Binocular Vision Dysfunction

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When the eyes struggle to work together, it leads to a condition called Binocular Vision Dysfunction (BVD). BVD can cause frustrating visual symptoms that disrupt daily life. 

This article covers what BVD is, the common symptoms it causes, how it can sometimes be misdiagnosed, proper diagnosis methods, effective treatment options, etc.

Gain a better understanding of this complex vision condition and the available treatments that provide relief.

What is Binocular Vision Dysfunction?

Binocular Vision Dysfunction (BVD) is a common vision condition affecting about 15-20% of the population. Our eyes work together as an effective team to send the brain one clear unified visual image.

When there is weak eye teaming, a misalignment of the eyes, known as strabismus or heterophoria, it causes difficulties for the eyes to point exactly in the same angle/direction when focusing on an object. As a result, the brain receives two slightly different images from each eye rather than one clear combined image.

This confuses the brain, disrupts depth perception, and causes various symptoms. BVD symptoms can cause visual performance to drop across the day and it can also get progressively worse over time without treatment. This visual condition can significantly impact school, work, daily activities, and quality of life.

Common Symptoms of BVD

BVD can cause a wide variety of symptoms that impair daily functioning.

Common visual signs and symptoms include:

  • Complains of blur vision

  • Parents observe one eye moving in or out, eyeturn or squint

  • Blinking frequently

  • Certain lightings cause discomfort

  • Skips words/lines when reading

  • Uses finger to keep place when reading

  • Closes or covers one eye

  • Occasionally sees double, “words moving”

  • Holds things very close

  • Eyes are tired or strained

  • Able to read for only a short time

  • Has headaches when/after reading

  • Poorer sustained near attention

  • Difficulties copying from board

Physical adaptations or signs associated with BVD:

  • Abnormal working posture
  • Neck, shoulder, and back pain
  • Head Tilt
  • Motion sickness
  • Dizziness

Difficulties reading symptoms related to BVD include:

  • Difficulty with attention and concentration
  • Easily fatigued while reading
  • Seeing words appear to float or move on pages and screens
  • Skips words and lines during reading causing poor comprehension

BVD Can Be Misdiagnosed As Other Conditions

Because the symptoms of BVD often mimic other conditions, it is commonly mistaken for:

  • Dyslexia – Reading struggles can sometimes be misattributed to dyslexia rather than impaired visual processing from BVD. However, a child can have both BVD and Dyslexia as well.
  • Migraines – Headaches are considered migraines when they are caused by BVD-related eye strain.
  • Refractive error problems – BVD symptoms are mistaken for a increase in eye power rather than the binocular dysfunction causing them.

How is BVD Diagnosed?

An optometrist will conduct a series of comprehensive eye exams and vision tests to diagnose BVD. These assessments are designed to identify the specific dysfunction in binocular vision causing the symptoms. Tests may include:

  • Eye misalignment evaluation – To check for strabismus or eye-turning, which reveals problems with eye muscle control.
  • Stereoacuity test – Measures 3D depth perception, which relies on proper eye alignment.
  • Convergence insufficiency testing – Assesses how well eyes work together for near focus.
  • Eye movement exams – Check smooth coordination between eyes when tracking objects.
  • Vision acuity test – Measures clarity of vision, focus, and eye chart reading at near and far distances.
  • Refraction test – Determines the need for corrective lenses to improve overall focus.

Effective Treatment Options for BVD

After diagnosis, the treatments for BVD are:

  • Prescription glasses or contact lens – Prescription eyeglasses or contacts lens, that may have customised reading addition, or specialised calculated front curves and base curves to equalise disparate image sizes between both eyes.
  • Prism Lens – The prescription may also include prismatic components to redirect light to compensate for the weak visual posture or the eye misalignment to allow immediate symptom relief in most cases.
  • Vision therapy – Individualized training, exercises, and activities are prescribed to improve the fluency of eye tracking, the amplitudes for eye teaming (convergence, divergence) and eye focusing. This retrains the visual system for better alignment and teamwork between the eyes, ultimately for better visual comfort.

Some patients may require prism lenses and vision therapy together to reduce their initial visual symptoms to improve functioning in their work. Treatment plans are tailored to each patient as there are variations of binocular vision dysfunctions.

Vision Therapy for BVD

Vision therapy is a structured treatment process that utilizes skilled therapists, specialized equipment, and a carefully planned progression of activities to modify the visual system at the neurological level.

Contrary to certain beliefs, it’s essential to clarify that Vision therapy does not remove the need for glasses or promise the attainment of perfect eyesight. The main cause of myopia is the elongation of the eyeball.

Engaging in Vision therapy does not reduce the length of the eye, and as a result, achieving perfect eyesight through Vision therapy is not feasible.

The focus of vision therapy is on enhancing visual motor abilities, encompassing improvements in the speed, accuracy, amplitudes, flexibility, and endurance of the visual system’s motor functions.

This includes working on oculomotor skills (eye tracking), divergence/convergence abilities (eye teaming), and accommodative ability (eye focusing).

Establishing a strong visual motor system serves as a crucial prerequisite, enabling the development of higher cognitive learning skills such as visual perceptual abilities, processing speed, and proficiency in reading and writing.