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BACKGROUND: Visual sampling (VS) is an active and dynamic process which is driven by task-orientated behavioural and cognitive activity. An integral component of VS is the ability to redirect the eyes to stimuli relevant to the task being undertaken. Measurement of eye movements during real-world activities has become increasingly popular and devices capable of tracking eye movements during such activity have recently been developed. However, to date the reliability of these devices has not been measured. AIM: To evaluate the retest reliability of a Dikablis mobile eye tracker to measure saccadic activity in healthy older adults whilst sitting, standing and walking.METHODS: A Dikablis (Erogneers, GmbH) mobile head-mounted eye tracker (sampling at 50Hz) was used to measure saccadic activity in 20 older adult subjects (≥50 years old) who were assessed on two occasions a week apart. Participants had normal or corrected to normal (via contact lenses or glasses) vision. Subjects were required to make guided eye movements between two visual targets at predetermined horizontal and vertical distances (i.e. 5°, 10° and 15°) in time to an auditory cue (a 60bpm metronome). This was performed while seated with restricted head movement, standing and while walking on a treadmill at 80% of comfortable gait speed. Data were analysed using custom MatLab (Mathworks, Natick, MA) software. Saccades were classified using specific characteristics such as velocity, acceleration, amplitude and duration. Data were inspected using Bland & Altman plots for this preliminary analysis on five subjects.RESULTS: Saccadic accuracy was variable between sessions (range 0.3°-3.7°). Between-session saccadic accuracy was also variable depending on the task e.g. for walking compared to sitting and standing, and standing compared to sitting. Vertical saccades were less accurate than horizontal, particularly at 15°. Increased variability was observed in the vertical direction during all tasks. Overall saccadic accuracy was within ~4°, with limits of agreement ~5°.CONCLUSIONS: The Dikablis mobile eye-tracker is capable of measuring saccades in older adults with 5° error. Eye-tracker reliability may be influenced by a number of factors including error derived from calibration quality, eye vs. field camera positioning, head unit movement and the ability to track the pupil through glasses or contact lenses. Further work on a larger sample is underway and will provide more definitive results.
Author(s): Rochester L; Lord S; Galna B; Alcock L; Stuart S
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: 2nd World Congress of the International Society of Posture and Gait Research (ISPGR)
Year of Conference: 2014
Publisher: International Society for Posture & Gait Research