflammation of the arteries, usually in the scalp, neck and arms; it almost always affects people over 50	Headaches, pain and tenderness over the temples, jaw pain, double vision or vision loss

These clues overlap (aching behind one eye can come from diabetes or a growing aneurysm), so sudden double vision still means calling 911, even if you have diabetes.

In a young child, the brain can learn to ignore the image from a turned eye, so a long-standing eye turn may not cause double vision, and untreated, the turned eye can end up with permanently reduced vision. That loss of vision is called amblyopia; it starts in childhood, and strabismus is one of the conditions that can lead to it.

Is sudden double vision an emergency?

Yes. Call 911 for double vision that starts suddenly, even if it goes away: the American Stroke Association lists double vision among the sudden vision changes that can signal a stroke. Call 911 too if double vision comes with any of these:

Face drooping, numbness or weakness of the face, arm or leg, trouble speaking, confusion, sudden dizziness or loss of balance
Sudden loss of vision in one or both eyes
A pupil that looks different from the other one, eye pain (such as pain above and behind the eye) or a severe headache; a brain aneurysm can cause all three
Trouble breathing in someone with myasthenia gravis. When the breathing muscles weaken, it is called a myasthenic crisis, and it requires immediate emergency medical care

A drooping eyelid with a pupil that looks different, eye pain or a severe headache is a 911 call too, even without double vision.

Double vision that has come on gradually, with none of those signs, still needs an exam the same day. Call our office immediately during office hours (Monday 10 to 5, Tuesday through Friday 8 to 5), and go to an emergency room when we're closed. The same applies to a droopy eyelid that has come on gradually along with double vision; if either one started suddenly, call 911.

If you're over 50 and the double vision comes with a new headache, tenderness over your temples or jaw pain, tell whoever examines you, whether that's the emergency team or us: giant cell arteritis needs early treatment, because without it there is a risk of permanent vision loss or stroke.

How is double vision treated?

Treatment follows the cause. With a cataract, a new prescription for glasses or contact lenses can help early on, and surgery is the only way to remove it. With keratoconus, rigid gas permeable contact lenses can correct vision.

For double vision from eyes that don't line up, the American Optometric Association lists these options:

Eyeglasses, which may be the only treatment some people need
Prisms, lenses that are thicker on one side than the other. They change how light enters the eye, reduce how much the eye has to turn, and sometimes eliminate the eye turn
Vision therapy, which trains the eyes and brain to work together, in the office and at home
Eye muscle surgery, which changes the length or position of the muscles so the eyes appear straight

For convergence insufficiency, vision therapy takes the form of convergence exercises, often with a specialist and at home, and prism glasses are sometimes used.

Myasthenia gravis has no known cure, but medicines such as pyridostigmine, drugs that suppress the immune system and surgery to remove the thymus gland can reduce symptoms. When diabetes damages a nerve of the head, the symptoms usually improve with time: most people recover within a few weeks or months, even without treatment.

After a stroke, double vision costs you depth perception. An eye patch can help, though it doesn't fix the whole problem, and rehabilitation therapy can help many vision problems. Trouble moving the eyes smoothly between objects rarely gets better without therapy. Prisms can also be added to glasses to change the way you perceive objects in space.

How do we evaluate double vision at Cohenmehr Optometry?

Our optometrists in Los Angeles start by working out whether the double vision is in one eye or both. For double vision in one eye, we map the cornea with corneal topography and tomography, the shape maps used to stage keratoconus, and examine the lens with a slit lamp, a microscope for the front of the eye, using the diagnostic equipment in our office.

For an eye turn, called strabismus, care can include the right glasses, prism lenses to merge double images, vision therapy to train the eyes to work together, and co-management with a strabismus surgeon when muscle surgery is the right tool, with care before and after surgery here. Convergence insufficiency shows up on a cover test and near-point measurements in the exam room, and we treat it with doctor-directed vision therapy, sometimes with prism reading glasses.

If the exam points to a cause outside the eye, such as a nerve or blood vessel problem, we coordinate an urgent referral, and the referral and your records move the same day.

Questions patients ask

Can tired eyes cause double vision?

Tiredness can bring out an eye turn: some appear only when a person is tired, ill, or has done a lot of reading or close work, and a misaligned eye can cause double vision. Convergence insufficiency can cause tired eyes with blurry or double vision up close. Double vision or a drooping eyelid that comes and goes can signal myasthenia gravis, in which muscle weakness gets worse with activity and better with rest. Call us for an exam, the same day if an eyelid droops (an emergency room when we're closed); if double vision starts suddenly, call 911.

What is strabismus?

Strabismus is a condition in which both eyes do not look at the same place at the same time. When the eyes are misaligned, the brain receives two different images, which at first can cause double vision. In a young child, the brain learns over time to ignore the image from the turned eye, and untreated, that eye can end up with permanently reduced vision. Treatment can include eyeglasses, prisms, vision therapy or eye muscle surgery.

Can adults have a lazy eye?

Yes. Amblyopia, or lazy eye, starts in childhood, and kids who grow up without treatment may have lifelong vision problems. It develops when the brain can't recognize the sight from one eye, and strabismus, eyes that don't line up, is one of the conditions that can lead to it. Treatment is usually less effective in adults than in children. New double vision in an adult needs care right away: call 911 if it started suddenly, or call us for a same-day exam if it came on gradually (an emergency room when we're closed).

Can screen time cause double vision?

Long stretches of close work, like reading on a phone, can bring out double vision in people with convergence insufficiency, a condition that affects how the eyes work together on nearby objects. It usually starts in childhood, but it can happen at any age after a brain injury such as a concussion. Treatment includes convergence exercises and sometimes prism glasses. If the double image stays after you rest your eyes, or you also see double at a distance, get an exam; if it started suddenly, call 911.

Sources

Written by

Dr. Kevin Cohenmehr, OD

Medical eye care: glaucoma, diabetic eye exams, macular degeneration and eye infections, plus vision therapy for children. A graduate of UCLA and SUNY College of Optometry.

About Dr. Kevin →

Double Vision: What Causes It, and When Is It an Emergency?