Testing of visual dependency on body sway and its application to balance rehabilitation

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We examined 15 patients with visual vertigo syndrome (VVS). VVS was diagnosed as having dizziness or imbalance triggered by the specific visual environments. There were 9 men and 6 women and their mean age was 43 years, range 25 to 69. The visual environments consisted of looking at TV or computer display (5 patients), driving car in the tunnel (4 patients), walking in supermarkets (4 patients) and walking through a crowd (2 patients). These findings indicate that the specific visual environments containing optical flow induced dizziness in VVS patients. Therefore, it is suggested that visual dependency on body sway is increased in VVS patients. We then developed a new device to produce optical flow stimulation to evaluate visual dependency on body sway. The ratio between sway path with eyes closed and eyes open is called the, Romberg ratio, which showed static visual dependency on, body sway. The Romberg ratio was increased in both healthy volunteers and VVS patients. On the other hand, the ratio between sway path with and without optical flow stimulation showed dynamic visual dependency on body sway. The ratio was markedly increased in some VVS patients, but not in other VVS patients and healthy volunteers. These findings suggested that the increased dynamic visual dependency on body sway is an important mechanism of the development of VVS