Influence of the Visual Environment on the Postural Stability in Healthy Older Women

Abstract

Background: A poor postural stability in older people is associated with an increased risk of falling. It is recognized that visual environment factors (such as poor lighting and repeating patterns on escalators) may contribute to falls, but little is known about the effects of the visual environment on postural stability in the elderly. Objective: To determine whether the postural stability of older women (using body sway as a measure) differed under five different visual environment conditions. Methods: Subjects were 33 healthy women aged 65–76 years. Body sway was measured using an electronic force platform which identified the location of their centre of gravity every 0.05 s. Maximal lateral sway and anteroposterior sway were determined and the sway velocity calculated over 1-min trial periods. Body sway was measured under each of the following conditions: (1) normal laboratory lighting (186 lx); (2) moderate lighting (10 lx); (3) dim lighting (1 lx); (4) eyes closed, and (5) repeating pattern projected onto a wall. Results: Each measure of the postural stability was significantly poorer in condition 4 (eyes closed) than in all other conditions. Anteroposterior sway was greater in condition 3 than in conditions 1 and 2, whilst the sway velocity was greater in condition 3 than in condition 2. Lateral sway did not differ significantly between different lighting levels (conditions 1–3). A projected repeating pattern (condition 5) did not significantly influence the postural stability relative to condition 1. Conclusions: The substantially greater body sway with eyes closed than with eyes open confirms the importance of vision in maintaining the postural stability. At the lowest light level, the body sway was significantly increased as compared with the other light levels, but was still substantially smaller than on closing the eyes. A projected repeating pattern did not influence the postural stability. Dim lighting levels and removing visual input appear to be associated with a poorer postural stability in older people and hence might be associated with an increased risk of falls.

The Influence of Very Low Illumination on the Postural Sway of Young and Elderly Adults

“…Therefore, we conclude that very low level of ambient illumination altered postural steadiness but significantly less so than did both of the no vision conditions. These results agree with those of Simoneau et al [20] who reported a minimal effect of dim light on postural sway (from 2.6 to 11 per cent for different time domain variables) and the results of Brooke-Wavel et al [6] who reported increased sway in dim light. The visual referencing differed between our study and that of Brooke-Wavel et al [6] in terms of the spatial referencing markers; in our study, a single reference point was placed in front of the participants, while Brooke-Wavel et al [6] used vertical lines to structure the environment.…”

“…The illuminance in the dark room at the gaze fixation point was estimated to be 0.25 lx. This is the lowest level of illumination that has been reported (3 lx: [3], [13] and [20], 1 lx: [6]). It seems that the amount of light provided in this condition was not sufficient for accurate visual referencing and resulted in increases in postural sway.…”

“…However, for elderly populations, the reported results regarding the influence of very low ambient illumination are conflicting. Some authors have reported increases in postural sway in environments with very low illumination compared to those with normal illumination [3], [6], [13], while others were unable to find any significant increase in postural sway [20].…”

“…The effect of the absence of visual information on balance can be assessed by the time for which a person is able to stand with their eyes closed [2] and can be measured as changes in postural steadiness via stabilometry [3], [4]. It has often been reported that, without visual information, postural steadiness significantly decreases [3], [4], [5], [6], [7]. This phenomenon has been documented in both young and older persons [7], [8], and postural sway is typically larger in elderly persons than in middle-aged and young persons [9], [10], [11], [8].…”

“…It has been shown that the postural response of the elderly to low illumination can increase the risk for instability and falls [16]. Low levels of illumination and the optical patterns associated with specific surface layouts (e.g., escalators) have been identified as environmental factors that have detrimental effects on older people’s postural controls [6]. The rate of falls in elderly adults with poor vision is markedly higher than that among the elderly with normal vision [17].…”