Contribution of Ambient Lighting and Optical Blur on Balance During Sit-to-Stand Movements

Abstract

Purpose : The sit-to-stand (STS) movement is a fundamental, transitional movement that is an essential prerequisite to walking and is important for independent living. The task requires accurate balance to maintain stability and prevent falls, and can occur under low luminance conditions, such as getting out of bed at night. This study investigated the impact of ambient lighting and simulated vision impairment (optical blur) on balance control during STS movements.

Methods : Balance was measured during STS movements in 24 young adults (M= 23.6 ± 4.4 yrs) with no visual, physical, or vestibular impairments. The STS movements were performed under three lighting conditions (photopic, mid-mesopic and low-mesopic) and two vision conditions (best-corrected and with +1.50DS blur). An electronic force plate (HURLabs) recorded centre of pressure trace length (CoP-TL) across three phases of the STS movement: a 2-second dynamic phase while rising from a seated position, followed by two consecutive quiet standing phases (both 10-seconds). All conditions were performed in random order, with somatosensory system input disrupted using a foam surface.

Results : As expected, there was a significant effect of phase on postural stability during the STS movement (p<0.001), with greater stability (lower CoP-TL values) shown across the consecutive phases (all differences p<0.001). Importantly, postural stability was significantly decreased under both mesopic lighting conditions compared to photopic (p<0.001), and this effect was consistent across the three phases of the STS movement. However, there were no differences in stability between the two mesopic conditions (p=0.22). The effect of vision condition on balance tended towards significance (p=0.051), with a trend for greater instability with optical blur compared to best-corrected, across all STS phases.

Conclusions : This research provides valuable insight into visual input for balance control, and highlights the importance of appropriate lighting and optical correction on balance, particularly during critical functional movements such as STS. Future work will explore these effects in older adults with vision impairment, and assist in developing strategies that enable safer mobility and reduce falls risk.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Postural stability during the sit-to-stand phases under the three light conditions and two vision conditions.