Double Vision (Diplopia)
What Is Double Vision?
Diplopia occurs when your eyes and brain cannot work together in perfect harmony to create a single, clear image. Recognizing the type and timing of your double vision helps your eye doctor pinpoint its cause and recommend the most effective treatment.
There are two main types. Binocular double vision happens when both eyes are open and goes away when you cover either eye, which usually means your eyes are not aligned correctly. Monocular double vision affects only one eye and continues even when the other eye is covered, often signaling a problem within the affected eye itself, like a cataract.
Seeing a single, clear image requires precise teamwork. Six muscles around each eye control its movement, and these muscles are directed by signals from cranial nerves in your brain. When any part of this system, muscles, nerves, or the brain itself, is disrupted by injury or disease, the eyes can drift out of alignment, causing double vision.
Certain factors and health conditions increase your risk of developing double vision. These can include:
- Diabetes
- High blood pressure or heart disease
- Thyroid conditions, like Graves' disease
- Autoimmune disorders, such as myasthenia gravis or multiple sclerosis
- A history of head or eye trauma
Some people experience brief episodes of double vision that resolve on their own. These can be caused by extreme fatigue, stress, or alcohol consumption. However, double vision that is ongoing, comes back frequently, or gets worse over time requires a medical evaluation to find and treat the underlying cause.
Causes of Double Vision
Diplopia can arise from a wide array of conditions affecting the eyes, muscles, nerves, or brain. A comprehensive medical history and eye exam are essential for identifying the correct cause and guiding effective treatment.
When the muscles controlling eye movement are weak, imbalanced, or restricted, binocular double vision can occur. Conditions like strabismus (misaligned eyes), which can be present from birth or develop later, prevent the eyes from focusing on the same point. Thyroid eye disease can also cause eye muscles to swell and stiffen, disrupting their function.
Damage to the nerves that control eye muscles is a leading cause of double vision. This damage can result from conditions like diabetes, which can harm small blood vessels that supply the nerves. A stroke, multiple sclerosis, brain tumor, or aneurysm can also compress or damage these crucial nerves.
Since the brain processes all visual information, problems within the brain can cause diplopia. A head injury, stroke, infection like meningitis, or increased pressure inside the skull can interfere with the brain's ability to coordinate the eyes and fuse two images into one.
Monocular double vision is typically caused by issues within one eye that distort how light enters it. Common causes include cataracts, which can scatter light, significant uncorrected astigmatism, corneal scars or irregularities, and severe dry eye that affects the surface of the cornea.
Systemic diseases can manifest with double vision. Myasthenia gravis, a neuromuscular disorder, often affects eye muscles first, causing diplopia that worsens with fatigue. Side effects from certain medications, particularly those used for seizures or anxiety, can also temporarily trigger double vision.
Symptoms and When to Seek Help
Double vision is often accompanied by other signs that provide important clues to its cause. Recognizing these associated symptoms can help you determine how urgently you should seek an evaluation.
Along with seeing two images, you may experience other issues. These can include headaches, eye strain or pain with eye movement, nausea, dizziness, or problems with balance and coordination. Some people find they need to tilt their head or cover one eye to see clearly.
Seek immediate medical care if your double vision appears suddenly and is accompanied by any of the following symptoms, as they could signal a stroke or another neurological emergency:
- Sudden weakness or numbness on one side of your body
- A severe, sudden headache
- Difficulty speaking or slurred speech
- Facial drooping or a drooping eyelid
- Confusion or loss of consciousness
Persistent double vision can significantly affect your quality of life. It can make driving unsafe, turn reading into a frustrating task, and make it difficult to judge distances when walking or navigating stairs. These limitations often affect work performance and independence, making timely treatment essential.
How Doctors Diagnose Double Vision
A thorough evaluation is essential to pinpoint the cause of double vision and guide proper management. The diagnostic process is comprehensive and tailored to your specific symptoms and medical history.
Your eye doctor will perform a complete exam to check your visual acuity, pupils, and overall eye health. They will carefully test how well each eye moves in all directions and use tests like the cover test to measure how well your eyes align. This helps determine if the diplopia is monocular or binocular and which muscles or nerves might be involved.
Be prepared to discuss when the double vision started, what makes it better or worse, and any other symptoms you have. Your doctor will ask about your overall health, medications, recent illnesses, and any history of injuries. This information helps narrow down the possible causes.
If the cause is not immediately clear from the eye exam, your doctor may recommend further tests. Blood tests can check for diabetes, thyroid problems, or autoimmune conditions. Imaging tests like an MRI or CT scan may be ordered to get a detailed look at your brain, eye sockets, and the nerves controlling your eyes.
Treatment Options for Double Vision
Treatment for diplopia is aimed at correcting the double image and addressing the underlying cause. The goal is to restore single, comfortable vision, and most patients experience significant improvement with the right treatment plan.
For many people with stable, mild binocular double vision, special glasses containing prisms can be very effective. A prism is a wedge-shaped lens that bends light, helping to align the two images into a single, clear picture. These can be built into your regular prescription glasses.
In some cases, a structured program of eye exercises, known as vision therapy, can help improve the eyes' coordination and focusing ability. Alternatively, covering one eye with a patch provides immediate relief from double vision, though it reduces depth perception. Patching is often used as a temporary measure while waiting for a condition to resolve or for other treatments to work.
When double vision is caused by another health problem, treating that underlying condition is the primary goal. This might include better blood sugar control for diabetes, medication for myasthenia gravis, or treatment for a thyroid disorder. Resolving the root medical issue often eliminates the double vision.
When double vision is severe, long-standing, and not correctable with prisms, surgery on the eye muscles may be recommended. This procedure adjusts the position or tension of the muscles to improve eye alignment. Surgery has a high success rate and is typically performed as an outpatient procedure.
In certain situations, small injections of botulinum toxin (Botox) can be used to temporarily weaken an overactive eye muscle. This allows the opposing muscle to pull the eye into better alignment. The effects last for several months and can be repeated if necessary.
Frequently Asked Questions About Double Vision
Here are answers to some of the most common questions patients have about double vision.
Yes, temporary episodes caused by fatigue or minor eye strain may resolve with rest. However, any double vision that lasts for more than a few hours, comes back, or is accompanied by other symptoms should be evaluated by a doctor to rule out serious underlying causes.
Not always. It can be caused by simple issues like an outdated glasses prescription or dry eyes. However, because it can also be the first sign of a serious condition like a stroke or brain tumor, all new cases of persistent double vision should be investigated promptly by a medical professional.
Yes, children can develop double vision, often due to strabismus (crossed eyes) or uncorrected refractive errors. Children may not complain about seeing double but might show signs like squinting, closing one eye, tilting their head, or having trouble with coordination.
No, they are different symptoms. Blurry vision means objects appear out of focus or hazy, while double vision means you see two distinct images of a single object. Although they can sometimes occur together, they point to different underlying problems.
No. Binocular double vision is caused by eye misalignment and disappears when one eye is closed. Monocular double vision is caused by a problem within one eye (like a cataract) and persists even when the other eye is covered.
Eyeglasses with prisms are a very common and effective treatment for many types of binocular double vision. Specialized contact lenses can also sometimes help. However, they do not work for all cases, and other treatments may be needed.
Extreme stress and fatigue can make a pre-existing, subtle eye alignment problem more noticeable, leading to temporary episodes of double vision. While stress itself doesn't cause a permanent condition, it can worsen symptoms. Persistent double vision should always be evaluated, regardless of stress levels.
Double vision can severely impair your ability to drive safely by affecting depth perception and your ability to judge distances and the positions of other cars. It is often recommended to stop driving until your condition has been successfully treated and your vision is single and stable.
Yes, double vision can be a temporary symptom of a migraine with aura, where visual disturbances occur before or during the headache. This type of diplopia typically resolves once the migraine episode is over.
Certain medications can cause double vision as a side effect. These can include some anti-seizure drugs, tranquilizers, and even some blood pressure medications. If you suspect your medication is causing the issue, speak with your doctor; do not stop taking it without medical advice.
As people age, the risk for conditions that cause double vision, such as stroke, diabetes, and thyroid disease, increases. Additionally, the muscles and nerves that control the eyes can naturally weaken over time, sometimes leading to an alignment problem that causes diplopia.
When to See an Eye Doctor
If you experience any double vision that lasts more than a few hours, comes and goes, or is accompanied by other concerning symptoms, contact an eye care professional promptly. Early diagnosis and treatment lead to better outcomes and can protect your long-term vision and overall health.