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Binocular vision and binocular vision dysfunction

illustration of binocular vision and the brain

What is binocular vision?

Binocular vision describes the way the two eyes work together to integrate images seen by each eye into one image. (If you break down the word, “bi” means “two,” and “ocular” means “eyes.”)

Both the left and right eye have their own line of vision. In functional binocular vision, these two pathways fuse together to create a single, clear image. The process also provides for a wide field of vision and precise depth perception.

How does binocular vision work?

In binocular (two-eyed) vision, each eye sees an object from a varying angle. This information is then sent to the brain, which compares and processes the different images into one single image. When a complete, single image is projected in front of you through this eye-to-brain communication, it is referred to as stereopsis (depth perception)

Some people struggle with depth perception and eye alignment, which can interfere with achieving stereopsis. This may result in eye coordination problems and conditions such as:

SEE RELATED: What part of the brain controls vision? 

Binocular vision dysfunction (BVD)

When the eyes don’t work together as a team, it is hard for the brain and visual system to produce a single, clear image. This type of error is called binocular vision dysfunction (BVD), and it involves either a vertical or horizontal misalignment in the eyes.

Some examples of common binocular vision problems include:

  • Horizontal strabismus, such as esotropia (inward eye turn) or exotropia (outward eye turn).

  • Vertical strabismus, such as hypertropia (upward eye turn) or hypotropia (downward eye turn).

  • Convergence insufficiency, in which the eyes tend to point outward during near work.

  • Convergence excess, in which the eyes tend to point inward during near work.

The misalignment associated with BVD may be very obvious or it may be very subtle. The testing process for binocular vision dysfunction is very detailed and sensitive in order to properly identify issues and determine a proper treatment plan.

SEE RELATED: Eye exams for children: Why they're important

Symptoms of binocular vision dysfunction (BVD)

BVD can present with several different symptoms — some of which are not associated with vision. Many people with BVD also struggle with symptoms related to reading, driving, balance and mental health.

Be sure to take note if you experience one or more of the following:

  • Blurred vision

  • Double vision

  • Eye strain (asthenopia)

  • Visual symptoms that worsen at the end of the day

  • Headaches 

  • Eyes turning inward or outward

  • Difficulty reading and writing, as words may seem to “swim” around the page

  • Feeling of fatigue during or after near work

  • Dizziness

  • Nausea

  • Vertigo

  • Light sensitivity

  • Trouble focusing while driving, as some stationary objects may appear to be moving

Binocular vision disorder and ADHD

Experts have discovered that BVD may present with similar symptoms to attention deficit hyperactivity disorder (ADHD). A child whose eyes are misaligned may have trouble concentrating, reading and writing because it is physically difficult for them to do so. In school classrooms, excess visual stimulation can be more of a distraction than an enhancement to their education. 

Adults may also struggle with similar symptoms while at work, driving or in various public spaces.

Since the symptoms of BVD and ADHD are so closely related, it’s important to have an eye exam to investigate the function of your binocular vision. A pair of glasses or additional treatments could make all the difference if the problem is vision-related. (And don’t hesitate to also consult your primary care physician about ADHD symptoms.)

SEE RELATED: ​​Vision problems can be misdiagnosed as ADHD or ADD 

Causes of binocular vision dysfunction (BVD)

There are a few main causes of BVD, including:

  • Environmental stress on the visual system

  • Trauma and traumatic brain injury (TBI), such as a stroke or concussion

  • Errors in vision development

  • Congenital causes

Diagnosis and treatment for binocular vision dysfunction (BVD)

Before beginning treatment for BVD, your eye doctor will evaluate your entire visual system. The first step in any vision treatment is to correct refractive error. If a refractive error such as myopia (nearsightedness), hyperopia (farsightedness) or astigmatism is present, glasses or contact lenses will be prescribed as the initial treatment. 

The eyes are checked very carefully as misalignment associated with BVD may be very obvious or very subtle. 

The treatment options for BVD include: 

Every treatment has the goal of getting the eyes to work together in a more efficient manner and maintaining single, clear vision. 

Monitor your vision with regular eye exams

It’s important to schedule a comprehensive eye exam once a year to keep every aspect of your vision healthy and functional — including binocular vision. 

If you notice any changes in your focusing abilities, have trouble reading or driving, or if you experience any other symptoms that could point to a problem with your binocular vision, contact your eye doctor immediately.

READ NEXT: Visual perception: How it works & common disorders

Binocular vision. University of Iowa Health Care. January 2013.

Depth perception. American Academy of Ophthalmology. March 2018.

Binocular vision correction. The Vestibular Disorders Association. Accessed July 2022.

Testing children for accommodative and convergence disorders. Review of Optometry. October 2017.

What is vertical heterophoria? Neurovisual Center of New York. Accessed July 2022.

Bringing the symptoms of binocular vision dysfunction into focus. Neurovisual Center of New York. Accessed July 2022.

Treatment of vertical heterophoria ameliorates persistent post-concussive symptoms: A retrospective analysis utilizing a multi-faceted assessment battery. Brain Injury. February 2016.

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