Binocular Vision Dysfunction (BVD): Symptoms to Know Before Testing
Binocular vision dysfunction (BVD) occurs when your eyes don’t line up, causing problems communicating with your brain. BVD can lead to double or blurred vision, light sensitivity, trouble focusing, headache, vertigo (feeling like you’re spinning), and nausea—among other symptoms.
In some cases, BVD results from congenital conditions, such as facial asymmetry (differences in the position and size of the eyes), crossed eyes (strabismus), or lazy eye (amblyopia). In others, it’s caused by age or disease-related changes in vision or the eyes, neurological disorders, or head injury.
Proper diagnosis is critical for managing BVD. Eye doctors with specialized training, such as ophthalmologists or optometrists, can diagnose the condition. However, there are ways to self-test for BVD. This article discusses the symptoms and causes of BVD, how to tell you have it, and how specialists identify and treat this condition.
Illustration by Michela Buttignol for Verywell Health
How Binocular Dysfunction Affects Vision
Binocular vision dysfunction is a wide range of problems with eye alignment. Depending on the type of BVD, these conditions affect your vision and cause other symptoms.
Types of Binocular Dysfunction
There are many ways that BVD can affect your eyes’ alignment. The most common types of BVD are:
Convergence insufficiency: This occurs when the eyes have trouble working together and focusing on objects nearby.
Convergence excess: Often arising due to problems with eye muscles, convergence excess is when one eye turns more inward than the other.
Divergence excess: The opposite of convergence excess; divergence excess occurs when one eye is turned more outward.
Amblyopia: Reduced vision in one eye makes it “lazy,” meaning it moves inward or outward while the other remains in place.
Heterophoria: This is when the eyes are out of alignment and are not being used for binocular vision. This can cause the eyes to converge (esophoria) or diverge (exophoria). Problems with vertical alignment are known as vertical heterophoria.
Strabismus: Also known as heterotopia or crossed eyes, this is when the eyes are always out of alignment. Esotropia is when they converge, and with exotropia, they diverge.
Vision Symptoms
There are a range of vision symptoms associated with BVD. These include:
Blurred vision
Difficulty changing focus from near to far
Difficulty focusing on things nearby
Difficulty seeing fine details, small objects, or things that are far away
Difficulty seeing things on screens (computer vision syndrome)
Difficulty with reading, such as words jumping
Eye strain (asthenopia)
Pain or soreness in the eye with movement
Sensitivity to light (photophobia)
Shadows or faint colors around words when reading
Skipping lines when reading
Tearing, watery eyes, excessive blinking
Tilting your head, or a book or screen
Trouble seeing in low light
Trouble with distance vision
Other Signs
BVD can also cause symptoms that aren’t directly related to vision, including:
Confusion or disorientation
Difficulty concentrating or studying
Difficulty with coordination, especially hand movements
Dizziness
Falls
Inability to walk in a straight line
Nausea or vomiting
Trouble with balance
Vertigo (feeling like you’re falling or everything’s spinning)
BVD and Mental Health
Living with a BVD can significantly impact your mental health. Studies have found those with this condition are more likely to experience psychiatric conditions, such as:
Agoraphobia (a fear of crowds or going outside)
Computer Vision Syndrome and BVD
Staring at a computer or device screen can be incredibly challenging for people with BVD. Computer vision syndrome, characterized by headaches, blurry vision, and fatigue with prolonged use, is more prevalent among those with BVD.
Binocular Vision Dysfunction Test: How to Tell
Since BVD can significantly impact your vision and cause other symptoms, proper diagnosis is crucial. If you suspect you have BVD, there are tests you can take at home before following up with an eye specialist.
To thoroughly diagnose BVD, ophthalmologists or eye specialists rely on comprehensive eye exams.
What’s Possible at Home?
At-home tests may reveal signs of a BVD, which should prompt you to get medical help. One of the most common is the five-minute cover test. Here’s how it works:
First, rate your symptoms—any visual difficulties, blurriness, headaches, and so on—between zero and 10 (with 10 being the most severe).
Cover one eye, and with the other, focus on an object in the distance for five minutes.
After five minutes, with one eye still covered, rate your symptoms again.
If symptoms improve, it’s a sign of BVD.
Some optometry or ophthalmology practices provide online questionnaires about your symptoms.
Official Diagnosis Process
Healthcare providers rely on visual acuity (how well you see) and eye alignment tests to properly diagnose a BVD. After getting a sense of your overall health, ophthalmologists or other specialists will perform the following exams:
Questionnaires: Standardized questionnaires are the typical starting point for diagnosis. You’ll answer questions about the nature and severity of your visual and other symptoms.
Comprehensive eye exam: An eye doctor will assess your ability to see nearby and far away, as well as peripheral (side) vision, and look for glaucoma or other eye disorders.
Clinical cover test: Similar to the at-home test, healthcare providers cover one eye and ask you to focus the other on objects either close by or far away and rate symptoms to assess your eyes’ alignment.
Near point convergence: Eye doctors offer this exam to evaluate how well your eyes work together when looking at objects close by.
Jump convergence: During this test, the ophthalmologist assesses how well your eyes work together when changing your focus from a distant object to a nearby object.
Prism tests: The provider may apply specialized prism lenses to correct BVD while performing near point convergence or other tests. The type of prism that corrects binocular vision problems provides a measure of how much the eyes are out of alignment.
Differential Diagnosis
Since BVD can mimic the symptoms of other conditions, it’s common for this condition to be mistaken for something else. These conditions include:
ADHD
Dyslexia
Anxiety disorders
Myasthenia gravis (an autoimmune disorder affecting muscle movement)
Benign paroxysmal positional vertigo (a disorder which causes bouts of vertigo symptoms)
Other developmental or learning disorders
Who Has Binocular Vision Dysfunction?
People of any age or health history can develop BVD. It can arise due to physical problems with the eyes, vision problems (refractive errors), neurological issues, injury, or other diseases.
Certain populations are at an increased risk of developing a BVD. Risk factors for this condition include a family history of BVD and anisometropia (issues with the eyes’ ability to refract light) and significant differences between the eyes in their ability to see.
Treatments to Correct BVD
Therapy for BVD is tailored to the individual and can involve a range of at-home and in-clinic techniques with vision specialists. These therapies often work together to ease symptoms and prevent attacks.
Office-Based Vision Therapy
Office-based vision therapy involves doing exercises to improve binocular function. In a clinic or office, you’ll be asked to perform visual tasks aimed at strengthening muscles and developing better coordination. This may involve activities like focusing on targets near and far away, and adjusting as they move.
Home Exercises
If you have been diagnosed with BVD, an ophthalmologist or eye specialist will educate you on helpful at-home eye exercises.
One approach called the pencil pushup, involves holding a pencil at arm’s length, focusing on the tip or eraser, and slowly pulling it back toward your face. The idea is to keep the image focused and change direction when the image is doubled.
Additionally, specialized computer programs can take you through exercises to develop binocular function. Studies noted that these are most effective alongside in-office treatment.
Prism Glasses
Using specialized lenses, prism glasses redirect light entering the eye to treat double-vision or other signs of BVD. Wearing these glasses and correcting other vision problems, such as near or farsightedness, can go a long way in managing these disorders.
Summary
Binocular vision dysfunction (BVD) is when your eyes are out of alignment or have trouble working together to help you see. Since BVD can cause symptoms like blurriness, double-vision, and difficulty reading, as well as headache and nausea, proper diagnosis of BVD is crucial for treatment.
Therapies for this condition include in-office vision therapy, at-home exercises, and wearing specialized prism glasses.
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