Evaluating eye-body coordination during unrestrained functional activity in older persons.

BACKGROUND Traditional paradigms for the study of ocular-motor control restrain subject motion and have not adequately quantified the sensorimotor strategies used by older persons to control gaze while performing activities of daily living. The purpose of our study was to describe eye-head-trunk coordination during a functional activity in freely moving community-dwelling older persons. METHODS Thirty-five community-dwelling older persons (age range 71-92 years) participated in this study. Surface electro-oculography was used with an electromagnetic tracking device to measure vertical eye movement and linear and angular head position while each subject performed a stand-from-chair task. RESULTS Standing from a chair involved low-frequency head motion (median z = 0.25 Hz; median pitch = 0.32 Hz). The distribution of phase for eyes versus vertical body motion were skewed toward head-trunk leading, suggesting that eye motion follows vertical body motion. Vertical gaze, however, was in phase with and moved in the same direction as head pitch. CONCLUSIONS Gaze (eye position in space) was an active, integrated component of the standing motion. The results imply that both the oculomotor system and the head motor system in older persons are coordinated to direct gaze and, when necessary, work to suppress the vestibuloocular reflex. The interaction of eye-head-trunk motion provides a basis for understanding how a breakdown in the gaze control mechanisms in older persons might contribute to the risk of falling and fall-related injuries.