Abstract
Purpose:
To measure the visual and somatosensory contribution to postural stability among legally blind participants and normals using the NintendoTM Wii Balance Board (WBB) as a posturography device.
Methods:
Fourteen legally blind participants (age μ = 51, σ = 16; 4 Males) and 21 participants with corrected-to-normal vision (age μ = 26, σ = 8; 5 Males) completed the modified Clinical Test of Sensory Interaction (mCTSIB). Center of Pressure (COP) data was collected during four sensory conditions: double leg standing on a firm surface with eyes open (firm-EO); on a firm surface with eyes closed (firm-EC); on an unstable surface with EO (foam-EO); and on an unstable surface with EC (foam-EC). Subjects performed each condition for 3 successive 30-second trials with a rest period in between. The conditions were randomly ordered. Mean Total Velocity COP (mm/s) was derived from data sent by the 4 force plate sensors in the WBB to a laptop via Bluetooth.
Results:
The Romberg quotient (RQ) was calculated to determine the visual contribution (EC/EO on foam). Higher RQ equals greater visual contribution. An analysis of covariance (adjusting for age), indicated the visual contribution to mean total velocity (mm/s) was smaller for visually impaired (VI) than for normally sighted individuals under conditions where the somatosensory system was disrupted (i.e. upright stance on foam) (VI Mean (SD) RQ = 1.16, Normal Mean (SD) RQ = 1.91; F(1,32)=13.76, p = 0.001) consistent with previous results (Kotecha, 2012). To determine the relative somatosensory contribution to postural stability, the difference between foam and firm conditions was calculated for EO. Adjusting for age, results found significant differences between the VI and normal groups (VI Mean Δ (SD) = 12.61 (6.08), Normal Mean Δ (SD) = 3.74 (1.96); F(1, 32) = 7.75, p = 0.009)).
Conclusions:
These data provide evidence that the WBB is sensitive to sensory inputs in a VI versus normal population. Persons with VI had lower visual contribution to balance and greater instability in somatosensory conditions, thus putting them at greater risk for falls. Using the WBB as a basic posturography device may be clinically useful for measuring postural stability in patients with acquired vision loss and represents a cost-effective and accessible quantitative outcome for future research.