Double vision — also known as diplopia — is when a person sees two images when looking at one thing. It can come on suddenly and dramatically, or it can be more subtle, only making your vision slightly blurred. Images can appear skewed, side by side, or one above the other. 

We spoke with Carla Ericksen, O.D., an optometrist at an America’s Best Contacts & Eyeglasses in Lincoln, Nebraska. She shares what to know about the causes, symptoms, and treatment of double vision. 

Has it been a while since your last eye exam? Now’s the time to book an appointment!  

1. It Can Affect One or Both Eyes  

Double vision doesn’t always mean that both eyes aren’t seeing properly. Sometimes people can have diplopia and still see 20/20 on an eye chart. When it only affects one eye (you can close an eye and still see double), it’s called monocular diplopia. Binocular diplopia affects both eyes, and it will go away if you close one eye. 

2. Double Vision Happens More Often Than You Might Think  

It’s important to get your eyes checked right away if you have double vision, as it may be a sign of a more serious health condition. Double vision can be caused by other issues in the body and eyes.  

It happens more often than you might think. A study published in JAMA Ophthalmology found that more than 800,000 Americans seek medical help each year for double vision. Nearly 50,000 go to the emergency room because of it. 

3. People Don’t Always Realize They Have It 

Double vision sounds dramatic, but the eyesight problems it causes aren’t always obvious. “A lot of times, double vision looks like a mild shadow or a blur,” says Dr. Ericksen. Your brain and body adapt to make up for vision problems. People with double vision may make postural changes such as tilting their head or chin, turning their head, blinking, and squinting,” she says. 

 

4. Double Vision Can Come and Go  

Symptoms can seem to show up out of nowhere and go away quickly too. This is often true if your double vision is caused by a small eye muscle imbalance, Dr. Ericksen explains. Fatigue, the demands of near work, and even sickness from virus can cause intermittent symptoms. 

“Fluctuating blood sugar levels can also cause intermittent double vision,” Dr. Ericksen says. Diabetes, which happens when your blood sugar is too high, can damage the body’s circulatory system. That can paralyze the muscles that move the eyes. 

5. Monocular Diplopia Is Often Caused by Corneal Changes or Cataracts  

Cataracts are the most common reason for double vision in a single eye. They happen when your eye’s natural lens becomes cloudy. Dry eye and overwearing contact lenses can also contribute to corneal changes that can alter vision in one eye. 

“An astigmatism can also result in double vision,” Dr. Ericksen adds. Astigmatism is marked by a variation in the curvature of either the cornea or of the lens inside the eye. It is often described by patients as images appearing doubled. “With astigmatism, images often look shadowed or have a halo effect,” Dr. Ericksen says. 

6. Binocular Diplopia Can Be Caused by Your Eye Alignment  

Some people are born with eyes that don’t work together properly. “With children, often the first clue that they have diplopia is that they walk into things or have trouble at school — or simply have eyestrain,” Dr. Ericksen says.  

If parents suspect a vision problem is interfering with their child’s schoolwork or with developmental milestones such as crawling, catching a ball, or walking, they should have the child’s eye teaming skills (the ability of the eyes to work together) evaluated.  

In addition, binocular diplopia can be caused by cranial nerve issues, brain aneurysms, tumors, or even a stroke. That’s why it’s important to see your eye doctor as soon as you notice double vision symptoms. They can determine what’s causing your symptoms and get you set up with the best treatment or refer you to the right specialist, if needed.    

Recommended reading: 8 Signs Your Child Needs an Eye Exam 

7. There Are Even More Causes of Double Vision  

Beyond the reasons we’ve already explained, diplopia can also be caused by myasthenia gravis, keratoconus, Graves’ disease, thyroid disorders, certain medications, or even excessive alcohol consumption. 

“Certain medications, such as statins, anticonvulsants, antidepressants, erectile dysfunction medications, and migraine therapies have been known to cause double vision,” says Dr. Ericksen. Statins are a class of drugs that are used to lower cholesterol levels and can be overlooked as a cause of progressive weakening of the ocular musculature, she adds. 

Recommended reading: Does Your Medication Cause Eye Problems? 

8. Treatment May Be as Simple as Getting Glasses 

Your America’s Best optometrist may be able help relieve your symptoms in the meantime. First, they will evaluate you by doing a refraction, a visual field test, color vision testing, and a full ocular health evaluation.  

They will also observe how well your eye muscles move by doing a series of tests, including following objects, covering your eyes to see how they work independently, and checking depth perception by having you evaluate a depth of images while wearing 3D glasses. Depending on what they find, the optometrist might recommend corrective lenses, surgery, or vision therapy. “With vision therapy, individuals do exercises with prisms to train their nerves and muscles,” Dr. Ericksen explains.  

During the exam, be ready to answer a few questions: 

• How long have you had double vision?  
• When do you experience double vision (e.g., morning or evening)?  
• Is it constant or does it come and go? 
• Does it disappear when you cover one eye? 
• Does the image look double side by side, or does it look vertical?  
• Did you start a new medication or recently experience any trauma to your eye(s)?  
• Do you have a family history of hypertension, thyroid disease, cancer, diabetes, or immunosuppression?  

9. You Need to See a Doctor ASAP if Double Vision Comes on Suddenly 

Sudden double vision could be caused by something serious such as a stroke or an aneurysm, which is a bulge in the wall of a blood vessel.  

Sudden, constant double vision, especially when accompanied by a headache, nausea, numbness, or tingling, should be taken seriously, Dr. Ericksen explains. Call your eye doctor, your family physician, or seek emergency care. 

Don’t dismiss your symptoms — it’s important that you get checked out by an eye care professional right away. A computed tomography scan, magnetic resonance imaging, or blood work may be needed to determine the problem, she says. 

The bottom line: Double vision that comes on gradually and isn’t accompanied by other symptoms usually isn’t serious, but it should not be ignored and does warrant a call to your eye doctor to get it checked out. Double vision that comes on suddenly needs quick attention to rule out the possibility of a life-threatening condition. 

Medically reviewed by Carla Ericksen, O.D. 

See our sources: 
Diplopia diagnosis and management: Clinical Medicine 
Diabetes and double vision: American Academy of Ophthalmology 
Children and diplopia: Journal of American Association for Pediatric Ophthalmology and Strabismus