Long-Term Effects of Low-Level Blast Exposure and High-Caliber Weapons Use in Military Special Operators.

Chronic low-level blast exposure has been linked with neurological alterations and traumatic brain injury (TBI) biomarkers. Impaired smooth-pursuit eye movements (SPEM) are often associated with TBI. The purpose of this study was to determine whether long-term operators of low-level blast exposure or high-caliber weapons use displayed oculomotor behaviors that differed from controls. Twenty-six members of an elite military unit performed a computerized oculomotor testing task using an eye tracker and completed a concussion assessment questionnaire. The participants were split into a blast exposure group and control group. The blast exposure group had a history of exposure to low-level blasts or high-caliber weapon use. The results revealed significant differences in SPEM, saccades, and fixations between the blast exposure group and control group. The blast exposure group's eye movements were slower, stopped at more frequent points when following a target, traveled further from the target in terms of both speed and direction, and showed higher rates of variation and inefficiency. Poor oculomotor behavior correlated with a higher symptom severity on the concussion assessment questionnaire. Military special operators exposed to long-term low-level blasts or high-caliber weapons usage displayed an impaired oculomotor behavior in comparison to controls. These findings further our understanding of the impact of long-term low-level blast exposure on the oculomotor behavior of military special operators and may inform practical implications for military training.

Smooth Pursuit Eye Movements as a Biomarker for Mild Concussion within 7-Days of Injury.

AIM: Deficits in smooth-pursuit eye movements (SPEM) are often associated with mild traumatic brain injury(TBI). Eye tracking tests serve as a quick objective clinical tool to assess such predictive visual tracking. In this study, SPEM was assessed along circular, horizontal and vertical trajectories in adolescents with concussion and age-matched controls. METHODS: Ninety-one young adolescents with concussion and 140 visually healthy age-matched controls with a mean age of 14 years performed a computerized test of circular, horizontal and vertical tracking task using an eye tracker. Oculomotor tracking was assessed by computing the rate of fixation, saccades and SPEM made while performing the tasks. RESULTS: The predictive visual tracking task was able to differentiate the TBI group from the non-TBI group. The TBI group showed a significant difference in the fixation, saccades and SPEM percentages for circular tracking movement compared to the controls. There was a significant difference in fixation and SPEM % for horizontal and vertical tracking. CONCLUSIONS: Predictive visual tracking, assessed using eye tracking technology, is able to differentiate deficits in oculomotor functions in individuals with and without concussion. The eye tracking technology may serve as a quick objective tool to detect and monitor neural deficits due to TBI.

The Pupillary Light Reflex as a Biomarker of Concussion.

The size of our pupils changes continuously in response to variations in ambient light levels, a process known as the pupillary light reflex (PLR). The PLR is not a simple reflex as its function is modulated by cognitive brain function and any long-term changes in brain function secondary to injury should cause a change in the parameters of the PLR. We performed a retrospective clinical review of the PLR of our patients using the BrightLamp Reflex iPhone app. The PLR variables of latency, maximum pupil diameter (MaxPD), minimum pupil diameter (MinPD), maximum constriction velocity (MCV), and the 75% recovery time (75% PRT) were associated with significant differences between subjects who had suffered a concussion and those that had not. There were also significant differences in PLR metrics over the life span and between genders and those subjects with and without symptoms. The differences in PLR metrics are modulated not only by concussion history but also by gender and whether or not the person has symptoms associated with a head injury. A concussive injury to the brain is associated with changes in the PLR that persist over the life span, representing biomarkers that might be used in clinical diagnosis, treatment, and decision making.

Brain Vital Signs in Elite Ice Hockey: Towards Characterizing Objective and Specific Neurophysiological Reference Values for Concussion Management.

Background: Prior concussion studies have shown that objective neurophysiological measures are sensitive to detecting concussive and subconcussive impairments in youth ice-hockey. These studies monitored brain vital signs at rink-side using a within-subjects design to demonstrate significant changes from pre-season baseline scans. However, practical clinical implementation must overcome inherent challenges related to any dependence on a baseline. This requires establishing the start of normative reference data sets. Methods: The current study collected specific reference data for N = 58 elite, youth, male ice-hockey players and compared these with a general reference dataset from N = 135 of males and females across the lifespan. The elite hockey players were recruited to a select training camp through CAA Hockey, a management agency for players drafted to leagues such as the National Hockey League (NHL). The statistical analysis included a test-retest comparison to establish reliability, and a multivariate analysis of covariance to evaluate differences in brain vital signs between groups with age as a covariate. Findings: Test-retest assessments for brain vital signs evoked potentials showed moderate-to-good reliability (Cronbach's Alpha > 0.7, Intraclass correlation coefficient > 0.5) in five out of six measures. The multivariate analysis of covariance showed no overall effect for group (p = 0.105), and a significant effect of age as a covariate was observed (p < 0.001). Adjusting for the effect of age, a significant difference was observed in the measure of N100 latency (p = 0.022) between elite hockey players and the heterogeneous control group. Interpretation: The findings support the concept that normative physiological data can be used in brain vital signs evaluation in athletes, and should additionally be stratified for age, skill level, and experience. These can be combined with general norms and/or individual baseline assessments where appropriate and/or possible. The current results allow for brain vital sign evaluation independent of baseline assessment, therefore enabling objective neurophysiological evaluation of concussion management and cognitive performance optimization in ice-hockey.

Oculomotor Training for Poor Saccades Improves Functional Vision Scores and Neurobehavioral Symptoms.

OBJECTIVES: To determine if participants with saccadic dysfunction improved after participating in a standardized oculomotor training program. A secondary objective was to accurately quantify change in saccades after training using eye tracking technology. A third objective was to examine patients' neurobehavioral symptoms before and after oculomotor training using the Neurobehavioral Symptom Inventory (NSI). DESIGN: A prospective study involving treatment and control group pre-post intervention design. SETTING: Data were collected in eye clinics with a standardized eye tracking equipment setup. PARTICIPANTS: Participants in the bottom 25th percentile for saccadic eye movements (N=92; intervention=46, control=46) who were currently asymptomatic of specific disorder. INTERVENTIONS: Participants were randomly assigned to the control or intervention group. The intervention group engaged in 10 minutes of oculomotor training daily for 5 days. MAIN OUTCOME MEASURES: The ratio of the peak saccadic velocity over its average velocity (the Q ratio), saccadic targeting, and NSI. RESULTS: Results revealed significant interactions between control and intervention groups (P=.013). The control group increased 7% from pre to post; however, the intervention group exhibited a 6% decreased from pre to post. Participants in the intervention group demonstrated a 25% improvement in targeting saccade accuracy (P=.021). Additionally, there was a significant reduction in all neurobehavioral factors on the NSI in the intervention group, specifically the affective and cognitive factors relating to poor saccades. CONCLUSIONS: For this population, oculomotor training (Q ratio and saccade accuracy) resulted improved saccadic metrics and a significant reduction in overall symptoms as shown on the NSI. Future participants reported improved symptoms pre- and postintervention. Further research is needed to understand saccadic performance and gaze stability during specific tasks (such as reading).

Fixation stability as a biomarker for differentiating mild traumatic brain injury from age matched controls in pediatrics.

OBJECTIVES: Traumatic brain injury (TBI) is an increasingly significant health concern worldwide, compounded by the difficultly in detection and diagnosis. Fortunately, a growing body of research has identified oculomotor behavior, specifically fixations, saccades and smooth pursuit eye movements as a promising endophenotype for neurotrauma. To date, limited research exists using fixation stability in a comparative study to indicate the presence of a mild TBI (mTBI), especially in the pediatric population. METHODS: The present study examined data from 91 individuals clinically diagnosed with mTBI and a further 140 age- and gender-matched controls. They all completed the RightEye fixation stability test using a remote eye tracker. Participants were compared on five fixation metrics: Bivariate Contour Ellipse Area (BCEA), Convergence Point, Depth, Disassociated Phoria, and Targeting Displacement. RESULTS: Results were analyzed using one-way univariate ANOVAs, ROC analysis, and stepwise logistic regression. BCEA results revealed significant differences between groups with the mTBI group showing a larger gaze spread, indicative of less ability to keep the eyes close to the target without deviating. CONCLUSIONS: Fixation stability is detrimentally impacted by mTBI in pediatric patients, and the oculomotor test can be used to differentiate between those with and without an mTBI.

Oculomotor Behavior Predict Professional Cricket Batting and Bowling Performance.

Importance: A new, shorter version of cricket was introduced recently (Twenty20; T20). Since its inception, T20 cricket has rapidly become a popular and exciting format of cricket. However, there is little understanding of factors such as visual-motor control that influence expert performance. Objective: The purpose of this project is to determine if a series of oculomotor measures can predict batting and bowling performance in professional cricket players. Design: This study used a cross-sectional design. Each participant took part in a suite of eye-tracking tests to measure oculomotor behavior compared to their performance data. Participants: This study used a sample of 59 male T20 league professional cricket players (30 Bowlers and 29 Batsman). Results: One-way univariate analyses of variance examined the differences in oculomotor behavior between batsman and bowlers. A series of multiple regression analyses was conducted to evaluate how well the visual variables predict bowling and batting performance variables. Results demonstrate that several oculomotor eye tracking measures were good predictors of run performance and strike rate, including sports total score, sports on-field score, and sports functional score. Likewise, several of the same metrics predicted Runs and Wicket performance for bowlers. Overall, results provided further validation to a growing body of literature supporting the use of eye-tracking technology in performance evaluation.

Head Position and Posturography: A Novel Biomarker to Identify Concussion Sufferers.

Balance control systems involve complex systems directing muscle activity to prevent internal and external influences that destabilize posture, especially when body positions change. The computerized dynamic posturography stability score has been established to be the most repeatable posturographic measure using variations of the modified Clinical Test of Sensory Integration in Balance (mCTSIB). However, the mCTSIB is a standard group of tests relying largely on eyes-open and -closed standing positions with the head in a neutral position, associated with probability of missing postural instabilities associated with head positions off the neutral plane. Postural stability scores are compromised with changes in head positions after concussion. The position of the head and neck induced by statically maintained head turns is associated with significantly lower stability scores than the standardized head neutral position of the mCTSIB in Post-Concussion Syndrome (PCS) subjects but not in normal healthy controls. This phenomenon may serve as a diagnostic biomarker to differentiate PCS subjects from normal ones as well as serving as a measurement with which to quantify function or the success or failure of a treatment. Head positions off the neutral plane provide novel biomarkers that identify and differentiate subjects suffering from PCS from healthy normal subjects.

Oculomotor Behavior as a Biomarker for Differentiating Pediatric Patients With Mild Traumatic Brain Injury and Age Matched Controls.

IMPORTANCE: Children have the highest incidence of mild traumatic brain injury (mTBI) in the United States. However, mTBI, specifically pediatric patients with mTBI, are notoriously difficult to detect, and with a reliance on traditional, subjective measurements of eye movements, the subtle but key oculomotor deficits are often missed. OBJECTIVE: The purpose of this project is to determine if the combined measurement of saccades, smooth pursuit, fixations and reaction time represent a biomarker for differentiating pediatric patients with mild traumatic brain injury compared to age matched controls. DESIGN: This study used cross-sectional design. Each participant took part in a suite of tests collectively labeled the "Brain Health EyeQ" to measure saccades, smooth pursuit, fixations and reaction time. PARTICIPANTS: The present study recruited 231 participants - 91 clinically diagnosed with a single incident mTBI in the last 2 days as assessed by both the Glasgow Coma Scale (GCS) and Graded Symptoms Checklist (GSC), and 140 age and gender-matched controls (n = 165 male, n = 66 female, M age = 14.20, SD = 2.78). RESULTS: One-way univariate analyses of variance examined the differences in performance on the tests between participants with mTBI and controls. ROC curve analysis examined the sensitivity and specificity of the tests. Results indicated that together, the "Brain Health EyeQ" tests were successfully able to identify participants with mTBI 75.3% of the time, providing further validation to a growing body of literature supporting the use of eye tracking technology for mTBI identification and diagnosis.

Vertical smooth pursuit as a diagnostic marker of traumatic brain injury.

AIM: Neural deficits were measured via the eye tracking of vertical smooth pursuit (VSP) as markers of traumatic brain injury (TBI). The present study evaluated the ability of the eye tracking tests to differentiate between different levels of TBI severity and healthy controls. METHODOLOGY: Ninety-two individuals divided into four groups (those with mild, moderate or severe TBI and healthy controls) participated in a computerized test of VSP eye movement using a remote eye tracker. RESULTS: The VSP eye tracking test was able to distinguish between severe and moderate levels of TBI but unable to detect differences in the performance of participants with mild TBI and healthy controls. CONCLUSION: The eye-tracking technology used to measure VSP eye movements is able to provide a timely and objective method of differentiating between individuals with moderate and severe levels of TBI.

Horizontal and vertical self-paced saccades as a diagnostic marker of traumatic brain injury.

AIM: Eye tracking tests to measure horizontal and vertical saccades as a proxy for neural deficits associated with traumatic brain injury (TBI) were evaluated in the present study. METHODOLOGY: A total of 287 participants reporting either no TBI, mild, moderate or severe TBI participated in a suite of eye tracking tests to measure horizontal and vertical saccadic performance. RESULTS: The horizontal saccades test offered a sensitivity of 0.77 and a specificity of 0.78, similarly the vertical saccades tests offered a sensitivity of 0.64 and a specificity of 0.65. CONCLUSION: The results indicated that using eye-tracking technology to measure these metrics offers an objective, reliable and quantifiable way of differentiating between individuals with different severities of TBI, and those without a TBI.

The Effect of Prior Tennis Experience on Wheelchair Tennis Players' Visual Search.

The purpose of this study was to examine whether prior biped tennis playing experience results in different visual search strategies compared with no prior biped playing experience. A total of 32 wheelchair (WC) tennis players, 17 males and 15 females, ranked between 1 and 16 on the International Tennis Federation rankings participated in this study. Half the players had prior experience playing tennis as a biped player, and half had no prior experience in biped tennis. The athletes viewed 18 different serves from an expert WC player while their gaze was monitored using eye tracking. Results revealed significant differences between the groups in fixation duration and number of fixations. Differences were also found in fixation locations and durations across biomechanical phases of the serve. The WC only players had more fixations for shorter periods than did WC with biped players in the ritual phase. In the preparatory and execution phases, however, the WC only players had fewer fixations for longer duration than the WC with biped players. Results are discussed in terms of long-term memory structures, learning, and considerations when coaching and training WC tennis players.

The Reliability, Validity, and Normative Data of Interpupillary Distance and Pupil Diameter Using Eye-Tracking Technology.

PURPOSE: The purpose of this study was to determine the reliability of interpupillary distance (IPD) and pupil diameter (PD) measures using an infrared eye tracker and central point stimuli. Validity of the test compared to known clinical tools was determined, and normative data was established against which individuals can measure themselves. METHODS: Participants (416) across various demographics were examined for normative data. Of these, 50 were examined for reliability and validity. Validity for IPD measured the test (RightEye IPD/PD) against the PL850 Pupilometer and the Essilor Digital CRP. For PD, the test was measured against the Rosenbaum Pocket Vision Screener (RPVS). Reliability was analyzed with intraclass correlation coefficients (ICC) between trials with Cronbach's alpha (CA) and the standard error of measurement for each ICC. Convergent validity was investigated by calculating the bivariate correlation coefficient. RESULTS: Reliability results were strong (CA > 0.7) for all measures. High positive significant correlations were found between the RightEye IPD test and the PL850 Pupilometer (P < 0.001) and Essilor Digital CRP (P < 0.001) and for the RightEye PD test and the RPVS (P < 0.001). CONCLUSIONS: Using infrared eye tracking and the RightEye IPD/PD test stimuli, reliable and accurate measures of IPD and PD were found. Results from normative data showed an adequate comparison for people with normal vision development. TRANSLATIONAL RELEVANCE: Results revealed a central point of fixation may remove variability in examining PD reliably using infrared eye tracking when consistent environmental and experimental procedures are conducted.

A comparison of visual search strategies of elite and non-elite tennis players through cluster analysis.

Considerable research has documented that successful performance in interceptive tasks (such as return of serve in tennis) is based on the performers' capability to capture appropriate anticipatory information prior to the flight path of the approaching object. Athletes of higher skill tend to fixate on different locations in the playing environment prior to initiation of a skill than their lesser skilled counterparts. The purpose of this study was to examine visual search behaviour strategies of elite (world ranked) tennis players and non-ranked competitive tennis players (n = 43) utilising cluster analysis. The results of hierarchical (Ward's method) and nonhierarchical (k means) cluster analyses revealed three different clusters. The clustering method distinguished visual behaviour of high, middle-and low-ranked players. Specifically, high-ranked players demonstrated longer mean fixation duration and lower variation of visual search than middle-and low-ranked players. In conclusion, the results demonstrated that cluster analysis is a useful tool for detecting and analysing the areas of interest for use in experimental analysis of expertise and to distinguish visual search variables among participants'.