Will eye tracking change the way we diagnose and classify concussion and structural brain injury?

Acute Eye-Tracking Changes Correlated With Vestibular Symptom Provocation Following Mild Traumatic Brain Injury

OBJECTIVES

To quantify norms and changes in eye-tracking proficiency, and determine vestibular symptom correlations in varsity college athletes following acute mild traumatic brain injury (mTBI). We hypothesized that mTBI impacts central coordination between the vestibular and oculomotor systems with resultant changes in eye-tracking proficiency that are correlated with vestibular symptom provocation.

DESIGN

Retrospective cohort study.

SETTING

Sports medicine care at a single institution.

PATIENTS

One hundred and nineteen college athletes diagnosed with mTBI by a physician between 2013 and 2019.

INTERVENTIONS

N/A.

MAIN OUTCOME MEASURES

Standard deviation of tangential error, standard deviation of radian error, mean phase error, and horizontal gain from virtual reality-based, circular eye-tracking goggles used at baseline and within 72 hours post-mTBI. Headache, dizziness, nausea, and fogginess provocation after the Vestibular Ocular Motor Screening (VOMS) smooth pursuits subtest compared with pretest baseline, assessed within 72 hours post-mTBI.

RESULTS

One hundred and nineteen college athletes (N = 56 women and 63 men) aged 18 to 24 years sustained a total of 177 mTBI. Forty-four percent of athletes displayed abnormal eye-tracking on at least 1 eye-tracking measure following acute mTBI compared with their baseline. From the VOMS, horizontal gain showed medium-sized to large-sized positive correlations with headache ( r = 0.34) and dizziness ( r = 0.54), respectively. Mean phase error showed a medium-sized negative correlation with nausea ( r = -0.32) on the VOMS.

CONCLUSIONS

Eye-tracking proficiency was impaired and correlated with vestibular symptom provocation following acute mTBI in college athletes. Future research should examine eye-tracking proficiency testing in other acute care settings to support mTBI diagnosis.

Eye-tracking paradigms for the assessment of mild cognitive impairment: a systematic review

Mild cognitive impairment (MCI), representing the 'transitional zone' between normal cognition and dementia, has become a novel topic in clinical research. Although early detection is crucial, it remains logistically challenging at the same time. While traditional pen-and-paper tests require in-depth training to ensure standardized administration and accurate interpretation of findings, significant technological advancements are leading to the development of procedures for the early detection of Alzheimer's disease (AD) and facilitating the diagnostic process. Some of the diagnostic protocols, however, show significant limitations that hamper their widespread adoption. Concerns about the social and economic implications of the increasing incidence of AD underline the need for reliable, non-invasive, cost-effective, and timely cognitive scoring methodologies. For instance, modern clinical studies report significant oculomotor impairments among patients with MCI, who perform poorly in visual paired-comparison tasks by ascribing less attentional resources to novel stimuli. To accelerate the Global Action Plan on the Public Health Response to Dementia 2017-2025, this work provides an overview of research on saccadic and exploratory eye-movement deficits among older adults with MCI. The review protocol was drafted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Electronic databases were systematically searched to identify peer-reviewed articles published between 2017 and 2022 that examined visual processing in older adults with MCI and reported gaze parameters as potential biomarkers. Moreover, following the contemporary trend for remote healthcare technologies, we reviewed studies that implemented non-commercial eye-tracking instrumentation in order to detect information processing impairments among the MCI population. Based on the gathered literature, eye-tracking-based paradigms may ameliorate the screening limitations of traditional cognitive assessments and contribute to early AD detection. However, in order to translate the findings pertaining to abnormal gaze behavior into clinical applications, it is imperative to conduct longitudinal investigations in both laboratory-based and ecologically valid settings.

Eye tracking for classification of concussion in adults and pediatrics

Introduction

In order to obtain FDA Marketing Authorization for aid in the diagnosis of concussion, an eye tracking study in an intended use population was conducted.

Methods

Potentially concussed subjects recruited in emergency department and concussion clinic settings prospectively underwent eye tracking and a subset of the Sport Concussion Assessment Tool 3 at 6 sites. The results of an eye tracking-based classifier model were then validated against a pre-specified algorithm with a cutoff for concussed vs. non-concussed. The sensitivity and specificity of eye tracking were calculated after plotting of the receiver operating characteristic curve and calculation of the AUC (area under curve).

Results

When concussion is defined by SCAT3 subsets, the sensitivity and specificity of an eye tracking algorithm was 80.4 and 66.1%, The AUC was 0.718. The misclassification rate (n = 282) was 31.6%.

Conclusion

A pre-specified algorithm and cutoff for diagnosis of concussion vs. non-concussion has a sensitivity and specificity that is useful as a baseline-free aid in diagnosis of concussion. Eye tracking has potential to serve as an objective “gold-standard” for detection of neurophysiologic disruption due to brain injury.

Consequences of inequity in the neurosurgical workforce: Lessons from traumatic brain injury

Women and minorities leave or fail to advance in the neurosurgical workforce more frequently than white men at all levels from residency to academia. The consequences of this inequity are most profound in fields such as traumatic brain injury (TBI), which lacks objective measures. We evaluated published articles on TBI clinical research and found that TBI primary investigators or corresponding authors were 86·5% White and 59·5% male. First authors from the resulting publications were 92.6% white. Most study participants were male (68%). 64·4% of NIH-funded TBI clinical trials did not report or recruit any black subjects and this number was even higher for other races and the Hispanic ethnicity. We propose several measures for mitigation of the consequences of the inequitable workforce in traumatic brain injury that could potentially contribute to more equitable outcomes. The most immediately feasible of these is validation and establishment of objective measures for triage and prognostication that are less susceptible to bias than current protocols. We call for incorporation of gender and race neutral metrics for TBI evaluation to standardize classification of injury. We offer insights into how socioeconomic factors contribute to increased death rates from women and minority groups. We propose the need to study how these disparities are caused by unfair health insurance reimbursement practices. Surgical and clinical research inequities have dire consequences, and until those inequities can be corrected, mitigation of those consequences requires system wide change.

Tracking-Based Interactive Assessment of Saccades, Pursuits, Visual Field, and Contrast Sensitivity in Children With Brain Injury

Visual deficits in children that result from brain injury, including cerebral/cortical visual impairment (CVI), are difficult to assess through conventional methods due to their frequent co-occurrence with cognitive and communicative disabilities. Such impairments hence often go undiagnosed or are only determined through subjective evaluations of gaze-based reactions to different forms, colors, and movements, which limits any potential for remediation. Here, we describe a novel approach to grading visual health based on eye movements and evidence from gaze-based tracking behaviors. Our approach—the “Visual Ladder”—reduces reliance on the user’s ability to attend and communicate. The Visual Ladder produces metrics that quantify spontaneous saccades and pursuits, assess visual field responsiveness, and grade spatial visual function from tracking responses to moving stimuli. We used the Ladder to assess fourteen hospitalized children aged 3 to 18 years with a diverse range of visual impairments and causes of brain injury. Four children were excluded from analysis due to incompatibility with the eye tracker (e.g., due to severe strabismus). The remaining ten children—including five non-verbal children—were tested multiple times over periods ranging from 2 weeks to 9 months, and all produced interpretable outcomes on at least three of the five visual tasks. The results suggest that our assessment tasks are viable in non-communicative children, provided their eyes can be tracked, and hence are promising tools for use in a larger clinical study. We highlight and discuss informative outcomes exhibited by each child, including directional biases in eye movements, pathological nystagmus, visual field asymmetries, and contrast sensitivity deficits. Our findings indicate that these methodologies will enable the rapid, objective classification and grading of visual impairments in children with CVI, including non-verbal children who are currently precluded from most vision assessments. This would provide a much-needed differential diagnostic and prognostic tool for CVI and other impairments of the visual system, both ocular and cerebral.

Classification of Comprehensive Neuro-Ophthalmologic Measures of Postacute Concussion

IMPORTANCE

Symptom-based methods of concussion diagnosis in contact sports result in underdiagnosis and repeated head injury exposure, increasing the risk of long-term disability. Measures of neuro-ophthalmologic (NO) function have the potential to serve as objective aids, but their diagnostic utility is unknown.

OBJECTIVE

To identify NO measures that accurately differentiate athletes with and without concussion.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was conducted among athletes with and without concussion who were aged 17 to 22 years between 2016 and 2017. Eye movements and cognitive function were measured a median of 19 days after injury among patients who had an injury meeting the study definition of concussion while playing a sport (retrospectively selected from a concussion clinic), then compared with a control group of participants without concussion (enrolled from 104 noncontact collegiate athlete volunteers without prior head injury). Data analysis was conducted from November 2019 through May 2020.

EXPOSURE

Concussion.

MAIN OUTCOMES AND MEASURES

Classification accuracy of clinically important discriminator eye-tracking (ET) metrics. Participants' eye movements were evaluated with a 12-minute ET procedure, yielding 42 metrics related to smooth pursuit eye movement (SPEM), saccades, dynamic visual acuity, and reaction time. Clinically important discriminator metrics were defined as those with significantly different group differences and area under the receiver operator characteristic curves (AUROCs) of at least 0.70.

RESULTS

A total of 34 participants with concussions (mean [SD] age, 19.7 [2.4] years; 20 [63%] men) and 54 participants without concussions (mean [SD] age, 20.8 [2.2] years; 31 [57%] men) completed the study. Six ET metrics (ie, simple reaction time, discriminate reaction time, discriminate visual reaction speed, choice visual reaction speed, and reaction time on 2 measures of dynamic visual acuity 2) were found to be clinically important; all were measures of reaction time, and none were related to SPEM. Combined, these 6 metrics had an AUROC of 0.90 (95% CI, 0.80-0.99), a sensitivity of 77.8%, and a specificity of 92.6%. The 6 metrics remained significant on sensitivity testing.

CONCLUSIONS AND RELEVANCE

In this study, ET measures of slowed visual reaction time had high classification accuracy for concussion. Accurate, objective measures of NO function have the potential to improve concussion recognition and reduce the disability associated with underdiagnosis.

Accelerating eye movement research via accurate and affordable smartphone eye tracking

Eye tracking has been widely used for decades in vision research, language and usability. However, most prior research has focused on large desktop displays using specialized eye trackers that are expensive and cannot scale. Little is known about eye movement behavior on phones, despite their pervasiveness and large amount of time spent. We leverage machine learning to demonstrate accurate smartphone-based eye tracking without any additional hardware. We show that the accuracy of our method is comparable to state-of-the-art mobile eye trackers that are 100x more expensive. Using data from over 100 opted-in users, we replicate key findings from previous eye movement research on oculomotor tasks and saliency analyses during natural image viewing. In addition, we demonstrate the utility of smartphone-based gaze for detecting reading comprehension difficulty. Our results show the potential for scaling eye movement research by orders-of-magnitude to thousands of participants (with explicit consent), enabling advances in vision research, accessibility and healthcare.

Eye Tracking as a Biomarker for Concussion in Children

OBJECTIVE

Concussion is the most common type of brain injury in both pediatric and adult populations and can potentially result in persistent postconcussion symptoms. Objective assessment of physiologic "mild" traumatic brain injury in concussion patients remains challenging. This study evaluates an automated eye-tracking algorithm as a biomarker for concussion as defined by its symptoms and the clinical signs of convergence insufficiency and accommodation dysfunction in a pediatric population.

DESIGN

Cross-sectional case-control study.

SETTING

Primary care.

PATIENTS

Concussed children (N = 56; mean age = 13 years), evaluated at a mean of 22-week post-injury, compared with 83 uninjured controls.

INDEPENDENT VARIABLES

Metrics comparing velocity and conjugacy of eye movements over time were obtained and were compared with the correlation between Acute Concussion Evaluation (ACE) scores, convergence, and accommodation dysfunction.

MAIN OUTCOME MEASURES

Subjects' eye movements recorded with an automated eye tracker while they watched a 220-second cartoon film clip played continuously while moving within an aperture.

RESULTS

Twelve eye-tracking metrics were significantly different between concussed and nonconcussed children. A model to classify concussion as diagnosed by its symptoms assessed using the ACE achieved an area under the curve (AUC) = 0.854 (71.9% sensitivity, 84.4% specificity, a cross-validated AUC = 0.789). An eye-tracking model built to identify near point of convergence (NPC) disability achieved 95.8% specificity and 57.1% sensitivity for an AUC = 0.810. Reduced binocular amplitude of accommodation had a Spearman correlation of 0.752(P value <0.001) with NPC.

CONCLUSION

Eye tracking correlated with concussion symptoms and detected convergence and accommodative abnormalities associated with concussion in the pediatric population. It demonstrates utility as a rapid, objective, noninvasive aid in the diagnosis of concussion.

Correlation between Ocular and Vestibular Abnormalities and Convergence Insufficiency in Post-Concussion Syndrome

The vestibular and oculomotor/visual systems are commonly affected in post-concussion syndrome (PCS). Convergence insufficiency (CI) is the most common ocular abnormality after concussion. Electrovestibulography (EVestG) is a relatively new non-invasive method that measures the peripheral vestibular responses; it has shown abnormal vestibular responses in a PCS. Here, we report the results of investigating the correlation between the vestibular and oculomotor systems in PCS population using EVestG and CI measures. Forty-eight PCS patients were tested using EVestG, out of which 20 also completed the Rivermead post-concussion questionnaire (RPQ). An EVestG feature (Field Potential (FP)-area) was extracted from the stationary part of the EVestG signals. A neuro-ophthalmologist (author BM) measured participants' CI at near vision using cross-cover examination and a prism-bar. Results indicate: (1) vestibular abnormality (i.e. FP-area) and CI values are significantly correlated in PCS (R = 0.68, p < .01), and (2) there are significant correlations between severity of concussion (i.e. RPQ3) and CI (R = 0.70, p < .01) and between RPQ3 and FP-area (R = -0.56, p < .02). To the best of our knowledge, this is the first study that objectively demonstrates a significant positive correlation between the CI and vestibular systems' abnormality. These findings are scientifically important as they help localise the pathology of PCS, and are clinically valuable as they help physicians in their decision-making about PCS diagnosis and rehabilitation strategies.

Aging and eye tracking: in the quest for objective biomarkers

Recent applications of eye tracking for diagnosis, prognosis and follow-up of therapy in age-related neurological or psychological deficits have been reviewed. The review is focused on active aging, neurodegeneration and cognitive impairments. The potential impacts and current limitations of using characterizing features of eye movements and pupillary responses (oculometrics) as objective biomarkers in the context of aging are discussed. A closer look into the findings, especially with respect to cognitive impairments, suggests that eye tracking is an invaluable technique to study hidden aspects of aging that have not been revealed using any other noninvasive tool. Future research should involve a wider variety of oculometrics, in addition to saccadic metrics and pupillary responses, including nonlinear and combinatorial features as well as blink- and fixation-related metrics to develop biomarkers to trace age-related irregularities associated with cognitive and neural deficits.

Vergence Endurance Test: A Pilot Study for a Concussion Biomarker

The Vergence Endurance Test (VET), a quantitative and objective eye movement assessment, was utilized to differentiate control from concussed subjects. Nine symptomatic concussed (2 male; 30.8 ± 11 years) and 9 asymptomatic control (6 male; 25.1 ± 1.4 years) subjects participated in the VET. Symmetrical disparity vergence step targets were presented with and without visual distractors. A masked data analyst measured vergence latency, peak velocity, response amplitude, settling time, and the percentage of trials which contained blinks. A Binocular Precision Index (BPI) and a Binocular Accuracy Index (BAI) were calculated to quantify the changes that occur in the vergence parameters over the duration of the VET. Convergence and divergence peak velocity, divergence response amplitude, the percentage of trials that contained blinks during the transient portion of the response, and the BAI were significantly (p < 0.05) different between the concussed and the control subjects. For these parameters, the BAI and divergence response amplitude yielded the greatest accuracy, 78%, in their ability to discriminate between the groups. The VET objectively measures the change in vergence performance over time and shows promise as a method to diagnose a concussion. Future studies will determine whether the VET can be used to assess the extent of natural recovery and the effectiveness of therapeutic interventions.

Objective Eye Tracking Deficits Following Concussion for Youth Seen in a Sports Medicine Setting

Quantification of visual deficits may help to identify dysfunction following concussion. We evaluated eye-tracking measurements among adolescents within 10 days of concussion and healthy control participants. Patients who reported to 2 tertiary care sport concussion clinics within 10 days of concussion completed an objective eye tracking assessment. Seventy-nine participants completed the study, 44 with concussion (mean age = 14.1 ± 2.2 years, 39% female) and 35 controls (mean age = 14.3 ± 2.4 years, 57% female). Right eye skew along the bottom of the screen was significantly higher for the concussion group compared to controls (median = 0.022 [interquartile range = -0.263, 0.482] vs 0.377 [interquartile range = -0.574, -0.031]; P = .002), but not the left eye. Among the variables investigated, right eye skew was altered for adolescents with a concussion. Visual function is an important component in the postconcussion evaluation, and identifying deficits soon after injury may allow for earlier specialist referral and intervention.

Brain Monitoring Devices in Neuroscience Clinical Research: The Potential of Remote Monitoring Using Sensors, Wearables, and Mobile Devices

The increasing miniaturization and affordability of sensors and circuitry has led to the current level of innovation in the area of wearable and microsensor solutions for health monitoring. This facilitates the development of solutions that can be used to measure complex health outcomes in nonspecialist and remote settings. In this article, we review a number of innovations related to brain monitoring including portable and wearable solutions to directly measure brain electrical activity, and solutions measuring aspects related to brain function such as sleep patterns, gait, cognition, voice acoustics, and gaze analysis. Despite the need for more scientific validation work, we conclude that there is enough understanding of how to implement these approaches as exploratory tools that may provide additional valuable insights due to the rich and frequent data they produce, to justify their inclusion in clinical study protocols.