Dynamic stability in low vision and normal subjects during dual-task activity

Visual system has a major role in balance control and provides information about the position of body and head in relation to surrounding objects and in the space. One of the health problems, especially in developing countries, is the high incidence of low vision in different age groups (3.1%). The visual deficit in these patients may affect their balance during daily activities which usually involve concomitant tasks such as walking and speaking. Therefore, the effect of concurrent cognitive activity on the postural control of patients with low vision was investigated. twenty low vision volunteers (age 32±5, weight 71±17 kg, height 167±14 cm) and twenty normal subjects (age 33±4, weight: 72±14 kg, height: 170±9 cm) were recruited in this study. The dynamic stability score was evaluated by Stabilometer (Biodex, England) in three different standing positions (eyes open, eyes closed and eyes open with a cognitive task). Lower stability score represents better stability. The stability score in open eyes condition with or without dual task in normal group was lower than low vision group (P=0.04). However, in closed eyes condition, it was lower in low vision group compared to normal group (P=0.03). Dual task resulted in increase in the stability score in both groups; however, the changes were only significant in low visions (P=0.04). The results represent the higher reliance of normal subjects to visual inputs for balance control. The decreased balance control in low vision groups during dual task suggests the higher usage of their limited central integration capacity in balance control. This may predispose this group of patients to falling accidents during daily activities which may involve several concomitant tasks.