The impact of vertical eye movements on postural control during upright standing in community-dwelling older adults

Abstract

【Purpose】Eye movements affect postural control in the elderly. However, the effects of smooth pursuit eye movements (SPEMs) and vertical eye movements remain unclear. To determine the effects of vertical eye movements on postural control in community-dwelling elderly, postural sway in an upright standing position during saccadic eye movements (SEMs) and SPEMs was examined.

【Materials and Methods】We enrolled 20 elderly (75.6±5.0 years) and 13 young (21.6±0.9 years) adults. Eye and head movements and postural sway were measured during horizontal and vertical SEMs and SPEMs at a 30°visual angle and 0.33 Hz while the subject wore the eye tracker Tobii Pro Glasses 3 and stood on the force platform in an upright stance. The estimated gain during eye movements, the absolute value of the angular speed of head rotation, and the lengths of the trajectories in the mediolateral and anteroposterior directions were used for analysis.

【Results】During vertical eye movements, the trajectory length of the postural sway in the anteroposterior direction increased in the elderly (p = .049 for SEMs, p = .014 for SPEMs), and it increased more during SPEMs than during SEMs (p=.048). In the elderly, the estimated gain during vertical SEMs was smaller compared to the gain during horizontal SPEMs (p = .024) and to the value for the young adults (p = .009). The estimated gain during SEMs was small for both horizontal and vertical movements (p＜.001) and the gain for the vertical movements was even smaller (p = .014), which was different from the results observed in the young adults. No significant differences in the head movements were observed between the elder and young subjects.

【Conclusion】In the elderly, postural sway in the anteroposterior direction increased more with vertical eye movements than with horizontal eye movements; and this was particularly observed during SPEMs. This could be associated with the difference from the young adults' gain during vertical eye movements.