Do you sometimes get headaches? Or do you feel like the lines of text are jumping or you see two things at once when reading a book or newspaper? Or do your eyes sometimes feel tired and heavy? One reason for these things could be a slight problem with the coordination between your eyes and your brain. We are going to talk about such a condition today. It is called binocular vision dysfunction, or as doctors call it `(Binocular Vision Dysfunction - BVD)`.
What is Binocular Vision Dysfunction?
Simply put, Binocular Vision Dysfunction (BVD) is when your eyes and your brain don't work together properly. When this happens, we don't see the world as a single, clear picture. It's not a single disease, it's like an umbrella. There can be a number of different conditions under that umbrella. Each of those conditions can have their own unique causes.
When we look with both eyes, one eye sends a few different signals to the brain, and the other eye sends a few different signals. That's where binocular vision begins. There are three main levels of binocular vision:
1. Macular perception : In the center of the retina inside your eye is a part called the macula . This is what allows us to see things in front of us, especially fine details. Macular perception means that both eyes can see the same thing clearly. This is the simplest level of binocular vision.
2. Fusion : This is where your brain uses signals from both eyes to create two separate images, then "merges" them, putting the matching parts together to create one larger image. Think of it like pasting two pictures together.
3. Stereopsis : This is the most advanced level of binocular vision. This means that your brain can do more than just add the two images together. It uses the small differences in the angles and distances that your eyes see things from to give you 3D vision and depth perception . This is how we know exactly how far away something is and how deep it is.
How common is this `(BVD)` condition?
There are many conditions under the umbrella term ``BVD''. While many are not very common, some are quite common. One prime example is ``lazy eye'' or, in medical terms, ``amblyopia'' . In the United States alone, between 6 and 13 million people suffer from this condition. There are people with this condition in Sri Lanka as well.
What are the symptoms of `(BVD)`?
Your brain uses binocular vision to create or support a number of other processes and abilities. Some of them may seem unrelated to the eyes, but BVD can disrupt any of these processes. Some of the effects are minor, so they don't cause much of a problem. But others can be very disruptive, sometimes interfering with your work or hobbies.
Pain-related effects
When you have BVD, your eyes and brain have to work harder to adjust and compensate for the loss. This extra strain can cause the muscles around your eyes to become strained. This can also cause stiffness in your head and neck, which can lead to headaches . Painful conditions that can occur with BVD include:
- Eye pain.
- Eyestrain (asthenopia).
- Headache.
- Pain when moving the eyes.
Vision-related effects
Vision problems can be caused by BVD or caused by BVD. Sometimes it is difficult to tell whether other problems are caused by BVD or whether other problems are causing BVD. Vision problems that can occur with BVD include:
- Blurred vision, unclear vision.
- Seeing two things at once (diplopia) .
- Sensitivity to light (photophobia).
- Seeing things clearly as if they were surrounded by shadows.
- Difficulty seeing (focusing) close-up objects clearly.
- Reduced vision at night (`nyctalopia`).
- Difficulty looking at computer screens and phone screens (`computer vision syndrome`).
- Difficulty seeing or recognizing small, unclear, or distant objects.
Other effects that are not related to vision, but are felt
These are related to other senses, but vision helps with this. A good example is your body's balance . This comes mainly from your inner ear. But the information from your eyes also helps the balance sensors in your ear. For example, if you're reading a book while driving, some people feel like vomiting because of the imbalance. Here are some of the effects that can occur with BVD:
- Problems with body balance.
- Coordination problems (especially hand-eye coordination). For example, having difficulty catching a ball or throwing a key.
- Feeling confused (Disorientation).
- Dizziness or feeling light-headed.
- About to fall.
- Nausea and vomiting when traveling (motion sickness).
- Difficulty walking in a straight line, frequent bumping into furniture and doors.
- Feeling like you are spinning even when you are standing still (vertigo).
Effects related to reading
These effects can occur when you read. In children, this can look like a learning disability like dyslexia. Teachers who are trained to identify reading difficulties can see these in children. But to find out for sure if this is due to BVD or something else, you need to do a number of different tests. Effects on reading:
- Feeling tired in the eyes.
- Frequently skipping lines or pages while reading (this includes having to read with something like a bookmark or finger).
- Having to read it several times to understand it properly, and even then it's hard to understand.
- Making way for the lines when reading.
- A long string of numbers (especially one with the same number repeated) is difficult to read, because it is not clearly visible without a mark like a comma.
- The words seem to be stuck together.
Psychological effects
All of this happens because vision problems make it difficult for you to deal with certain situations or environments. Examples:
- Avoiding crowded places, because then you will experience sensory overload and feel burdened, anxious, and afraid.
- Difficulty staying in brightly lit, brightly colored environments, such as supermarkets and shopping malls.
- An abnormal fear of public places or large/open spaces (`agoraphobia`).
- Feeling afraid or anxious about activities that may be visible to others, such as driving or playing sports, or that may be dangerous.
- Difficulty making eye contact when talking face to face.
Why does this `(BVD)` occur?
There are several types of factors that can cause or contribute to BVD:
- Sight problems.
- Eye problems.
- Brain problems.
- Problems caused by the combination of several factors (multi-factor).
Sight problems
This type includes physical changes or distortions in the way your eyes focus light onto the retina. For example, refractive errors:
- Difficulty seeing near as you age (presbyopia).
- Astigmatism.
- Farsightedness (far objects are clear, near objects are blurry - `hyperopia`).
- Short-sightedness (near objects are clear, distant objects are blurry - `myopia`).
Eye problems
These refer to changes in the way your eyes move or work together. For example, conditions where the eyes are not aligned properly. Strabismus (crossed eyes) and amblyopia (lazy eye) are two common examples of this.
Neurological problems
These are problems with the nervous system. They can include problems with the functioning of some of the nerves that control eye movement, or problems with the way your retina and optic nerves work. They can also include problems with your brain not being able to process the information it receives from your vision properly.
There are many different situations that can cause this. Some examples:
- Brain-specific conditions, for example migraines or strokes.
- Nerve-specific conditions, for example, sixth nerve palsy.
- Neurological conditions, for example, Attention-Deficit/Hyperactivity Disorder (ADHD).
BVD is caused by a combination of several factors.
Some situations cannot be put into just one of the above categories. Instead, they can cause several different types of problems.
Head injuries, especially those to the brain (concussions or traumatic brain injuries - TBIs), are an example of this. People who have had head injuries can have problems with eye alignment and the way the brain processes information from vision. Another example is vestibular migraines. These can suddenly affect your vision, balance, and brain function.
Also, a person can have several conditions that contribute to BVD. For example, someone who is born with amblyopia (lazy eye) may have a stroke in adulthood. Although these two conditions occur at different times in life, both can cause BVD later in life.
What are the possible complications of `(BVD)`?
There are several complications that can occur with BVD. It depends on what caused it, when in your life it occurred, and what other health conditions you have. Your eye doctor is the best person to tell you about the possible complications related to your condition.
`(BVD)` and preventable vision loss
Children can develop a serious, permanent complication called "lazy eye" (amblyopia), which falls under the category of "BVD." Fortunately, this complication is usually preventable if it is recognized early enough for treatment.
When you have BVD, your brain has difficulty integrating and using information from both eyes. When this happens to children, their brains start to rely more on one eye than the other. When this happens, the eye that is not being used becomes weaker.
However, for the areas of a child's brain that process vision to develop properly, they need to receive the right information from both eyes. If they stop using one eye because of amblyopia, that area of the brain won't develop properly. Instead, the lack of useful information damages the connections between brain cells in that area, which eventually becomes permanent. That's why it's so important to identify and treat amblyopia, especially at an early age.
How is this `(BVD)` condition diagnosed?
BVD is usually diagnosed by an ophthalmologist. However, some conditions, such as amblyopia, are brought to the attention of pediatricians. They either diagnose it themselves or refer you to an ophthalmologist who can diagnose and treat it.
Routine eye exams are the most helpful way to diagnose BVD. As part of these exams, your eyes' alignment and your overall field of vision are checked. Other tests can help identify specific problems related to BVD. Your eye doctor is the best person to tell you what other tests they recommend and how they can help.
How is BVD treated?
Treatments for `(BVD)` can vary greatly, as there are many conditions that can cause or contribute to it. What works for some conditions that cause `(BVD)` may not work for others (and the wrong treatment can even make the condition worse).
Treatments for vision and eye problems usually aim to correct or limit the misalignment between your eyes. Some of the most common treatments include:
- Vision therapy : This will teach you specific exercises to strengthen your eye muscles. You will also learn what not to do to help your eyes stay in place.
- Corrective lenses and prisms : Sometimes glasses (and, less commonly, contact lenses) can help with BVD. They change the way light enters the eye, which can help some forms of BVD.
- OnabotulinumtoxinA (Botox®) : This is a medication that blocks nerve signals to the muscles that control your eye movement. This can help if your muscles twitch too much on one side.
There are many other treatments, especially for neurological diseases (BVD). Your eye specialist can tell you which treatments are recommended for you. They can also tell you what side effects or concerns you may have with those treatments, and what you can do about them.
What can I expect if I have `(BVD)`?
What you can expect when you have BVD is as varied as the conditions that can cause or contribute to it. Your eye doctor is the best person to tell you what you can or should expect. They can also tell you how long it will last, what the outlook is for your condition, and what you can do to help manage it (if possible or necessary).
Can BVD be prevented?
BVD cannot be prevented 100%. But there are a few things you can do to reduce the risk of it occurring, or at least prevent it from getting worse.
- Prevent head and eye injuries : There are several ways to prevent BVD from occurring due to injuries to the eyes or head. Wearing eye protection, helmets, and safety harnesses (such as seat belts) can help a lot.
- Get regular eye exams : Regular eye exams are like a check-up for your eyes. Even those who don't need glasses or contact lenses should have an eye exam at least twice a year. These exams can detect many problems before you have symptoms. Also, some of the problems they detect (like refractive errors) can eventually cause or contribute to BVD.
- Don't ignore eye symptoms : If you have minor, bothersome eye problems that have been going on for a few days or weeks, don't ignore them. They could be the first signs of a problem like BVD. For example, seeing double, eyestrain, or fatigue (especially if you read a lot or stare at a computer screen for a long time).
If anyone in your family has conditions that can cause BVD, it's a good idea to talk to an eye specialist about it. They can tell you what else you can do to limit the severity of BVD, delay its onset, or (if possible) even prevent it.
When should I see my doctor or seek medical advice?
Many conditions that can cause ``BVD'' can be uncomfortable or disruptive, but most are not dangerous. However, strokes and transient ischemic attacks (TIAs) are special cases and can be life-threatening.
Strokes and transient ischemic attacks (TIAs) are life-threatening medical emergencies. If you think you may be experiencing the warning signs of a stroke or TIA, call 911 (or your local emergency number) immediately.
What questions should I ask my ophthalmologist?
You may want to ask your eye specialist these questions:
- What kind of `(BVD)` condition do I have, or what is causing it?
- How serious is my `(BVD)` condition, and could it get worse?
- Does my `(BVD)` condition require treatment? If so, what treatments do you recommend?
- Can `(BVD)` be cured/reversed?
Take-Home Message
Binocular Vision Dysfunction (BVD) is a sign that something is affecting how well your eyes work together and with your brain. It means you don't see the world as a single, clear picture. Most causes are not serious - except for strokes and transient ischemic attacks (TIAs) (which usually occur with other obvious symptoms).
But, even though it's not dangerous, BVD can make it difficult to work, enjoy hobbies, or spend time with loved ones. If you have symptoms of BVD, don't just accept them or try to live with them. Seeing an eye specialist can help you find treatments that can reverse or stop BVD. Then you can live your life without your vision getting in the way of the things that matter to you and your loved ones.
` Binocular vision dysfunction, BVD, vision problems, double vision, lazy eye, amblyopia, eyestrain, headaches, blurred vision
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