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Vision therapy for binocular vision dysfunction

• Convergence
• Accomodation
• Impact on academics
• Prevalence of binocular dysfunctions in students

Binocular vision dysfunction

General binocular dysfunction is the inability to move your eyes together in an effective manner.  Each eye has six extraocular muscles that move the eyes in a coordinated manner.  this movement is controlled by the brain.  In a pediatric population, the prevalence of binocular disorders have been found to be 9.7 times greater than the prevalence of any other ocular disease.  Subcategories of binocular dysfunction include:

• Accomodatedive 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 commoon 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 followup studies.

Convergence

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 of the RCT provides a short summary of the study.

There have also been follow-up studies by Scheiman et al. showing that the results obtained from vision therapy are were long-lasting and that the treatment kinetics are favorable  – meaning that that rate at which patients get better with vision therapy makes office-based vision therapy an effective and practical treatment .

In 2005 Scheiman et al. published a clinical trial in Optometry and Vision Science on the vision therapy treatment of convergence insufficiency in young adults ages 19-30. Once again, the results proved the efficacy of vision therapy treatment over other modalities that were in use at the time. The study authors concluded:

"This first multicenter, randomized clinical trial of the treatment of symptomatic CI in young adults demonstrated that of the three treatment modalities, only vision therapy/orthoptics was effective
in achieving normal clinical values for both the near point of convergence and positive fusional vergence. Patients in the pencil pushups group achieved normal values only for positive fusional
vergence at near and patients in the placebo vision therapy/orthoptics group did not achieve normal findings for either the near point of convergence or positive fusional vergence at near. Therefore, the effectiveness of vision therapy/orthoptics in improving the near point of convergence and positive fusional convergence values at near in adults cannot be explained on the basis of a placebo effect. Based on the results of this preliminary study, it would appear that
pencil pushups, the most popular treatment for CI, is not effective for achieving clinically significant improvements in symptoms or signs associated with CI in young adults." [emphasis added]

A study published in 2010 by Alvarez et al. in Optometry and Vision Science adds to the depth of the scientific evidence by showing that vision therapy produced demonstrated changes in eye movements together with significantly increased functional activity within the frontal areas of the brain, the cerebellum, and brain stem. These regions of the brain are likely to ―participate in a collicular-cortical dorsal visual networks and may reflect increased processing of visual material specific to near space.‖ This study demonstrates the motor and neurological mechanism by which vision therapy operates. The brainscan images published in the Alvarez study are worthy of review.

Accomodation

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/orthoptics is effective in improving accommodative amplitude and accommodative facility in school-aged children with symptomatic CI 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).

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 despite the presence of a documented brain injury. In a 2008 study by Ciuffredaet al. published in the journal Optometry, 90% of patients with mild traumatic brain injury had significant improvement in their 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.

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 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).

How prevalent is binocular dysfunction among students?

A 1997 study by Porcar and Martinez-Polomero published in the journal Optometry and Vision Science concluded that acommodative and nonstrabismic 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.

These are MRI images of the brain before and after vision therapy as well as images taken at a later followup visit published as part of a study by Alvarez et al. who discuss the images as follows: "Images on the left column are the average of the before vision therapy data set, the middle column are after vision therapy, and the right column are from a follow-up scan. On average, increases in spatial extent (amount of significant activation) and/or intensity are observed when comparing the before and after scans." Source: Alvarez et al.Vision therapy in adults with convergence insufficiency: clinical and functional magnetic resonance imaging measures. Optom Vis Sci. 2010 Dec;87(12):E985-1002.

Optometrist, Dr. Elise Brisco on "The Doctors" talking about binocular vision disorders (especially double vision) and - near the end of the video - vision therapy.

http://www.thedoctorstv.com/videolib/init/3086