What Is Binocular Vision Dysfunction (BVD)?

Binocular vision dysfunction (BVD) is an umbrella term for conditions in which the two eyes do not work together properly. Normal binocular vision requires the two eyes to send visual signals to the brain, and then for the brain to merge the two images together into a single stable picture.

Binocular vision dysfunction is not simply blurry or low vision requiring an increased prescription via glasses or contact lenses. Patients can have perfect 20/20 vision on a routine exam but still experience significant symptoms due to eye misalignment and poor teaming/focusing behavior. 

Since the brain works to prevent double vision, even subtle misalignment can make the visual system work harder to maintain clear, single, stable vision. To diagnose subtle problems in eye teaming, a binocular vision test is needed rather than just testing visual acuity.

Symptoms of BVD

Symptoms of binocular vision dysfunction can occur when the visual system has to work harder than usual to maintain clear, single, comfortable vision. Symptoms of BVD often fall into three broad functional categories: visual symptoms, headaches/dizziness/balance symptoms, and reading/concentration difficulties.

Visual Symptoms

The most obvious symptoms related to BVD are around the eyes themselves. Common complaints include blurry vision, double or diplopic vision, inability to focus properly, and significant eye strain or fatigue. Many patients report light sensitivity to fluorescent lighting and discomfort with prolonged screen use or close reading.

Headaches, Dizziness, and Balance Symptoms

When visual alignment is difficult to maintain, some patients may compensate with posture changes during visually demanding tasks. Thus, the symptoms that arise are physical/vestibular in nature. Common complaints include migraine-like symptoms, headaches, eye strain, and sometimes neck or shoulder tension from compensating posture during reading, screen use, or driving. Vision plays an important role in the body’s sense of spatial awareness, and visual mismatch may contribute to dizziness and visual disorientation, causing severe motion sickness and nausea, particularly in visually stimulating environments like grocery stores.

Reading/Concentration

Reading requires sustained coordination of eye movement. BVD leads to difficulty with reading and subsequently eye strain fatigue. Patients skip lines, reread continuously, and lose their place. The cognitive strain results in short attention span, difficulty concentrating during school or work activities, and eventually avoidance of near work or screen use altogether. Children and adults may also experience anxiety or discomfort in crowded spaces, busy grocery stores, or while driving because visually complex environments can feel overwhelming.

Why BVD Is Confused With Other Diagnoses

The symptoms of BVD can often cloud the diagnosis because they overlap with many other medical, neurological, vestibular, and learning-related conditions. Patients with symptoms consistent with BVD are often initially worked up for:

• Migraine and eye strain
• Vertigo and vestibular disorders
• Anxiety
• ADHD or dyslexia
• Post-concussion and motion sickness

This does not imply that these things cannot coexist, but that unaddressed eye alignment or poor eye teaming can contribute to symptoms that appear similar. For example, visual-vestibular mismatch related to BVD can contribute to dizziness and visual discomfort, often associated with generalized anxiety disorder. If persistent symptoms exist despite a normal standard eye exam, or effective treatment for other medical causes fails, then a specialized binocular vision evaluation should be considered.

Causes of BVD

BVD is caused by a variety of underlying developmental, pathological, and neurological conditions that adversely affect eye alignment, focusing, and movement. These include factors such as amblyopia and eye alignment issues secondary to strabismus from developmental origins. Mechanical imbalances like convergence insufficiency, vertical and horizontal heterophoria, as well as neurological trauma from concussion, TBI, or stroke that disrupts visual pathways, are key contributors. Increased demand from reading, scrolling, and screen use exacerbate symptoms but do not directly cause the anatomical issues.

How Is BVD Diagnosed?

Standard eye exams primarily focus on visual acuity and often miss functional coordination issues. Specialized binocular vision testing is required. Diagnosis starts with a detailed symptom history and questionnaire, evaluating when and where symptoms occur. The exam includes standard visual acuity and eye health assessments, combined with functional tests like:

• Eye alignment and cover/uncover testing
• Near point convergence to test eye teaming on close objects
• Assessment of vergence and focusing flexibility
• Depth perception (stereopsis) evaluation
• Prism lens trials to assess symptom relief

Diagnosis is based on the presence of symptoms, objective clinic testing findings, and responses to corrective interventions such as prism lenses.

When to Test for BVD

Testing is warranted when persistent unexplained symptoms negatively impact quality of life despite a normal routine eye exam. If symptoms such as headaches, dizziness, or reading difficulties continue even after a standard checkup, a specialized binocular vision evaluation, including a test for BVD, may help identify subtle eye-teaming problems.

Comprehensive screening is appropriate in cases of:

• Headaches triggered by reading, driving, or computer use
• Dizziness/nausea in visually complex environments like stores
• Persistent eye strain not alleviated by rest or glasses
• Reading difficulties with avoidance of near work despite normal visual acuity
• Unexpected motion sickness or double/intermittent blurred vision
• Post-concussion symptoms
• Children avoiding schoolwork or showing frustration with near-vision tasks

If these symptoms persist despite other treatments, a BVD test may uncover subtle misalignments missed by routine exams.

Treatment and Management

Treatment for BVD and related eye-teaming issues usually focuses on reducing visual strain, improving eye coordination, and supporting comfortable vision. Specialized prism lenses may reduce visual strain by helping the eyes maintain more comfortable alignment, decreasing the effort needed to maintain clear, single vision. Environmental modifications to the screen and workstation setups, along with periodic breaks during reading, help manage symptoms. Vision therapy aims to retrain coordination and focusing. Follow-up testing and co-management of neurological conditions often accompany treatment.

Summary Takeaways

• BVD impacts comfort, dizziness, balance, reading, driving, and concentration.
• Symptoms include head/eye/neck pain, dizziness, and motion sensitivity.
• Related to but often confused with migraine, vertigo, anxiety, ADHD, and dyslexia.
• Specialized testing identifies the underlying connection.
• Treatment includes prism lenses and vision therapy.

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