14 research outputs found
Subjective Visual Vertical (SVV) Patterns Obtained Using Different Translation Times during Unilateral Centrifugation (UC) Testing
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Distinctive Convergence Eye Movements in an Acquired Neurosensory Dysfunction
In late 2016, diplomats in Havana, Cuba, began presenting with a unique symptom complex after perceiving a strange noise and/or feeling a pressure field in their domicile. This report is a retrospective, quantitative analysis of video-oculography data of pupillary light reflex performance and binocular disparity-driven eye and pupil movements during the acute time period after the reported exposure. The patterns of response in these 19 individuals are markedly different than those seen in a group of individuals with the usual acute mild traumatic brain injury (17 subjects) and from 62 control subjects (21–60 years old) with no injury. Non-linear least squares regression was used to estimate the model parameters from the eye movement and the pupil measurements (
1
). Linear discriminant analysis was then used to identify a classifier for an objective discrimination of the groups with >91% accuracy and no confusion between the acute neurosensory findings among the members of the Havana diplomatic community and the subjects with acute mild traumatic brain injury. This pattern difference in eye and pupil behavior may be a useful screen to help objectively distinguish blunt trauma from Havana-type effects in the future and to guide the affected individuals to appropriate care
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Frequency dependence of coordinated pupil and eye movements for binocular disparity tracking
IntroductionCoordinated alignment of the eyes during gaze fixation and eye movements are an important component of normal visual function. We have previously described the coordinated behavior of convergence eye movements and pupillary responses using a 0.1 Hz binocular disparity-driven sine profile and a step profile. The goal of this publication is to further characterize ocular vergence-pupil size coordination over a wider range of frequencies of ocular disparity stimulation in normal subjects.MethodsBinocular disparity stimulation is generated by presentation of independent targets to each eye on a virtual reality display, while eye movements and pupil size are measured by an embedded video-oculography system. This design allows us to study two complimentary analyses of this motion relationship. First, a macroscale analysis describes the vergence angle of the eyes in response to binocular disparity target movement and pupil area as a function of the observed vergence response. Second, a microscale analysis performs a piecewise linear decomposition of the vergence angle and pupil relationship to permit more nuanced findings.ResultsThese analyses identified three main features of controlled coupling of pupil and convergence eye movements. First, a near response relationship operates with increasing prevalence during convergence (relative to the “baseline” angle); the coupling is higher with increased convergence in this range. Second, the prevalence of “near response”-type coupling decreases monotonically in the diverging direction; the decrease persists after the targets move (converge back) from maximum divergence toward the baseline positions, with a minimum prevalence of near response segments near the baseline target position. Third, an opposite polarity pupil response is infrequent, but tends to be more prevalent when the vergence angles are at maximum convergence or divergence for a sinusoidal binocular disparity task.DiscussionWe suggest that the latter response is an exploratory “range-validation” when binocular disparity is relatively constant. In a broader sense, these findings describe operating characteristics of the near response in normal subjects and form a basis for quantitative assessments of function in conditions such as convergence insufficiency and mild traumatic brain injury
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Statistical Considerations for Subjective Visual Vertical and Subjective Visual Horizontal Assessment in Normal Subjects
Objectives: Judgments of the subjective visual vertical (SVV) and subjective visual horizontal (SVH) while seated upright are commonly included in standard clinical test batteries for vestibular function. We examined SVV and SVH data from retrospective control to assess their statistical distributions and normative values for magnitudes of the preset effect, sex differences, and fixed-head versus head-free device platforms for assessment. Methods: Retrospective clinical SVV and SVH data from 2 test platforms, Neuro-otologic Test Center (NOTC) and the Neurolign Dx 100 (I-Portal Portable Assessment System Nystagmograph) were analyzed statistically (SPSS and MATLAB software) for 408 healthy male and female civilians and military service members, aged 18–50 years. Results: No prominent age-related effects were observed. The preset angle effects for both SVV and SVH, and their deviations from orthogonality, agree in magnitude with previous reports. Differences attributable to interactions with device type and sex are of small magnitude. Analyses confirmed that common clinical measure for SVV and SVH, the average of equal numbers of clockwise and counterclockwise preset trials, was not significantly affected by the test device or sex of the subject. Finally, distributional analyses failed to reject the hypothesis of underlying Gaussian distributions for the clinical metrics. Conclusions: z scores based on these normative findings can be used for objective detection of outliers from normal functional limits in the clinic
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OCULOMOTOR, VESTIBULAR & REACTION TIME OUTCOMES IN INDY 500 DRIVERS COMPARED TO ATHLETES AT START OF SEASON & AFTER MTBI EVENT
Distribution Scores.
<p>Cumulative distribution scores analyzed by sex of subject. Gray squares (female controls) and gray diamond (male controls) show on difference across symptoms clusters whereas the black squares (female mTBI) and black diamonds (male mTBI) vary across the dizziness/cognitive and headache/migraine clusters.</p
Trail Making Test B (TMTB).
<p>Self-administered pattern test going from numbers to corresponding letters in the alphabet as follows: 1→A→2→B→…→12→L→13. The pencil may not leave the paper during the test. Time to complete the tracing is recorded.</p
Portable eye-tracking as a reliable assessment of oculomotor, cognitive and reaction time function: Normative data for 18-45 year old
Eye movements measured by high precision eye-tracking technology represent a sensitive, objective, and non-invasive method to probe functional neural pathways. Oculomotor tests (e.g., saccades and smooth pursuit), tests that involve cognitive processing (e.g., antisaccade and predictive saccade), and reaction time tests have increasingly been showing utility in the diagnosis and monitoring of mild traumatic brain injury (mTBI) in research settings. Currently, the adoption of these tests into clinical practice is hampered by a lack of a normative data set. The goal of this study was to construct a normative database to be used as a reference for comparing patients' results. Oculomotor, cognitive, and reaction time tests were administered to male and female volunteers, aged 18-45, who were free of any neurological, vestibular disorders, or other head injuries. Tests were delivered using either a rotatory chair equipped with video-oculography goggles (VOG) or a portable virtual reality-like VOG goggle device with incorporated infrared eye-tracking technology. Statistical analysis revealed no effects of age on test metrics when participant data were divided into pediatric (i.e.,18-21 years, following FDA criteria) and adult (i.e., 21-45 years) groups. Gender (self-reported) had an effect on auditory reaction time, with males being faster than females. Pooled data were used to construct a normative database using 95% reference intervals (RI) with 90% confidence intervals on the upper and lower limits of the RI. The availability of these RIs readily allows clinicians to identify specific metrics that are deficient, therefore aiding in rapid triage, informing and monitoring treatment and/or rehabilitation protocols, and aiding in the return to duty/activity decision. This database is FDA cleared for use in clinical practice (K192186)