Friday, April 18, 2014

Strabismus and body balance - vision therapy and the eye-brain connection

Strabismus and body balance - the eye brain connection, cerebellum dysfunctions may contribute to strabismus, esotropia and exotropia.  Vision therapy may help rehabilitate the malfunction.
An important new study appeared in the journal Vision Research. It confirms the approach that we take to strabismus (eye turns, cross eyes) treatment in our Vancouver eye clinic, where we employ non-invasive optometric vision therapy. Vision therapy is based on the concept of neuroplacitity - the ability of the brain to reorganize itself though a program of rehabilitative therapy and fix problems that arise from the failure of the brain and eyes to communicate properly. One such problem is strabismus, a condition where the eye turns in or out (called esotropia or exotropia). These eye turns are usually not caused by problems with the muscle itself. The problem is in the eye-brain connection that controls eye movement. The new study confirms this approach to treating strabismus.

This study investigated how the information from eye-muscles muscles affects postural stability in adults with binocular vision disorders and demonstrated that those with binocular vision disorders showed significantly worse balance control than those without binocular vision disorder, even when they were only using only one eye. The study showed that inaccurate signals related to the eye muscles impact body balance and that this effect can last into adulthood even where subjects had surgery as children to make the eyes appear straight. The second part of their study shows that specific therapeutic tasks can allow patients with strabismus to develop better body balance.

The study adds to the growing body of research that suggests that strabismus is a whole-body problem that results in impairments, adaptations and compensations on many levels throughout the body, which often last into adulthood.  The researchers suggest that a dysfunction in a part of the brain called the cerebellum may contribute to strabismus. The cerebellum plays an important role in eye movement coordination and alignment. Recent studies have shown that the cerebellum is also involved in cognitive functions including attention. Based on this, the researchers thought that the attentional effort required for the mental task in their study resulted in activation of the cerebellum which decreased inhibition from the strabismic eye, which in turn lead to greater postural control.

Here is a passage form a commentary by Dr. Leonard J Press OD, FAAO, FCOVD and Dr. Joseph D Napolitano MD on why this research is so exiting:

Why is this research exciting? It counteracts the notion that strabismus is an isolated eye muscle problem that has little bearing other than cosmesis. The appearance of the eyes is only one feature of strabismus, better appreciated as a difficulty in multimodal coordination. This presents new opportunities to conceive of the synergy between extra-ocular muscle (EOM) surgery and optometric vision therapy, somewhat analogous to the synergy between orthopedic surgery and physical therapy.
When conceived in this fashion, the cognitive and attentional resources employed in optometric vision therapy help the brain to coordinate both eyes through activities mediated through the cerebellum. Even when [eye muscle] surgery or optometric vision therapy do not achieve bi-foveal alignment or random dot stereopsis, very meaningful gains can be realized in improved head to toe motor control.
The role of vision therapy features prominently in this study.  Here is what the authors say:
These findings emphasize the role of the eye-muscle signals in postural control and suggest that suitable vision therapy can be the appropriate way to improve body balance/motor functions in people with binocular vision disorders.


Vision Research
Impaired Body Balance Control in Adults With StrabismusVision Res 2014 May 01;98(-)35-45, A Przekoracka-Krawczyk, P Nawrot, M CzaiƄska, KP Michalak

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