Visual Dependence and Multisensory Balance Exercise

Older people often find it difficult to maintain balance with their eyes closed, which emphasizes the importance of vision. The greater influence of vision on orientation and balance has been observed by manipulating static and dynamic visual cues-for instance, tilting the frame of reference or moving visual scenes. Older people-particularly those prone to falls-have been reported to make significantly greater errors in subjective visual verticality and exhibit greater sway and continued center of gravity oscillation during and following visual disturbances. They also adopted hip strategies to restore balance in response to visual perturbation, indicating that they were unstable in the event of visual disturbance. These results indicate that older people may have higher levels of visual dependence than younger adults.

The underlying mechanism of visual dependence remains unclear. Visual dependence is considered a form of sensory reweighting deficit. In a situation of sensory conflict, the central nervous system must first recognize the discrepancy and reduce the weighting (suppress) of the inaccurate input while increasing the weighting of the input from the sensory systems that are deemed to provide more reliable information. This complex process of sensory organization is termed multiple-sensory reweighting and is vital in maintaining balance and orientation in a continuously changing and complex environment.

Studies have suggested that visual dependence could benefit from promoting desensitization and increased visual motion tolerance through visual adaptation and habituation exercises in vestibular rehabilitation. This may be because the majority of visually dependent adults have the comorbid symptom of visual vertigo. However, according to the National Audit Survey in the United States, one-third of patients with vestibular disorders and visual dependence lack signs and symptoms of dizziness or vertigo. Recent evidence has demonstrated that healthy older adults with greater levels of visual dependence did not have dizziness; therefore, it is unclear whether visual adaptation exercises can effectively reduce the degree of visual dependence in such people. However, visual dependence can be considered as a sensory reweighting deficit; therefore, multisensory balance training with manipulation of the visual, vestibular, and proprioceptive inputs could be an alternative for decreasing visual dependence through improving the integration and reweighting of sensory systems. In fact, multiple studies have documented that multisensory balance training improves mobility and balance in older adults with instability or a history of falls; however, few have investigated its effectiveness on visual dependence and in healthy elderly people. Therefore, the aim of the study was to investigate the effectiveness of multisensory balance training on the levels of visual dependence and sensory organization capacity in older adults.

Inclusion criteria

• 1) age more than 60 years
• 2) able to walk continuously for 10 meters independently without aid
• 3) normal cognitive function with a Mini-Mental State Examination score more than 24
• 4) able to follow oral commands.

Exclusion criteria

• any medical condition or recent injury that could affect the assessment of balance.