Binocular vision dysfunction


>Signs and symptoms

>Convergence insufficiency

>Accomodative dysfunction

>Examples of vision therapy treatment

>Impact on school and academic performance

General binocular dysfunction is the inability to move your eyes together in an effective manner. Each eye has six eye muscles that move the eyes in a coordinated manner. This movement is controlled by the brain. In a paediatric population, the prevalence of binocular disorders have been found to be 9.7 times greater than the prevalence of any other ocular disease.  Vision therapy has proven to be a safe and effective treatment for binocular vision dysfunctions, even when they are caused by a traumatic brain injury.


For example, a recent study in the October 2013 issue of the journal Binocular Vision & Strabismus Quarterly, entitled, "Evaluation of Binocular Vision Therapy Efficacy by 3D Video-Oculography Measurement of Binocular Alignment and Motility" demonstrated that binocular vision therapy was effective when applied to two patients with divergence excess.  The therapy procedures conducted come from classical optometric vision therapy, including included Hart Charts, Brock String, consciousness of physiological diplopia, accommodative facility with lens flippers, Aperture Rule, vectograms, and vergence facility.  


Subcategories of binocular dysfunction include: 

Accommodative disorders


The inability of the eyes to focus. The eyes must be able to sustain focus for long periods of time when doing near work. Also, the eyes must be able to quickly and accurately change focus from distant to near objects.


Convergence disorders


The inability to use both eyes as a team when looking at something up close. When looking at near objects, both eyes should turn inwards and maintain single vision.

Divergence disorders


The inability to use both eyes as a team when looking at something in the distance. When looking at far away objects, both eyes should turn outwards and maintain single vision.

Oculomotor disorders


The inability to quickly and accurately move our eyes. These are sensory motor skills that allow us to move our eyes so that we can fixate on objects (fixation), move our eyes smoothly from point to point as in reading (saccades) and to track a moving object (pursuits).


The most common binocular vision problems are dysfunctions of convergence and accommodation. The vision therapy treatment of both convergence and accommodation problems has been recently proven in randomized clinical trials and related follow-up studies.


Signs and symptoms of general binocular vision dysfunction


The following are oculomotor and visual symptoms of binocular vision dysfunction.


  • Avoidance of near tasks
  • Oculomotor-based reading difficulties
  • Eye tracking problems
  • Eye focusing problems
  • Eyestrain
  • Diplopia
  • Dizziness
  • Vertigo
  • Vision-derived nausea
  • Increased sensitivity to visual motion
  • Visual inattention and distractibility
  • Short-term visual memory loss
  • Difficulty judging distances (relative and absolute)
  • Difficulty with global scanning
  • Difficulty with personal grooming, especially involving 
    the face
  • Inability to interact/cope visually in a complex social 
    situation (e.g., minimal eye contact)
  • Inability to tolerate complex visual environments (e.g. grocery store aisles and highly-patterned floors)



The following are clinical signs of binocular dysfunction that eye doctors can measure in the examination room:


  • Reduced amplitude of accommodation
  • Increased lag of accommodation
  • Reduced relative accommodation
  • Slowed accommodative facility
  • Uncorrected hyperopia/ astigmatism (due to inability to 
    compensate accommodatively)
  • Receded near point of convergence
  • Restricted relative convergence (BO) at far and near
  • Restricted overall fusional vergence ranges at far and near
  • Abnormal Developmental Eye Movement test (DEM) results
  • Low grade-level equivalent performance on the Visagraph II
  • Impaired versional ocular motility


Convergence insufficiency


A number of research studies have proven the effectiveness of the vision therapy treatment of convergence insufficiency. Scheiman et al. completed a randomized controlled trial funded by the National Eye Institute to assess the efficacy of vision therapy in treating convergence insufficiency, which is the most common binocular vision problem, in 9-17 year-olds. The results were published in 2008 in the journal Archives of Ophthalmology and demonstrate conclusively that office-based vision therapy was the most effective treatment for convergence insufficiency, with 75% of patients achieving normalization of or improvement in symptoms and signs within 12 weeks. As the authors note, the vision therapy procedures employed may have to be appropriately modified for older individuals.

Notably, it was also found that the most popular treatment typically offered by ophthalmologists, pencil push-ups, was not effective. The press release issued by the National Eye Institute to announce the findings  provides a short summary of the study.


To learn more about convergence insufficiency, click here.

Accommodive dysfunction

In August, 2011 the Scheiman et al. study group published new clinical trial on the efficacy of vision therapy in treating individuals 9-17 years old who suffer from another binocular vision problem: accommodative dysfunction.  The study concluded that vision therapy is effective in improving accommodative amplitude and accommodative facility in school-aged children with symptomatic convergence insufficiency and accommodative dysfunction. This is an expected result, as all binocular dysfunctions are closely related and so are expected to respond equally well to similar treatment.  


Further, while the recent clinical trials improve the literature on vision therapy, they merely confirm what clinicians already know from decades of treating patients and seeing the results as well as from the numerous case reports, case series, cohort studies and early controlled studies already published.

The clinical trials discussed above are significant in that convergence and accommodation are the two components of binocular vision and the vision therapy treatment of deficits in both has now been proven effective in randomized controlled trials.


Examples of the vision therapy treatment of binocular vision problems


In addition to the clinical trials discussed above, the literature is filled with reports and case series of vision therapy treatment for binocular problems. 


A number of cases involving healthy brain patients are reviewed in a study by Ciuffreda (2002). In addition to the latter, older but widely cited literature reviews showing the efficacy of vision therapy in treating the various forms of binocular dysfunction were published in 1987 in the American Journal of Optometric and Physiological Optics as part of a vision therapy symposium. These studies by Rouse (on accommodative deficiencies), Duckman (on exotropia), and Griffin (on vergence) demonstrate the long-stating and effective use of vision therapy to treat binocular vision problems.

However, perhaps the best illustration of the efficacy of vision therapy comes from studies that investigated vision therapy in patients whose binocular problems did not originate organically but rather were the result of mild traumatic brain injuries (mTBI).

In mTBI cases, which are much more challenging than patients with healthy brains, vision therapy was an effective treatment for binocular vision problems even with the challenging presence of a documented brain injury. In a 2008 study by Ciuffreda et al. published in the journal Optometry, 90% of patients had significant improvement in their binocular dysfunction symptoms.

Optometric researchers have also published studies in the neurological literature such as a 2002 study by Kapoor and Ciuffreda in the journal Current Treatment Options in Neurology, where the authors stated that binocular vision problems such as problems of accommodation, vergence, version and other are amenable to optometric vision therapy:


Anomalies of accommodation, vergence, version, photosensitivity, and field of vision are amenable to noninvasive, rehabilitative interventions, such as vision therapy, which is rendered by optometrists and is described in this article. Further, vision therapy may be performed in isolation or in conjunction with the application of the following:


  • Fusional prism spectacles (for diplopia)
  • Tinted spectacles (for photosensitivity)
  • Yoked prism spectacles (for visual-spatial hemispheric inattention, 
    with or without a manifest visual field defect), as appropriate

Do binocular vision problems affect academic performance?


Several studies suggest that the answer is, "yes".

A 2010 study published in the journal BMC Ophthalmology by Dusek at al. investigated the visual functioning of two groups of school-aged children in Austria - one group that was diagnosed with reading and writing difficulties and the other which was a clinical age-matched control group. 


The study found that the group of children with reading difficulties was statistically more likely to have visual problems such as poorer distance visual acuity, an binocular problems such as exophoric deviation at near, a lower amplitude of accommodation, reduced accommodative facility, reduced vergence facility, a reduced near point of convergence, a lower AC/A ratio and a slower reading speed. 

The study confirmed the importance of a full assessment of binocular visual status in order to detect and remedy these deficits in order to prevent the visual problems continuing to impact upon educational development.

Similar results come from a 2007 American study by Grisham et al. published in the Journal Optometry, entitled "Visual skills of poor readers in high school"  that measured visual skills and visual acuity in 461 students with an average age of 15.4 years in four California high schools within the same school district. Participating students had been identified by their schools as poor readers.

In the studied sample, 80% of the students were found to be inadequate or weak in one or more of the following binocular visual skills: binocular fusion ranges at near, accommodative facility, and convergence near point. In contrast, only 17% had deficient visual acuity—20/40 or worse in one eye— which is the standard model of deficiency for school vision screenings. This demonstrates not only the inadequacy of school vision screenings but also that academic deficits are correlated much more strongly with binocular vision problems (which can’t be fixed with corrective lenses) rather than with acuity (which can be fixed with corrective lenses).


A new study reached similar results. The study, entitled Association between reading speed, cycloplegic refractive error, and oculomotor function in reading disabled children versus controls was published in the May 2012 issue of the journal Graefes Archives of Clinical Experimental Ophthalmology. The study was prompted by the fact that one in ten students aged 6 to 16 in Ontario have an individual education plan (IEP) in place because of various learning disabilities. May of those learning problems were specific to reading. They wanted to investigate the relationship between reading vision problems and binocular vision problems. Here is the study's conclusion:

This research indicates there are significant associations between reading speed, refractive error, and in particular vergence facility. It appears sensible that students being considered for reading specific IEP status should have a full eye examination (including cycloplegia), in addition to a comprehensive binocular vision evaluation.

How prevalent is binocular dysfunction among students?


The research indicates that binocular vision dysfunction is a  big problem among students. A 1997 study by Porcar and Martinez-Polomero published in the journal Optometry and Vision Science, entitled "Prevalence of General Binocular Dysfunctions in a Population of University Students", concluded that accommodative and non-strabismic binocular vision problems are prevalent in the university population. accommodative excess is the most common condition. Because these dysfunctions have a negative effect on performance, appropriate vision evaluation for this population is important. The researchers concluded that among university students, 32.3% showed general binocular dysfunctions. In 10.8% of the cases, accommodative excess was present. 7.7% had convergence insufficiency with accommodative excess. 6.2% showed accommodative insufficiency. 3.1% had basic exophoria.

More recently, a longitudinal study was published by Jorge et al. in 2008 in Optometry and Vision Science the purpose of which was to investigate the changes in accommodation and binocular vision parameters during a 3-year period. The research team found significant changes in near heterophoria, fusional vergences, and positive relative accommodation.

These two studies indicate that binocular dysfunction is not rare in university students and that the demands of university appear to worsen binocular vision over time




.A number of studies have looked at the impact of binocular vision problems on reading and school performance they have found a significant link between. academic and reading problems and treatable binocular vision problems. These studies, some of which are discussed above, demonstrate that children with reading or other academic problems need to be evaluated by a developmental optometrist and treated if a problem is found. Too often, parents waste thousands of dollars on extra tutoring and think that a child is lazy and needs to work harder. The reality often is that the child's visual system is not functioning properly because of a binocular vision problem that can be treated with vision therapy. 


Is your child smart in everything except school?

Convergence insufficiency infographicContent


ADHD and convergence insufficiency research summary


  • Borsting E, Rouse M, Chu R. Measuring ADHD behaviors in children with symptomatic accommodative dysfunction or convergence insufficiency: a preliminary study. Optometry. 2005;76:588–92. [Download]

    The results from this preliminary study suggest that school-aged children with symptomatic accommodative dysfunction or convergence insufficiency (eye movement disorders) have a higher frequency of behaviors related to school performance and attention as measured by the a survey called the Connors Parent Rating Scale–Revised Short Form. The survey uses 27 questions to test a broad range of school-related behaviors in the following categories: oppositional, cognitive problems/inattention, hyperactivity, and ADHD Index. 

  • Granet DB, Gomi CF, Ventura R, Miller-Scholte A. The relationship between convergence insufficiency and ADHD. Strabismus. 2005;13:163–8. [PubMed]. 

    In this study, the researchers found that people diagnosed with ADHD were three times more likely to have convergence insufficiency than the general population. 

  • Gronlund MA, Aring E, Landgren M, Hellstrom A. Visual function and ocular features in children and adolescents with attention deficit hyperactivity disorder, with and without treatment with stimulants. Eye. 2007;21:494–502. [PubMed]. 

    In this study, the researchers found that children diagnosed with ADHD have a higher frequency of eye problems than the general population and that the eye problems did not improve when children were on stimulants, which are the drugs that are commonly prescribed to treat ADHD. 

  • Rause, et al. Academic behaviors in children with and without parent-report of ADHD. Optom Vis Sci. 2009 October; 86(10):1169–1177.[PDF]






Strabismus, 3D & VT

Children's Vision

Convergence Insufficiency

Binocular Vision