Binocular Vision Dysfunction

Binocular Vision Dysfunction (BVD) occurs when the two eyes have difficulty working together accurately and comfortably as a team.

This can affect eye coordination, focusing and tracking, and may cause symptoms during reading, computer use, driving or other everyday visual tasks.

Common Symptoms of Binocular Vision Dysfunction

You may experience:

headaches or tired eyes, particularly after reading or close work;
blurred or intermittent vision;
double vision;
difficulty keeping words clear while reading;
words appearing to move or overlap;
losing your place or skipping lines;
difficulty changing focus between near and distant objects;
closing one eye to see more comfortably;
difficulty maintaining concentration during visually demanding tasks.

Symptoms can vary depending on which visual skill is affected.

Eye Teaming - Vergence

Eye teaming refers to the ability of both eyes to move inward and outward together so they remain accurately aligned on an object.

When this system is not working effectively, conditions may include:

Convergence Insufficiency - the eyes are unable to cross together when looking at a near object and begin to drift outwards. Here the brain perceives the object to be further away than it actually is.
Convergence Excess - the eyes cross too much when trying to look at a near object. Here the brain perceives the object to be closer than it actually is.
Divergence Insufficiency - the eyes are unable to relax and move outward together to look at something in the distance. The brain perceives the object to be closer than it actually is.
Divergence Excess - the eyes relax and move outwards too much when looking in the distance. The brain perceives the object as being further away than it actually is.

Double vision, eye strain and difficulty sustaining near work may occur when eye teaming is not functioning effectively.

Eye Focusing - Accommodation

Accommodation is the ability of the eyes to adjust focus so objects remain clear at different distances.

Focusing difficulties may include:

Accommodative Insufficiency – reduced focusing ability for near tasks;
Accommodative Fatigue – focusing may initially be normal but becomes difficult to sustain over time;
Accommodative Infacility – difficulty changing focus quickly between near and distant objects.

Symptoms may include intermittent blurred vision, difficulty maintaining clarity when reading or blurred distance vision after prolonged close work.

Focusing ability naturally reduces with age. From around the age of 40, this gradual loss of near focusing ability is known as presbyopia and is usually managed with reading or multifocal glasses.

Eye Tracking - Ocular Motility

Eye tracking refers to the ability to move the eyes accurately and efficiently between objects or along a line of text.

Important eye movement skills include:

Fixation – keeping the eyes steadily focused on a target;
Saccades – making quick, accurate eye movements between targets;
Pursuits – smoothly following a moving object.

Difficulties with eye tracking may contribute to:

losing your place while reading;
skipping or rereading words and lines;
relying heavily on a finger or ruler to keep your place;
excessive head movement during reading or desk work.

How Is Binocular Vision Dysfunction Assessed?

A standard eyesight test measures how clearly each eye can see, but it may not identify difficulties with the way the eyes work together.

An Orthoptic Assessment, also known as a Binocular Vision Assessment, examines eye alignment, focusing, eye teaming and eye movement skills to determine whether a binocular vision problem is present.

How Is Binocular Vision Dysfunction Treated?

Treatment depends on the type and severity of the problem identified.

Options may include:

prescription glasses;
prism lenses;
Vision Therapy;
strategies to reduce visual strain;
referral for further eye or medical assessment where appropriate.

Following your assessment, we will explain the findings and discuss the most appropriate management options.