Abstract
Subjects with low vision often use a cane when standing and walking autonomously in everyday life. One aim of this study was to assess differences in the body stabilizing effect produced by the contact of the cane with the ground or by the fingertip touch of a firm surface. Another aim was to estimate the promptness of balance stabilization (or destabilization) on adding (or withdrawing) the haptic input from cane or fingertip. Twelve blind subjects and two subjects with severe visual impairment participated in two experimental protocols while maintaining the tandem Romberg posture on a force platform. In one protocol, subjects lowered the cane to a second platform on the ground and lifted it in sequence at their own pace. In the other protocol, they touched an instrumented pad with the index finger and withdrew the finger from the pad in sequence. In both protocols, subjects were asked to exert a force not granting mechanical stabilization. Under steady-state condition, the finger touch or the contact of the cane with the ground significantly reduced (to ∼78% and ∼86%, respectively) the amplitude of medio-lateral oscillation of the centre of foot pressure (CoP). Oscillation then increased when haptic information was removed. The delay to the change in body oscillation after the haptic shift was longer for addition than withdrawal of the haptic information (∼1.4 s and ∼0.7 s, respectively; p < 0.001), but was not different between the two haptic conditions (finger and cane). Similar stabilizing effects of input from cane on the ground and from fingertip touch, and similar latencies to integrate haptic cue from both sources, suggest that the process of integration of the input for balance control is initiated by the haptic stimulus at the interface cane-hand. Use of a tool is as helpful as the fingertip input, and does not produce different stabilization. Further, the latencies to haptic cue integration (from fingertip or cane) are similar to those previously found in a group of sighted subjects, suggesting that integration delays for automatic balance stabilization are not modified by visual impairment. Haptic input from a tool is easily exploited by the neural circuits subserving automatic balance stabilization in blind people, and its use should be enforced by sensory-enhancing devices and appropriate training.
Highlights
Subjects with visual impairment often use a cane to move autonomously in everyday life (Jeka, 1997)
Pioneering studies by Holden et al (1994), Jeka and Lackner (1994), and Jeka et al (1996) in sighted subjects showed that the simple contact by a finger with a solid frame is as effective as the sight of the surrounding environment in reducing postural sway when compared to no contact, eyes closed condition
The post hoc test showed that the oscillations were always larger under NT than T condition (p < 0.001, d > 0.6 for all four comparisons), and were slightly smaller in the M-L direction when holding the cane without touching the ground than during the finger no-touch condition (p < 0.001, d = 1.1)
Summary
Subjects with visual impairment often use a cane to move autonomously in everyday life (Jeka, 1997). Pioneering studies by Holden et al (1994), Jeka and Lackner (1994), and Jeka et al (1996) in sighted subjects showed that the simple contact by a finger with a solid frame is as effective as the sight of the surrounding environment in reducing postural sway when compared to no contact, eyes closed condition. The force levels exerted by the finger or by the cane were below those necessary to provide significant mechanical stabilization. Contact of a cane with the ground has been shown to be effective in reducing postural sway in both sighted subjects and in small cohorts of non-sighted subjects as well (Jeka et al, 1996; Albertsen et al, 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
