Quantifying saccades while walking: Validity of a novel velocity-based algorithm for mobile eye tracking

Stuart, Samuel; Galna, Brook; Lord, Sue; Rochester, Lynn; Godfrey, Alan

doi:10.1109/embc.2014.6944931

Cited by 28 publications

(63 citation statements)

References 16 publications

(28 reference statements)

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“…For example, static seated eye-movement assessments tended to comprehensively report many outcomes from long testing protocols, whereas dynamic standing or walking tasks tended to report a small number of largely saccadic outcomes (e.g., saccade number, velocity, amplitude; Murray et al, 2014Murray et al, , 2017Stuart et al, 2019b). This task-dependent reporting of eye-movement outcomes likely stems from the complexity of data processing and analysis with increasingly dynamic tasks (Zhu and Ji, 2005;Stuart et al, 2014bStuart et al, , 2019a. Unlike controlled static seated assessments, dynamic tasks introduce other factors (e.g., head movement, vestibular-ocular reflexes, lighting conditions of testing) that can impact recordings and need to be controlled for as these factors have been demonstrated to influence eye-tracking outcomes (Stuart et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

The Measurement of Eye Movements in Mild Traumatic Brain Injury: A Structured Review of an Emerging Area

Stuart

Parrington

Martini

et al. 2020

Front. Sports Act. Living

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Mild traumatic brain injury (mTBI), or concussion, occurs following a direct or indirect force to the head that causes a change in brain function. Many neurological signs and symptoms of mTBI can be subtle and transient, and some can persist beyond the usual recovery timeframe, such as balance, cognitive or sensory disturbance that may pre-dispose to further injury in the future. There is currently no accepted definition or diagnostic criteria for mTBI and therefore no single assessment has been developed or accepted as being able to identify those with an mTBI. Eye-movement assessment may be useful, as specific eye-movements and their metrics can be attributed to specific brain regions or functions, and eye-movement involves a multitude of brain regions. Recently, research has focused on quantitative eye-movement assessments using eye-tracking technology for diagnosis and monitoring symptoms of an mTBI. However, the approaches taken to objectively measure eye-movements varies with respect to instrumentation, protocols and recognition of factors that may influence results, such as cognitive function or basic visual function. This review aimed to examine previous work that has measured eye-movements within those with mTBI to inform the development of robust or standardized testing protocols. Medline/PubMed, CINAHL, PsychInfo and Scopus databases were searched. Twenty-two articles met inclusion/exclusion criteria and were reviewed, which examined saccades, smooth pursuits, fixations and nystagmus in mTBI compared to controls. Current methodologies for data collection, analysis and interpretation from eye-tracking technology in individuals following an mTBI are discussed. In brief, a wide range of eye-movement instruments and outcome measures were reported, but validity and reliability of devices and metrics were insufficiently reported across studies. Interpretation of outcomes was complicated by poor study reporting of demographics, mTBI-related features (e.g., time since injury), and few studies considered the influence that cognitive or visual functions may have on eye-movements. The reviewed evidence suggests that eye-movements are impaired in mTBI, but future research is required to accurately Stuart et al. Measurement of Eye-Movements in mTBI and robustly establish findings. Standardization and reporting of eye-movement instruments, data collection procedures, processing algorithms and analysis methods are required. Recommendations also include comprehensive reporting of demographics, mTBI-related features, and confounding variables.

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Section: Discussionmentioning

confidence: 99%

The Measurement of Eye Movements in Mild Traumatic Brain Injury: A Structured Review of an Emerging Area

Stuart

Parrington

Martini

et al. 2020

Front. Sports Act. Living

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“…The primary behavioural outcome of this study was saccade frequency (number of saccades per second) during gait, obtained from the raw mobile eye‐tracker data (Fig. C) using a previously validated algorithm (Stuart et al ., ). Only saccades with ≥ 5° amplitude (≥ 240°/s) were analysed to account for vestibular‐ocular reflex or micro‐saccade data intrusion (Galna et al ., ; Stuart et al ., ), and a maximal velocity threshold of ≥ 1000°/s was used to rule out flickers or other spurious movements.…”

Section: Methodsmentioning

confidence: 97%

“…C) using a previously validated algorithm (Stuart et al ., ). Only saccades with ≥ 5° amplitude (≥ 240°/s) were analysed to account for vestibular‐ocular reflex or micro‐saccade data intrusion (Galna et al ., ; Stuart et al ., ), and a maximal velocity threshold of ≥ 1000°/s was used to rule out flickers or other spurious movements. Saccade frequency was calculated as the number of saccades made within a walk divided by the duration of the walk, which controlled for the different walking speeds between participants in the same manner as previous research (Galna et al ., ).…”

Section: Methodsmentioning

confidence: 97%

Direct and indirect effects of attention and visual function on gait impairment in Parkinson's disease: influence of task and turning

Stuart

Galna

Delicato

et al. 2017

Eur J of Neuroscience

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Gait impairment is a core feature of Parkinson's disease (PD) which has been linked to cognitive and visual deficits, but interactions between these features are poorly understood. Monitoring saccades allows investigation of real-time cognitive and visual processes and their impact on gait when walking. This study explored: (i) saccade frequency when walking under different attentional manipulations of turning and dual-task; and (ii) direct and indirect relationships between saccades, gait impairment, vision and attention. Saccade frequency (number of fast eye movements per-second) was measured during gait in 60 PD and 40 agematched control participants using a mobile eye-tracker. Saccade frequency was significantly reduced in PD compared to controls during all conditions. However, saccade frequency increased with a turn and decreased under dual-task for both groups. Poorer attention directly related to saccade frequency, visual function and gait impairment in PD, but not controls. Saccade frequency did not directly relate to gait in PD, but did in controls. Instead, saccade frequency and visual function deficit indirectly impacted gait impairment in PD, which was underpinned by their relationship with attention. In conclusion, our results suggest a vital role for attention with direct and indirect influences on gait impairment in PD. Attention directly impacted saccade frequency, visual function and gait impairment in PD, with connotations for falls. It also underpinned indirect impact of visual and saccadic impairment on gait. Attention therefore represents a key therapeutic target that should be considered in future research.

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“…Video Inspection: Videos were analysed similar to previous work [14]. All IR videos (eye/fieldcamera) for each participant (n=20) during static and dynamic trials were visually inspected by a single examiner (AH) frame-by-frame, in order to compare algorithm results (180 videos in total).…”

Section: Feature Selection and Evaluationmentioning

confidence: 99%

iTrack: instrumented mobile electrooculography (EOG) eye-tracking in older adults and Parkinson’s disease

et al. 2016

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Detection of saccades (fast eye-movements) within raw mobile electrooculography (EOG) data involves complex algorithms which typically process data acquired during seated static tasks only. Processing of data during dynamic tasks such as walking is relatively rare and complex, particularly in older adults or people with Parkinson's disease (PD). Development of algorithms that can be easily implemented to detect saccades is required. This study aimed to develop an algorithm for the detection and measurement of saccades in EOG data during static (sitting) and dynamic (walking) tasks, in older adults and PD. Eye-tracking via mobile EOG and infra-red (IR) eye-tracker (with video) was performed with a group of older adults (n = 10) and PD participants (n = 10) (⩾50 years). Horizontal saccades made between targets set 5°, 10° and 15° apart were first measured while seated. Horizontal saccades were then measured while a participant walked and executed a 40° turn left and right. The EOG algorithm was evaluated by comparing the number of correct saccade detections and agreement (ICC) between output from visual inspection of eye-tracker videos and IR eye-tracker. The EOG algorithm detected 75-92% of saccades compared to video inspection and IR output during static testing, with fair to excellent agreement (ICC 0.49-0.93). However, during walking EOG saccade detection reduced to 42-88% compared to video inspection or IR output, with poor to excellent (ICC 0.13-0.88) agreement between methodologies. The algorithm was robust during seated testing but less so during walking, which was likely due to increased measurement and analysis error with a dynamic task. Future studies may consider a combination of EOG and IR for comprehensive measurement.

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Quantifying saccades while walking: Validity of a novel velocity-based algorithm for mobile eye tracking

Cited by 28 publications

References 16 publications

The Measurement of Eye Movements in Mild Traumatic Brain Injury: A Structured Review of an Emerging Area

The Measurement of Eye Movements in Mild Traumatic Brain Injury: A Structured Review of an Emerging Area

Direct and indirect effects of attention and visual function on gait impairment in Parkinson's disease: influence of task and turning

iTrack: instrumented mobile electrooculography (EOG) eye-tracking in older adults and Parkinson’s disease

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