Quantifying ageing effect on gaze dynamics

Abstract

In an effort to develop new tools for the classification of neurodegenerative diseases, the effect on the ocular motor system and specifically the visuomotor integration has been a field of interest for more than a decade. Where tracking tasks have shown the potential to quantify fine motor skills of the hand, too little is known about the ocular motor behavior during tracking tasks to make it clinically applicable. This paper therefore studies the gaze of the human eye and will quantify the ageing effect on the gaze dynamics in healthy controls, as neurodegenerative diseases can be age-related.

Experiments were conducted with 40 participants divided in two groups of 20-30 yrs and 55-70 yrs old. The tracking tasks designed involved an eye-only tracking task where a target had to be followed by the eyes alone and an eye-hand tracking task involving the hand to track an element as well. As an addition to the gaze dynamics, the hand dynamics during the eye-hand tracking task has been identified too. Two quasi-random forcing functions of increasing bandwidth (increasing difficulty) were used, making it possible to create models for the gaze dynamics and the hand dynamics. Overall, the gaze performance of the older group was worse than the gaze performance of the younger group, apparent in a lower gain parameter when changing task condition and a higher time constant in the eye-hand tracking condition for older people. The second-order model parameters did not show the expected differences. Additionally, similar yet not significant results were found in the hand dynamics. This research was able to identify an ageing effect in the gaze dynamics and the experiments can therefore be extended to research with patients, using the generated results as normative database.