title: The measurement of visual sampling during real-world activity in Parkinson's disease and healthy controls: a structured literature review.
abstract: BACKGROUND
  Visual sampling techniques are used to investigate the complex role of vision during real-world activities in Parkinson's disease. Earlier research is limited to static simple tasks or measurement of eye movements alone, but more recent investigations involve more real-world activities. The approach to the objective measurement of eye movements varies with respect to instrumentation, testing protocols, and mediating factors that may influence visual sampling.
  
  
  OBJECTIVE
  The aim of this review was to examine previous work measuring visual sampling during real-world activities in Parkinson's disease 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 such as 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 visual sampling in people with Parkinson's disease and healthy controls.
  
  
  RESULTS
  Twenty full-text articles were screened and 15 met inclusion/exclusion criteria. A wide range of instruments and outcome measures were reported which were generally used in a task-dependent manner. Instrument reliability and validity was insufficiently reported in all studies. Few studies considered mediators of visual sampling such as visual or cognitive deficits.
  
  
  CONCLUSIONS
  Future research is required to accurately characterise visual impairments in Parkinson's disease and during real-world activities. Composite use of instruments may be required to achieve reliability and validity of visual sampling outcomes which need to be standardised. Recommendations also include assessment of cognition and basic visual function.
authors.affiliation: Institute for Ageing and Health, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: Samuel
authors.initials: S
authors.lastname: Stuart
authors.affiliation: Institute for Ageing and Health, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: Lisa
authors.initials: L
authors.lastname: Alcock
authors.affiliation: Institute for Ageing and Health, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: Brook
authors.initials: B
authors.lastname: Galna
authors.affiliation: Institute for Ageing and Health, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: Sue
authors.initials: S
authors.lastname: Lord
authors.affiliation: Institute for Ageing and Health, Clinical Ageing Research Unit, Newcastle University, United Kingdom. Electronic address: lynn.rochester@newcastle.ac.uk.
authors.forename: Lynn
authors.initials: L
authors.lastname: Rochester
mesh_terms: D053483:Eye Movement Measurements / Q000295:instrumentation; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D009043:Motor Activity; D010300:Parkinson Disease / Q000503:physiopathology*
keywords: Eye movements; Eye-tracking; Motor task; Parkinson's disease; Vision; Visual sampling