Visual sampling in Parkinson's disease: current methodological issues Stuart S, Alcock L, Galna B, Lord S, and Rochester L Institute for Ageing and Health, Newcastle University http://research.ncl.ac.uk/hmst |
[email protected]
Introduction • Robust measurement of visual sampling (VS) is critical to understanding vision during real-world activities. • Strategies used during VS may be different for people with Parkinson’s disease (PD) compared to older adults [1] however understanding is limited by variation in instrumentation, testing
protocols, and mediating factors [2].
Results • Task-dependent VS impairment was seen in PD (Table 1). • A wide range of instruments and outcome measures were reported in the 15 articles and were task-relevant (Table 1). • Temporal resolutions were lower (50 - 60 Hz) for mobile devices compared to static devices (1000 Hz), impacting on precision and accuracy of outcomes. • Instrument reliability and validity was insufficiently reported in all studies, and few considered mediators of VS such as visual or cognitive deficits which are common in PD. Table 1 Visual outcome measures and real-world activities Saccade
Aim
Fixation
Visual sampling
Visual Outcome
• Examine the literature concerning measurement of VS during realworld activities in PD to inform robust protocol development.
Saccades and Fixations Velocity
Direction Duration
Frequency
Latency
Amplitude
Duration
Frequency
Motor Task
Frequency
Duration
(↑)
(-)
(↑)
(↓)
NR
(↑)
NR
NR
(↓)
(↓)
NR
NR
NR
NR
NR
NR
NR
NR
(↓)
(↓)
Turning in place
(↓)
NR
NR
(↑)
(↓)
(↓)
NR
NR
NR
NR
Medline, Embase, PsychInfo, Scopus, Web of Knowledge, PubMed
Upper-limb tasks
(↓)
NR
(↑)
NR
(↑)
(↓)
NR
NR
NR
NR
and the Cochrane library databases were searched. Two independent
Driving
NR
NR
NR
NR
NR
NR
NR
(↓)
(↓)
NR
reviewers and an adjudicator screened articles that described
[✓= Reported outcome for both PD and HC, NR denotes not reported, ‘↓‘ indicates PD subjects less than HC, ‘↑’ indicates PD subjects more than HC, ‘-‘ indicates no difference between PD and HC]
Walking
Methods
quantitative VS in healthy controls (HC) and PD.
Obstacle crossing
Conclusions and Recommendations
References
• Future research is required to accurately characterise VS impairments in PD
1. Galna S et al. Visual sampling during walking in people with Parkinson’s disease and the influence of environment and dualtask. Brain Research. 1473(2012) 35-43.
during real-world activities. • Mobile eye-trackers provide the most comprehensive measurement. • Use task appropriate instrumentation to measure VS with temporal resolution ≥50Hz for saccade detection. • For saccade durations use a temporal resolution of ≥200Hz, which may involve combining devices. • Report reliability and validity of instrument used. • Define all visual outcomes and measure using a task-dependent or adaptable algorithm. Figure 1 PRISMA flow chart of study design
• Routinely assess and control for basic visual function and cognition.
Presented at the International Society of Posture and Gait Research World Congress, Vancouver, Canada, 2014
2. Stuart S et al. (2014) 'The measurement of visual sampling during real-world activity in Parkinson's disease and healthy controls: A structured literature review', J Neurosci Methods, 222, pp. 17588.
Acknowledgements The Research was supported/funded by the National Institute for Health Research (NIHR) Newcastle Biomedical Research Unit based at Newcastle Hospitals NHS Foundation Trust and Newcastle University. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.
