title: Accuracy and re-test reliability of mobile eye-tracking in Parkinson's disease and older adults.
abstract: Mobile eye-tracking is important for understanding the role of vision during real-world tasks in older adults (OA) and people with Parkinson's disease (PD). However, accuracy and reliability of such devices have not been established in these populations. We used a novel protocol to quantify accuracy and reliability of a mobile eye-tracker in OA and PD. A mobile eye-tracker (Dikablis) measured the saccade amplitudes of 20 OA and 14 PD on two occasions. Participants made saccades between targets placed 5°, 10° and 15° apart. Impact of visual correction (glasses) on saccadic amplitude measurement was also investigated in 10 OA. Saccade amplitude accuracy (median bias) was -1.21° but a wide range of bias (-7.73° to 5.81°) was seen in OA and PD, with large vertical saccades (15°) being least accurate. Reliability assessment showed a median difference between sessions of <1° for both groups, with poor to good relative agreement (Spearman rho: 0.14 to 0.85). Greater accuracy and reliability was observed in people without visual correction. Saccade amplitude can be measured with variable accuracy and reliability using a mobile eye-tracker in OA and PD. Human, technological and study-specific protocol factors may introduce error and are discussed along with methodological recommendations.
authors.affiliation: Institute of Neuroscience/Newcastle University Institute for Ageing, Clinical Ageing Research Unit, Newcastle University, United Kingdom. Electronic address: sam.stuart@newcastle.ac.uk.
authors.forename: S
authors.initials: S
authors.lastname: Stuart
authors.affiliation: Institute of Neuroscience/Newcastle University Institute for Ageing, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: L
authors.initials: L
authors.lastname: Alcock
authors.affiliation: Institute of Neuroscience/Newcastle University Institute for Ageing, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Godfrey
authors.affiliation: Institute of Neuroscience/Newcastle University Institute for Ageing, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Lord
authors.affiliation: Institute of Neuroscience/Newcastle University Institute for Ageing, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: L
authors.initials: L
authors.lastname: Rochester
authors.affiliation: Institute of Neuroscience/Newcastle University Institute for Ageing, Clinical Ageing Research Unit, Newcastle University, United Kingdom.
authors.forename: B
authors.initials: B
authors.lastname: Galna
mesh_terms: D000368:Aged; D005260:Female; D006257:Head / Q000503:physiopathology; D006801:Humans; D008297:Male; D010300:Parkinson Disease / Q000503:physiopathology*; D015203:Reproducibility of Results; D012438:Saccades; D014796:Visual Perception
keywords: Accuracy; Mobile eye-tracking; Parkinson's disease; Reliability; Saccades; Walking