Usability of Three-dimensional Augmented Visual Cues Delivered by Smart Glasses on (Freezing of) Gait in Parkinson’s Disease

Abstract

External cueing is a potentially effective strategy to reduce freezing of gait (FOG) in persons with Parkinson’s disease (PD). Case reports suggest that three-dimensional (3D) cues might be more effective in reducing FOG than two-dimensional cues. We investigate the usability of 3D augmented reality visual cues delivered by smart glasses in comparison to conventional 3D transverse bars on the floor and auditory cueing via a metronome in reducing FOG and improving gait parameters. In laboratory experiments, 25 persons with PD and FOG performed walking tasks while wearing custom-made smart glasses under five conditions, at the end-of-dose. For two conditions, augmented visual cues (bars/staircase) were displayed via the smart glasses. The control conditions involved conventional 3D transverse bars on the floor, auditory cueing via a metronome, and no cueing. The number of FOG episodes and percentage of time spent on FOG were rated from video recordings. The stride length and its variability, cycle time and its variability, cadence, and speed were calculated from motion data collected with a motion capture suit equipped with 17 inertial measurement units. A total of 300 FOG episodes occurred in 19 out of 25 participants. There were no statistically significant differences in number of FOG episodes and percentage of time spent on FOG across the five conditions. The conventional bars increased stride length, cycle time, and stride length variability, while decreasing cadence and speed. No effects for the other conditions were found. Participants preferred the metronome most, and the augmented staircase least. They suggested to improve the comfort, esthetics, usability, field of view, and stability of the smart glasses on the head and to reduce their weight and size. In their current form, augmented visual cues delivered by smart glasses are not beneficial for persons with PD and FOG. This could be attributable to distraction, blockage of visual feedback, insufficient familiarization with the smart glasses, or display of the visual cues in the central rather than peripheral visual field. Future smart glasses are required to be more lightweight, comfortable, and user friendly to avoid distraction and blockage of sensory feedback, thus increasing usability.

The Beneficial Effects of Conventional Visual Cues Are Retained When Augmented Reality Glasses Are Worn

“…Surprisingly, conventional cues, i.e., real transverse bars on the floor and the beat of a metronome, neither afforded beneficial effects while people wore the AR glasses [4,5]. One possible explanation is that the rather bulky AR glasses (that were worn throughout the experiment) in effect caused a "dual task" effect and hence inadvertently diverted the participants' attention away from the walking task [4]. Dual tasks are known to deteriorate FOG in PD patients [6][7][8][9][10].…”

“…External cues, such as transverse bars on the floor or the beat of a metronome, can alleviate freezing of gait (FOG) in people with Parkinson's disease (PD) [1][2][3]. We previously investigated the effects of augmented reality (AR) visual cues on FOG and hypokinetic gait in people with PD but found no improvements [4,5]. Surprisingly, conventional cues, i.e., real transverse bars on the floor and the beat of a metronome, neither afforded beneficial effects while people wore the AR glasses [4,5].…”

“…We previously investigated the effects of augmented reality (AR) visual cues on FOG and hypokinetic gait in people with PD but found no improvements [4,5]. Surprisingly, conventional cues, i.e., real transverse bars on the floor and the beat of a metronome, neither afforded beneficial effects while people wore the AR glasses [4,5]. One possible explanation is that the rather bulky AR glasses (that were worn throughout the experiment) in effect caused a "dual task" effect and hence inadvertently diverted the participants' attention away from the walking task [4].…”

The Effects of Augmented Reality Visual Cues on Turning in Place in Parkinson's Disease Patients With Freezing of Gait

“…Exclusion criteria were significant cognitive impairment [mini-mental state examination score (MMSE) <24 or frontal assessment battery (FAB) score <13], comorbidity causing severe gait impairments, severe bilateral visual or auditory impairments precluding the participant from using the cues, and an inability to perform a 180 • turn unaided. The following questionnaires were taken prior to testing: New Freezing of Gait Questionnaire (NFOG-Q) (23), the MDS-UPDRS part III (24), MMSE (25), and FAB (30). All participants provided written informed consent prior to their inclusion in the study.…”

Sensory Electrical Stimulation Cueing May Reduce Freezing of Gait Episodes in Parkinson’s Disease

“…Various rhythm frequencies for “fixed” rhythmic cueing have been previously evaluated. These range from frequencies (i) equal to the person's typical step rate [13, 16], (ii) set to 10–20% below the person's typical step rate [8, 17, 18], (iii) set to 10–20% above the person's typical step rate [16, 19–21], or (iv) set to a perceived comfortable value [22]. Although the optimal frequency is unclear, it has been suggested that “fixed” rhythmic sensory stimuli help the PwP to synchronize stepping, thus helping them to regulate their gait rhythm.…”