9 Things to Know About Double Vision

Seeing double can be a scary thing, especially if it occurs suddenly. Sometimes, double vision (official name: diplopia) has relatively minor, fixable causes, such as too much digital screen time or having astigmatism (which glasses or contacts can correct). However, double vision can also be a sign of significant medical problems and should not be ignored. Learn more about this common vision problem, including its causes, treatments and when to seek medical help.

Double vision may occur in only one eye or in both. If you are seeing double, try covering each eye in turn. If your double vision clears up when looking out of each eye on its own, but reappears when both are uncovered, you have binocular diplopia—that is, double vision in both eyes. Double vision in only one eye is called monocular diplopia. The types of double vision have different causes. Also, your double vision may appear with images beside each other (horizontal), on top of the other (vertical), or separated diagonally from each other (oblique).

If you have monocular double vision, it’s likely there is something going wrong in the eye itself. If your double vision is in both eyes, the cause is more likely related to eye muscle, nerve or brain issues. Some potential causes:

• Astigmatism, blurry vision caused by an irregularly shaped cornea or lens
• Dry eyes
• Infections, such as shingles
• Scars from disease, infection or injury
• Cataract, when your lens clouds up as you age
• Retinal disease
• Orbital inflammation as occurs in thyroid eye disease
• Multiple sclerosis
• Orbital cysts and tumors

These problems are largely fixable. Your eye doctor can explore options for you, such as surgery, medication or corrective lenses.

Muscles in your eye socket control how your eyes move. If they become weak or paralyzed, your eyes may not move in sync with each other, causing double vision. Children sometimes are born or develop an eye muscle imbalance called strabismus (crossed eyes) and result in double vision. Infants won’t complain about their double vision and that can result in vision loss due to amblyopia (lazy eye). When caught early, an ophthalmologist (eye surgeon) can correct strabismus. Another reason for eye muscle problems is the thyroid condition Graves’ disease. Medication or surgery can usually resolve thyroid-related double vision.

When nerves that connect your brain and eye muscles are damaged, you may experience double vision. The most common acquired condition is palsy of the trochlear nerve; this is often related to head trauma. Other conditions that can cause this abnormality include diabetes, cerebral stroke, Guillain-Barré syndrome, myasthenia gravis, and multiple sclerosis.

Problems inside the brain, due to illness or injury, could be the root cause of your double vision. They include migraine, brain aneurysm, stroke, pressure inside the brain, and brain tumor.

Neurologists typically treat migraine headaches with medication. Other brain conditions, such as an aneurysm or stroke require immediate, emergency medical care, and may require surgery. If you have sudden double vision that lasts two hours, call your primary care or eye doctor or go to the closest emergency room. More gradual double vision should also be brought to your doctor’s attention.

Computer vision syndrome is an increasingly common problem with so many of us staring at digital screens on computers, laptops, tablets and smartphones. This can lead to blurred vision, dry eyes and, sometimes, double vision. To remedy this, try resting your eyes every 20 minutes by looking 20 feet away from your device for at least 20 seconds. Also, for every two hours of computer time, rest your eyes for 15 minutes. Remember to blink often and, if needed, use lubricating eye drops.

When your eye doctor examines you for double vision, he or she will evaluate your overall vision and eye health and perform other tests based on your symptoms. Your doctor will want to find out if your diplopia:

• is in one eye or both
• is constant or occasional
• came on suddenly or gradually
• affects only far or near vision
• changes when you move your head or gaze

Besides an exam, you also may need imaging, such as an MRI or CT scan, and blood tests, depending on your symptoms.

Some websites and apps allow you to take vision tests, usually to determine how well you see (visual acuity). The American Academy of Ophthalmology and American Optometric Association both have warned that online tests aren’t a replacement for in-person exams, because they can’t detect serious eye problems or underlying health conditions. The associations say people aged 18 to 39 who do not need glasses may use such tests. However, they advise anybody who has vision problems (such as double vision), as well as those younger than 18 or older than 39 see an eye professional, and do so in person.

Your double vision treatment will depend on what’s causing it. An accurate diagnosis will guide treatment decisions. Some people get injections of Botox (botulinum toxin) in the opposing eye muscle to prevent further tightening of that stronger eye muscle. In a stroke patient, the paralyzed muscle may not fully recover after an acute palsy. Left untreated, the healthy opposing eye muscle will progressively tighten and make double vision worse. In this situation, weakening the stronger, functioning eye muscle with injections of Botox can help restore some balance. Botox needs to be repeated several times to achieve a good result.

Small amounts of diplopia may be managed with prism spectacles. Eye patches or special lenses in your contacts or glasses can block vision in one eye, which can eliminate double vision. Surgery may be necessary for some causes of double vision.

If your double vision is related to computer eye syndrome, you may need to learn how to rest and refocus your eyes periodically, along with such measures as getting special lenses or computer screen filters to minimize glare.