Binocular Vision Dysfunction (BVD)

What is binocular vision dysfunction?

Binocular vision dysfunction (BVD) is when your eyes and brain don’t work together correctly. That keeps you from seeing the world as a single, seamless picture. Rather than a specific condition, it’s more like an umbrella term that can refer to many different conditions. And each of those conditions can have several possible causes of their own.

When you use both eyes to see, each eye sends a separate set of signals to your brain about what they detect. That’s where binocular vision starts. There are three grades of binocular vision:

• Macular perception. The macula is the part of your retina that sees what’s right in front of you. It’s particularly good at picking up fine details. Macular perception means both eyes can see the same thing clearly. It’s the simplest form of binocular vision.
• Fusion. This means your brain uses signals from both eyes to build two separate pictures and then “fuses” them together so the parts that overlap line up and form one big picture.
• Stereopsis. This form of binocular vision has the greatest benefits. Having this means your brain can do more than just merge the pictures. It can also use the differences in how each eye sees angles and distances, giving you 3D vision and depth perception.

How common is binocular vision dysfunction?

Many conditions fall under BVD, and while most aren’t common, a few of them are. One key example of a common form of BVD is lazy eye (amblyopia). Between 6 million and 13 million people in the U.S. have that condition.

What are the symptoms?

Your brain uses binocular vision to create or contribute to several other processes and abilities, some of which might seem unrelated to your eyes. BVD can disrupt any of those processes or abilities. Some of these effects are relatively minor and cause little or no disruption. Others are extremely disruptive, and they can even interfere with work, hobbies and more.

Pain effects

When you have BVD, your eyes and brain have to work harder to adjust and compensate. That extra effort can put a strain on eye-related muscles. It can also contribute to head and neck tension that can lead to headaches. Pain effects that can happen with, cause or contribute to BVD can include:

• Eye pain.
• Eye strain (asthenopia).
• Headaches.
• Pain from moving your eyes.

Visual effects

Visual disruptions can either cause or contribute to BVD, or happen because of it. Sometimes, it’s hard to tell when BVD is causing other issues or happening because of them. Visual effects that are possible with BVD include:

• Blurred vision.
• Double vision (diplopia).
• Light sensitivity (photophobia).
• Shadowed vision.
• Trouble focusing on objects up close.
• Trouble seeing at night (nyctalopia).
• Trouble seeing screens (computer vision syndrome).
• Trouble seeing or recognizing things that are small, faint or far away.

Nonvisual sensory effects

These revolve around other senses that vision can support. A key example is your sense of balance, which mainly comes from your inner ear. Input from your eyes can “confirm” what your inner ear’s balance-related sensors detect (and vice versa). Likewise, conflicting information can make you feel distinctly unwell. That’s why reading in the car can make some people feel severely nauseated. Nonvisual BVD effects include:

• Balance issues.
• Coordination issues (especially hand-eye coordination).
• Disorientation.
• Dizziness or lightheadedness.
• Falls.
• Motion sickness or nausea/vomiting.
• Trouble throwing or catching objects (like a ball or car keys).
• Trouble walking in a straight line or frequent collisions with objects like furniture or doorways.
• Vertigo (feeling like you’re spinning even when holding still).

Reading effects

These effects can show up when you read. In children, they can look like dyslexia or other learning disabilities. Educators with training on how to spot trouble reading often notice these issues in children. But it may still take a few different assessments to narrow down that this is BVD and not something similar. Reading effects include:

• Eye fatigue.
• Losing your place on a line or page frequently (this includes needing to use a bookmark, finger or another object to keep from losing your place).
• Needing to reread multiple times to understand fully, or trouble understanding even with multiple readthroughs.
• Skipping lines while reading.
• Trouble reading long strings of numbers (especially repeating numbers) because it’s hard to see them clearly without a punctuation mark or something else to act as a placeholder.
• Words looking like they run together.

Psychological effects

These all revolve around difficulties dealing with certain situations or environments because vision issues affect how you see them. Examples include:

• Avoiding crowds because they make you experience sensory overload or make you feel overwhelmed, anxious or afraid.
• Difficulty seeing and being in brightly lit or vividly colored environments, like supermarkets, shopping malls, retail stores, etc.
• Extreme fear of public settings or large/open places (agoraphobia).
• Feeling anxious or afraid of activities where trouble seeing might feel obvious to others or dangerous, like driving, playing sports, etc.
• Trouble maintaining eye contact in face-to-face circumstances.

What causes binocular vision dysfunction?

There are several types of factors that can cause BVD or contribute to it. Those types are:

• Sight issues.
• Eye issues.
• Brain issues.
• Multi-factor issues.

Sight issues

This type involves physical differences or distortions in how your eyes focus light onto your retinas. Examples include refractive errors like:

• Age-related difficulty focusing on close-up objects (presbyopia).
• Astigmatism.
• Farsightedness (hyperopia).
• Nearsightedness (myopia).

Eye issues

These refer to differences in how your eyes move or work together, like conditions that make your eyes misalign. Crossed eyes (strabismus) and lazy eye (amblyopia) are two of the most common examples.

Neurological issues

These are nervous system issues. They can involve issues in how certain nerves control specific muscles for eye movement, or how your retinas and optic nerves work. They can also involve issues where your brain has trouble processing visual information correctly.

The conditions that can do this vary widely. Some examples include:

• Brain-specific conditions like migraines or strokes.
• Nerve-specific conditions like sixth nerve palsy.
• Neurodivergent conditions like attention-deficit/hyperactivity disorder (ADHD).

Multi-factor binocular vision dysfunction

Some conditions don’t fit neatly into just one of the above types. Instead, they can cause multiple issues across different types.

Concussions or traumatic brain injuries (TBIs) can be an example of this. People with head injuries can have issues with eye alignment and how their brain processes visual information. Another example would be vestibular migraines, which can affect your vision, balance and brain function all at once.

People can also have multiple conditions that each contribute to BVD. An example of that would be having amblyopia since birth, and having a stroke as an adult. The two conditions happen at different points in life, but they can both contribute to BVD later on.

What are the complications of binocular vision dysfunction?

BVD can have several complications, depending on what’s causing it, when it happens in your life and other health conditions you have. Your eye care specialist is the best person to tell you about the possible complications in your case.

Binocular vision dysfunction and preventable vision loss

Lazy eye (amblyopia), a condition that falls under BVD, has one severe, permanent complication in children. Fortunately, that complication is usually preventable when caught early enough to treat.

When you have BVD, your brain has trouble merging and using input from both eyes. When that happens in children, their brains start relying on one eye more than the other. As they do, the unused eye gets weaker.

But, the vision-processing areas in a child’s brain need the right kind of input from both eyes to grow and develop correctly. If their brain stops using one eye because of amblyopia, that area of the brain can’t develop like it should. Instead, the lack of useful input damages the connections between the brain cells in that area and, eventually, that damage becomes permanent. That’s why diagnosing and treating amblyopia (especially during early childhood) is so important.

How is binocular vision dysfunction diagnosed?

An eye care specialist is usually the one to diagnose BVD. But some forms (like amblyopia) often draw the attention of pediatricians, who either diagnose it themselves or recommend an eye specialist who can diagnose and treat it.

Routine eye exams are the most useful tool for diagnosing BVD. Part of these exams includes checking your eye alignment and your overall field of vision. Other tests can also help diagnose more specific issues related to BVD. Your eye care specialist is the best person to tell you about other tests they recommend and how those tests can help.

How is binocular vision dysfunction treated?

The treatments for BVD can vary widely because so many conditions can cause or contribute to it. What works on some conditions that cause BVD won’t work on others (and the wrong treatment could make things worse).

Treatments for sight- and eye-related issues usually involve reversing or limiting any misalignment between your eyes. Some of the most common treatments include:

• Vision therapy. This involves teaching you specific exercises to strengthen your eye muscles. It also helps you learn what you shouldn’t do if you want to help your eye alignment.
• Corrective lenses and prisms. Eyeglasses (and, less commonly, contact lenses) can sometimes help with BVD. They change the way light enters your eyes, which can help with certain forms of BVD.
• OnabotulinumtoxinA (Botox®). This is a medication that blocks nerve signals to muscles that control your eye movement. This can help if your muscles pull more strongly in one direction.

Many other possible treatments exist, especially for nervous system-related BVD. Your eye care specialist can tell you about the specific treatments they recommend for you. They can also tell you the specific side effects or concerns to watch for and what you can do about them.

Can binocular vision dysfunction be prevented?

BVD isn’t 100% preventable, but there are some things you can do to prevent your risk of developing it or at least prevent it from becoming severe.

• Avoid head and eye injuries. There are several ways BVD can develop from eye or head injuries. Using proper eye protection, helmets and safety restraints (like seat belts) can help immensely.
• Get regular eye exams. Routine eye exams are like a checkup for your eyes, and even people who don’t need glasses or contacts should still get an eye exam every one to two years. These exams can detect many issues before you have symptoms, and some of the issues they can detect (like refractive errors) can also eventually cause or contribute to BVD.
• Don’t ignore eye symptoms. If you notice minor, nagging issues related to your eyes that last more than a couple of days or weeks, you shouldn’t ignore them. They can be the earliest signs of an issue like BVD. Examples include double vision, eye strain or fatigue (especially if you do a lot of reading or look at a computer screen for long periods).

If you have a family history of conditions that can cause BVD, it’s a good idea to talk to an eye care specialist about it. They can tell you about what else you can do to limit the severity of BVD, delay when it starts or even prevent it (when possible). 

What can I expect if I have binocular vision dysfunction?

What you can expect with BVD varies as widely as the conditions that can cause or contribute to it. Your eye care specialist is the best person to tell you what you can or should expect. They can also tell you how long it lasts, the outlook for your case and what you can do to help yourself manage it (if possible or necessary).

When should I see my healthcare provider or seek care?

Most of the conditions that can cause BVD can be unpleasant or disruptive, but most aren’t dangerous. Strokes and transient ischemic attacks (TIAs) are a key exception.

Strokes and TIAs are life-threatening medical emergencies. If you think you recognize the warning signs of a stroke or TIA, call 911 (or your local emergency services number) immediately. 

What questions should I ask my eye care specialist?

You may want to ask your eye care specialist the following:

• What kind of BVD do I have, or what’s causing it?
• How serious is my BVD, and can it get worse?
• Does my BVD need treatment, and if so, what treatment(s) do you recommend?
• Is BVD curable/reversible?

A note from Cleveland Clinic

Binocular vision dysfunction is usually a sign that something’s affecting how well your eyes work with each other and your brain. It means you can’t see the world as a single, seamless picture. Most of the causes aren’t dangerous — except for strokes and transient ischemic attacks (which usually happen with other highly visible symptoms).

But even when it isn’t dangerous, BVD can still make it hard to work, enjoy hobbies or spend time with loved ones. If you have the symptoms of BVD, you shouldn’t just accept them or try to tough it out. Seeing an eye care specialist can help you find treatments that reverse or even stop BVD. That way, you can live without visible disruptions standing between you and the things that matter most to you.