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Visual sampling in Parkinson’s disease: current methodological issues

Lookup NU author(s): Dr Sam Stuart, Dr Lisa Alcock, Dr Brook Galna, Dr Susan Lord, Professor Lynn Rochester

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Abstract

Background: Visual sampling (VS) is described by the combination of fixations and saccades required to gather information about the environment when completing a task. VS measurement is used to investigate the complex role of vision during real-world activities in Parkinson’s disease (PD). Earlier research is limited to static simple motor tasks (e.g. button pressing or mouse clicks) or measurement of VS alone via computer testing, but more recent investigations involve VS measurement during real-world activities (e.g. walking, driving, obstacle crossing etc.). However, there remains no gold standard for the measurement or reporting of VS during such activities. Accordingly, the objective measurement of VS varies with respect to instrumentation, testing protocols, and mediating factors that may influence VS. Aim: The aim of this review was to examine previous literature measuring VS during real-world activities in PD to inform the development of robust protocols. Within this review a real-world activity was considered to be a goal-orientated motor task involving more than one body segment (e.g. reaching or walking). Methods: Medline, Embase, PsychInfo, Scopus, Web of Knowledge, PubMed and the Cochrane library databases were searched. Two independent reviewers and an adjudicator screened articles that described quantitative VS in healthy controls and PD. Results: Twenty full-text articles were screened and 15 met the inclusion/exclusion criteria. A wide range of instruments (i.e. electro-oculography; n=7, head-mounted eye-trackers; n=5, desk-mounted eye-trackers; n=1, and 2D video capture; n=2) and outcome measures were reported which were generally used in a task-dependent manner. Temporal resolutions were lower (50 – 60 Hz) for devices that allow mobility compared to static VS devices (1000 Hz), which impacts on precision and accuracy of outcomes tested. Instrument reliability and validity was insufficiently reported across all studies, and few considered mediators of VS such as visual or cognitive deficits which are common in PD. Conclusions: Future research is required to accurately characterise VS impairments in PD during real-world activities. No single measurement or combination of measurements has been identified as the most informative indicator of these processes. Although mobile eye-trackers provide the most comprehensive measurement to date, the validity and reliability of using such devices during real-world activities in older adults or PD has yet to be determined. To aid the development of more robust protocols we propose a series of recommendations for future VS research protocols, such as the use of ≥50Hz devices for saccade detection and the routine assessment of visual and cognitive impairments.


Publication metadata

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 for Posture & Gait Research

URL: http://ispgr.org/cpages/conferences


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