Effective orientation and balance are based on the integration of visual, vestibular, and proprioceptive sensory inputs. Vision plays a significant role in spatial orientation and posture maintenance; however, a static tilted frame or dynamic rotating visual disturbance can affect orientation and balance. Visual dependence (VD) is a term used to describe people who overly rely on visual information. Individuals with VD have difficulty in resolving situations wherein visual information is complex or inaccurate. They show greater postural instability and complain of incidences of dizziness and vertigo in sensory conflicting conditions, such as walking along the pavement or the aisle of a supermarket. The Romberg test and the Sensory Organization Test are commonly used to assess the influence of vision on postural control, whereas the Rod and Frame Test and Rod and Disc Test are used to evaluate VD levels at the perceptual level. However, VD mechanisms are still unclear. VD may be associated with vestibular or proprioceptive impairments. Recent studies have reported that VD is more likely to be affected by vestibular rather than proprioceptive inputs. VD is also considered to be a kind of sensory reweighting deficit. People with VD are unable to flexibly reduce the weighting of inaccurate input (vision) while increasing the weighting of input from the sensory systems (proprioceptive or vestibular systems) to provide more reliable information. VD is often reported in older adults; however, it may be due to the age-related decline of peripheral sensory systems and not due to aging as such. An impaired egocentric reference frame could be another contributing factor because the visual reference frame might compensate to become dominant in determining the orientation. VD needs more attentional demands that may share cognitive loads with the maintenance of balance; thus, it may increase postural instability and the risk of falls. Visual habituation exercise, such as optokinetic stimulation training, could increase tolerance in response to visual motion and decrease VD levels by using repeated presentation of the same visual stimuli. However, the type, intensity, frequency, and duration of treatment for VD are not conclusive; therefore, further investigation regarding rehabilitation exercises for VD is needed.
- visual dependence
- visual habituation exercise