Video-oculography System Research Articles

Automatic Video-Oculography System for Detection of Minimal Hepatic Encephalopathy Using Machine Learning Tools.

This article presents an automatic gaze-tracker system to assist in the detection of minimal hepatic encephalopathy by analyzing eye movements with machine learning tools. To record eye movements, we used video-oculography technology and developed automatic feature-extraction software as well as a machine learning algorithm to assist clinicians in the diagnosis. In order to validate the procedure, we selected a sample (n=47) of cirrhotic patients. Approximately half of them were diagnosed with minimal hepatic encephalopathy (MHE), a common neurological impairment in patients with liver disease. By using the actual gold standard, the Psychometric Hepatic Encephalopathy Score battery, PHES, patients were classified into two groups: cirrhotic patients with MHE and those without MHE. Eye movement tests were carried out on all participants. Using classical statistical concepts, we analyzed the significance of 150 eye movement features, and the most relevant (p-values ≤ 0.05) were selected for training machine learning algorithms. To summarize, while the PHES battery is a time-consuming exploration (between 25-40 min per patient), requiring expert training and not amenable to longitudinal analysis, the automatic video oculography is a simple test that takes between 7 and 10 min per patient and has a sensitivity and a specificity of 93%.

Frequency dependence of coordinated pupil and eye movements for binocular disparity tracking.

Coordinated 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. Binocular 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. These 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. We 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.

Oculomotor fatigability with decrements of saccade and smooth pursuit for diagnosis of myasthenia gravis

Background and objectivesAs the efficacy of current diagnostic methods for myasthenia gravis (MG) remains suboptimal, there is ongoing interest in developing more effective diagnostic models. As oculomotor fatigability is one of the most common and diagnostic symptoms in MG, we aimed to investigate whether quantitative saccadic and smooth-pursuit fatigability analyses with video-oculography (VOG) are useful for diagnosis of MG.MethodsA convenience cohort of 46 MG patients was recruited prospectively, including 35 with ocular and 11 with generalized MG (mean age, 50.9 ± 14.5 years; 17 females); 24 healthy controls (HCs) (mean age, 50.6 ± 16.3 years; 13 females) also were enrolled. Seventy-five repetitive saccades and smooth pursuits were recorded in ranges of 20° (horizontal plane) and 15° (vertical plane) using a three-dimensional VOG system. Based on the oculomotor range of the second saccade and smooth pursuit and the mean ranges of the last five of each, the estimated decrements (%) reflecting oculomotor fatigability were calculated.ResultsThe baseline oculomotor ranges did not show significant difference between the MG and HCs groups. However, following repetitive saccades and pursuits, the oculomotor ranges were decreased substantially during the last five cycles compared to baseline in the MG group. No such decrements were observed in the HC group (p < 0.01, Mann–Whitney U test). Receiver operating characteristic (ROC) analysis revealed that repetitive vertical saccades yielded the best differentiation between the MG and HC groups, with a sensitivity of 78.3% and specificity of 95.8% when using a decrement with an amplitude of 6.4% as the cutoff.ConclusionThis study presents an objective and reproducible method for measuring decrements of oculomotor ranges after repetitive saccadic and pursuit movements. Quantification of oculomotor fatigability using VOG could be a sensitive and specific diagnostic tool for MG and allows easy, cost-effective, accurate, and non-invasive measurements.Classification of evidenceThis study provides class III evidence that VOG-based quantification of saccadic and pursuit fatigability accurately identifies patients with MG.

Ocular-following responses in school-age children.

Ocular following eye movements have provided insights into how the visual system of humans and monkeys processes motion. Recently, it has been shown that they also reliably reveal stereoanomalies, and, thus, might have clinical applications. Their translation from research to clinical setting has however been hindered by their small size, which makes them difficult to record, and by a lack of data about their properties in sizable populations. Notably, they have so far only been recorded in adults. We recorded ocular following responses (OFRs)-defined as the change in eye position in the 80-160 ms time window following the motion onset of a large textured stimulus-in 14 school-age children (6 to 13 years old, 9 males and 5 females), under recording conditions that closely mimic a clinical setting. The OFRs were acquired non-invasively by a custom developed high-resolution video-oculography system, described in this study. With the developed system we were able to non-invasively detect OFRs in all children in short recording sessions. Across subjects, we observed a large variability in the magnitude of the movements (by a factor of 4); OFR magnitude was however not correlated with age. A power analysis indicates that even considerably smaller movements could be detected. We conclude that the ocular following system is well developed by age six, and OFRs can be recorded non-invasively in young children in a clinical setting.

A Highly Integrated Ambient Light Robust Eye-Tracking Sensor for Retinal Projection AR Glasses Based on Laser Feedback Interferometry

Robust and highly integrated eye-tracking is a key technology to improve resolution of near-eye-display technologies for augmented reality (AR) glasses such as focus-free retinal projection as it enables display enhancements like foveated rendering. Furthermore, eye-tracking sensors enables novel ways to interact with user interfaces of AR glasses, improving thus the user experience compared to other wearables. In this work, we present a novel approach to track the user's eye by scanned laser feedback interferometry sensing. The main advantages over modern video-oculography (VOG) systems are the seamless integration of the eye-tracking sensor and the excellent robustness to ambient light with significantly lower power consumption. We further present an algorithm to track the bright pupil signal captured by our sensor with a significantly lower computational effort compared to VOG systems. We evaluate a prototype to prove the high robustness against ambient light and achieve a gaze accuracy of 1.62\,$^\circ$, which is comparable to other state-of-the-art scanned laser eye-tracking sensors. The outstanding robustness and high integrability of the proposed sensor will pave the way for everyday eye-tracking in consumer AR glasses.

The Role of Different Afferent Systems in the Modulation of the Otolith-Ocular Reflex After Long-Term Space Flights.

BackgroundThe vestibular (otolith) function is highly suppressed during space flight (SF) and the study of these changes is very important for the safety of the space crew during SF missions. The vestibular function (particularly, otolith-ocular reflex–OOcR) in clinical and space medicine is studied using different methodologies. However, different methods and methodologies can influence the outcome results.ObjectiveThe current study addresses the question of whether the OOcR results obtained by different methods are different, and what the role is of the different afferent systems in the modulation of the OOcR.MethodsA total of 25 Russian cosmonauts voluntarily took part in our study. They are crewmembers of long duration space missions on the International Space Station (ISS). Cosmonauts were examined in pre- and post-flight “Sensory Adaptation” and “Gaze Spin” experiments, twice before (preflight) and three times after SF (post-flight). We used two different video oculography (VOG) systems for the recording of the OOcR obtained in each experiment.ResultsComparison of the two VOG systems didn’t result into significant and systematic differences in the OOcR measurements. Analysis of the static torsion otolith–ocular reflex (OOR), static torsion otolith–cervical–ocular reflex (OCOR) and static torsion otolith–ocular reflex during eccentric centrifugation (OOREC) shows that the OOREC results in a lower OOcR response compared to the OOR and OCOR (before flight and late post-flight). However, all OOcRs were significantly decreased in all cosmonauts early post-flight.ConclusionAnalysis of the results of ocular counter rolling (OCR) obtained by different methods (OOR, OCOR, and OOREC) showed that different afferent systems (tactile-proprioception, neck-cervical, visual and vestibular afferent input) have an impact on the OOcR.

Identification of Stroke and TIA in Patients With Acute Dizziness, Vertigo or Imbalance in Emergency Departments of Primary Care Hospitals: Early Experiences With a Network-Based Telemedical Approach.

BackgroundAcute dizziness, vertigo, and imbalance are frequent and difficult to interpret symptoms in the emergency department (ED). Primary care hospitals often lack the expertise to identify stroke or TIA as underlying causes. A telemedical approach based on telestroke networks may offer adequate diagnostics and treatment.AimThe aim of this study is to evaluate the accuracy of a novel ED algorithm in differentiating between peripheral and central vestibular causes.MethodsWithin the Telemedical Project for Integrative Stroke Care (TEMPiS), a telemedical application including a videooculography (VOG) system was introduced in 2018 in 19 primary care spoke hospitals. An ED triage algorithm was established for all patients with acute dizziness, vertigo, or imbalance of unknown cause (ADVIUC) as a leading complaint. In three predefined months, all ADVIUC cases were prospectively registered and discharge letters analyzed. Accuracy of the ED triage algorithm in differentiation between central and peripheral vestibular cases was analyzed by comparison of ED diagnoses to final discharge diagnoses. The rate of missed strokes was calculated in relation to all cases with a suitable brain imaging. Acceptance of teleconsultants and physicians in spoke hospitals was assessed by surveys.ResultsA total number of 388 ADVIUC cases were collected, with a median of 12 cases per months and hospital (IQR 8–14.5). The most frequent hospital discharge diagnoses are vestibular neuritis (22%), stroke/TIA (18%), benign paroxysmal positioning vertigo (18%), and dizziness due to internal medicine causes (15%). Detection of a central vestibular cause by the ED triage algorithm has a high sensitivity (98.6%), albeit poor specificity (45.9%). One stroke out of 32 verified by brain scan was missed (3.1%). User satisfaction, helpfulness of the project, improvement of care, personal competence, and satisfaction about handling of the VOG systems were rated consistently positive.DiscussionThe concept shows good acceptance for a telemedical and network-based approach to manage ADVIUC cases in the ED of primary care hospitals. Identification of stroke cases is accurate, while specificity needs further improvement. The concept could be a major step toward a broadly available state of the art diagnostics and therapy for patients with ADVIUC in primary care hospitals.

Novel Hybrid Brain-Computer Interface for Virtual Reality Applications Using Steady-State Visual-Evoked Potential-Based Brain-Computer Interface and Electrooculogram-Based Eye Tracking for Increased Information Transfer Rate.

Brain–computer interfaces (BCIs) based on electroencephalogram (EEG) have recently attracted increasing attention in virtual reality (VR) applications as a promising tool for controlling virtual objects or generating commands in a “hands-free” manner. Video-oculography (VOG) has been frequently used as a tool to improve BCI performance by identifying the gaze location on the screen, however, current VOG devices are generally too expensive to be embedded in practical low-cost VR head-mounted display (HMD) systems. In this study, we proposed a novel calibration-free hybrid BCI system combining steady-state visual-evoked potential (SSVEP)-based BCI and electrooculogram (EOG)-based eye tracking to increase the information transfer rate (ITR) of a nine-target SSVEP-based BCI in VR environment. Experiments were repeated on three different frequency configurations of pattern-reversal checkerboard stimuli arranged in a 3 × 3 matrix. When a user was staring at one of the nine visual stimuli, the column containing the target stimulus was first identified based on the user’s horizontal eye movement direction (left, middle, or right) classified using horizontal EOG recorded from a pair of electrodes that can be readily incorporated with any existing VR-HMD systems. Note that the EOG can be recorded using the same amplifier for recording SSVEP, unlike the VOG system. Then, the target visual stimulus was identified among the three visual stimuli vertically arranged in the selected column using the extension of multivariate synchronization index (EMSI) algorithm, one of the widely used SSVEP detection algorithms. In our experiments with 20 participants wearing a commercial VR-HMD system, it was shown that both the accuracy and ITR of the proposed hybrid BCI were significantly increased compared to those of the traditional SSVEP-based BCI in VR environment.

Feasibility of Telemedical HINTS (Head Impulse-Nystagmus-Test of Skew) Evaluation in Patients With Acute Dizziness or Vertigo in the Emergency Department of Primary Care Hospitals.

BackgroundAcute dizziness, vertigo and imbalance are common symptoms in emergency departments. Stroke needs to be distinguished from vestibular diseases. A battery of three clinical bedside tests (HINTS: Head Impulse Test, Nystagmus, Test of Skew) has been shown to detect stroke as underlying cause with high reliability, but implementation is challenging in primary care hospitals. Aim of this study is to prove the feasibility of a telemedical HINTS examination via a remotely controlled videooculography (VOG) system.MethodsThe existing video system of our telestroke network TEMPiS (Telemedic Project for Integrative Stroke Care) was expanded through a VOG system. This feature enables the remote teleneurologist to assess a telemedical HINTS examination based on inspection of eye movements and quantitative video head impulse test (vHIT) evaluation. ED doctors in 11 spoke hospitals were trained in performing vHIT, nystagmus detection and alternating cover test. Patients with first time acute dizziness, vertigo or imbalance, whether ongoing or resolved, presented to the teleneurologist were included in the analysis, as long as no focal neurological deficit according to the standard teleneurological examination or obvious internal medicine cause was present and a fully trained team was available. Primary outcome was defined as the feasibility of the telemedical HINTS examination.ResultsFrom 01.06.2019 to 31.03.2020, 81 consecutive patients were included. In 72 (88.9%) cases the telemedical HINTS examination was performed. The complete telemedical HINTS examination was feasible in 46 cases (63.9%), nystagmus detection in all cases (100%) and alternating covert test in 70 cases (97.2%). The vHIT was recorded and interpretable in 47 cases (65.3%). Results of the examination with the VOG system yielded clear results in 21 cases (45.7%) with 14 central and 7 peripheral lesions. The main reason for incomplete examination was the insufficient generation of head impulses.ConclusionIn our analysis the telemedical HINTS examination within a telestroke network was feasible in two thirds of the patients. This offers the opportunity to improve specific diagnostics and therapy for patients with acute dizziness and vertigo even in primary care hospitals. Improved training for spoke hospital staff is needed to further increase the feasibility of vHIT.

Upbeat Nystagmus with an Unusual Velocity-Decreasing and Increasing Waveform: a Sign of Gaze-Holding Dysfunction in the Paramedian Tracts in the Medulla?

We report a patient with spontaneous upbeat nystagmus (UBN) due to an ischemic lesion involving the paramedian tract (PMT) in the medulla. Eye movement recordings, using an infrared video-oculography (VOG) system, showed that the slow phase of the nystagmus was initially velocity-decreasing but gradually became velocity-increasing. Simulation of the nystagmus with a mathematical model supports a role for the PMT in relaying premotor signals for vertical gaze holding to the cerebellum. Our model shows that the disruption in cerebellar input from PMT can lead to the velocity-increasing waveform of the nystagmus, whereas the velocity-decreasing waveform could be related to a mismatch between the innervational commands to the ocular muscles (the pulse and step) needed to hold gaze steady.

A novel 3D video oculography system for measuring cross-axis vestibulo-ocular reflex

We present a video oculography (VOG) system with 6-degree-of-freedom (6-DOF) mobility for real-time measurements of the binocular 3D eye position of a small animal. A hybrid hexapod that allowed for multi-axis complex motions with the resolution of the microscopic level was used to control the motion of the animal. The instantaneous eyeball movement of the animal was determined based on two approaches: (1) tracking of marker arrays affixed to the cornea; and (2) tracking the pupil outline. The tracking of the eyeball movement and the motion control of the hexapod were implemented with the LabVIEW virtual instruments. Compared with our previous measurements using a servo-motor-based single-axis VOG system, positional error reduced from more than 4% to less than 0.7%. Validation showed that the tracking errors in three rotational axes are less than 2% for the magnitude and less than 5° for the direction angle. The present VOG system is an effective tool for cross-axis 3D vestibulo-ocular reflex study on small animals.

Automated alternate cover test for 'HINTS' assessment: a validation study.

ObjectiveThe alternate cover test (ACT) in patients with acute vestibular syndrome is part of the ‘HINTS’ battery test. Although quantitative, the ACT is highly dependent on the examiner’s experience and could theoretically vary greatly between examiners. In this study, we sought to validate an automated video-oculography (VOG) system based on eye tracking and dedicated glasses.MethodsWe artificially induced a vertical strabismus to simulate a skew deviation on ten healthy subjects, aged from 26 to 66, using different press-on Fresnel prisms on one eye while recording eye position with VOG of the contralateral eye. We then compared the system’s performance to that of a blinded trained orthoptist using conventional, semi-quantitative method of skew measurement known as the alternate prism cover test (APCT) as a gold standard.ResultsWe found a significant correlation between the reference APCT and the Skew VOG (Pearson’s R2 = 0.606, p < 0.05). There was a good agreement between the two tests (intraclass correlation coefficient 0.852, 95 CI 0.728–0.917, p < 0.001). The overall accuracy of the VOG was estimated at 80.53% with an error rate of 19.46%. There was no significant difference in VOG skew estimations compared with the gold standard except for very small skews.ConclusionsVOG offers an objective and quantitative skew measurement and proved to be accurate in measuring vertical eye misalignment compared to the ACT with prisms. Precision was moderate, which mandates a sufficient number of tests per subject.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00405-021-06998-w.

Comparative analysis of spontaneous blinking and the corneal reflex.

Ocular surface health, the cognitive status, psychological health or human neurological disorders, among others, can be assessed by studying eye blinking, which can be differentiated in spontaneous, reflex and voluntary. Its diagnostic potential has provided a great number of works that evaluate their characteristics and variations depending on the subject's condition (sex, tiredness, health, …). The objective of this study was to analyse the differences in blinking kinematics of spontaneous and reflex blinks, distinguishing between direct and consensual reflexes, using a self-developed, non-invasive and image processing-based method. A video-oculography system is proposed using an air jet driven by a syringe to induce reflex and a high-speed camera to record the blinking of both eyes. The light intensity diffused by the eye changes during blinking and peaks when the eyelid closes. Sixty-second sequences were recorded of 25 subjects blinking. Intensity curves were off-line fitted to an exponentially modified Gaussian (EMG) function, whose σ, μ and τ parameters were analysed. A two-way analysis of variance (ANOVA) of these parameters was conducted to test the influence of the subject, the eye and blink type. In the closing phase, direct and consensual corneal reflexes are faster than spontaneous blinking, but there was no significant difference between them, nor between right and left eyes. In the opening phase, the direct corneal reflex was the slowest and significant differences appeared between right and left eyes.

Eye Blink Detection System for Paralyzed Patients

Paralysis of an human being is caused due to the degeneration of motor neurons which weakens the muscle, so that it does not allow patient to move, speak, breathe , and loss in the voluntary actions. It is an incurable disease. To understand the feelings of a paralyzed patients Brain wave technique and Electro-oculography techniques were used. These techniques are afflictive, discomfortable and leads to unconsciousness of the paralyzed patient. The real time video oculography system fills the communication gap between the patient and the world. Video Oculography (VOG) is video-based method of measuring the vertical, torsional and horizontal position components of both the eye blinks with the help of small cameras placed in the head-mounted mask .This paper presents different visual technologies, such as eye blink detection, eye center localization and conversion of the eye blink to speech. The video oculography could achieve accuracy of 0.968.

Horizontal Vestibulo-Ocular Reflex Gain Measures During Convergence Using a Monocular Video Technique.

Vestibulo-ocular reflex (VOR) response measures during convergence, which are clinically important to measure peripheral vestibular organ function during rotational and translational rapid head movements, can be implemented using existing clinically available monocular video-oculography (VOG) systems. We have developed and validated a monocular VOG technique that allows for accurate measurement of the convergence angle immediately before a rapid translational or rotational head movement. We recorded binocular eye movements while subjects performed active or passive horizontal head impulses while viewing near and far targets. We calculated the convergence angles and VOR gains using monocular and binocular methods and compared them with a geometric model. The monocular VOG technique resulted in convergence angle and VOR gain (eye velocity/head velocity) calculations that differed by ∼10% compared with values calculated using the binocular data. The monocular VOG technique can be clinically implemented using any unmodified, commercially available, monocular VOG system, provided its camera can be positioned to track either eye. Many vestibular clinics already have access to such systems. This method makes possible reliable measurement of the near-viewing horizontal angular VOR during the head impulse test, the translational VOR during the head heave test in patients, and the clinical measurement of convergence insufficiency.

Combined exposure to carbon disulfide and low-frequency noise reversibly affects vestibular function

Chronic occupational exposure to carbon disulfide (CS2) has debilitating motor and sensory effects in humans, which can increase the risk of falls. Although no mention of vestibulotoxic effects is contained in the literature, epidemiological and experimental data suggest that CS2 could cause low-frequency hearing loss when associated with noise exposure. Low-frequency noise might also perturb the peripheral balance receptor through an as-yet unclear mechanism. Here, we studied how exposure to a low-frequency noise combined with 250-ppm CS2 affected balance in rats. Vestibular function was tested based on post-rotary nystagmus recorded by a video-oculography system. These measurements were completed by behavioral tests and analysis of the cerebellum to measure expression levels for gene expression associated with neurotoxicity. Assays were performed prior to and following a 4-week exposure, and again after a 4-week recovery period. Functional measurements were completed by histological analyses of the peripheral organs.Nystagmus was unaltered by exposure to noise alone, while CS2 alone caused a moderate 19% decrease of the saccade number. In contrast, coexposure to 250-ppm CS2 and low-frequency noise decreased both saccade number and duration by 33% and 34%, respectively. After four weeks, recovery was only partial but measures were not significantly different from pre-exposure values. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis of cerebellar tissue revealed a slight but significant modification in expression levels for two genes linked to neurotoxicity in CS2-exposed animals. However, neither histopathological changes to the peripheral receptor nor behavioral differences were observed. Based on all these results, we propose that the effects of CS2 were due to reversible neurochemical disturbance of the efferent pathways managing post-rotatory nystagmus. Because the nervous structures involving the vestibular function appear particularly sensitive to CS2, post-rotary nystagmus could be used as an early, non-invasive measurement to diagnose CS2 intoxication as part of an occupational conservation program.

Eye Movements Evoked by Pulsed Infrared Radiation of the Rat Vestibular System.

Light at infrared wavelengths has been demonstrated to modulate the pattern of neural signals transmitted from the angular motion sensing semicircular canals of the vestibular system to the brain. In the present study, we have characterized physiological eye movements evoked by focused, pulsed infrared radiation (IR) stimuli directed at an individual semicircular canal in a mammalian model. Pulsed IR (1863nm) trains were directed at the posterior semicircular canal in a rat using 200-400µm optical fibers. Evoked bilateral eye movements were measured using a custom-modified video-oculography system. The activation of vestibulo-ocular motor pathways by frequency modulated pulsed IR directed at single posterior semicircular canals evoked significant, characteristic bilateral eye movements. In this case, the resulting eye movements were disconjugate with ipsilateral eye moving upwards with a rotation towards the stimulated ear and the contralateral eye moving downwards. The eye movements were stable through several hours of repeated stimulation and could be maintained with 30 + minutes of continuous, frequency-modulated IR stimulation. Following the measurements, the distance of the fiber from target structures and orientation of the beam relative to vestibular structures were determined using micro-computed tomography. Results highlight the spatial selectivity of optical stimulation. Our results demonstrate a novel strategy for direct optical stimulation of the vestibular pathway in rodents and lays the groundwork for future applications of optical neural stimulation in inner ear research and therapeutic applications.

A head-mounted goggle-type video-oculography system for vestibular function testing

Disorders of the vestibular system possibly decrease vision, causing abnormal nystagmus and dizziness. To diagnose abnormal nystagmus, various studies have been reported including the use of rotating chair tests and videonystagmography. However, these tests are unsuitable for home use due to their high costs. Thus, a low-cost video-oculography system is necessary to obtain clinical features at home. In this paper, we present a goggle-type low-cost video-oculography system using an infrared camera and Raspberry Pi board for tracking the pupils and evaluating a vestibular system. Horizontal eye movement is derived from video data obtained from an infrared camera and infrared light-emitting diodes, and the velocity of head rotation is obtained from a gyroscope sensor. Each pupil was extracted using a morphology operation and a contour detection method. Rotatory chair tests were conducted with our developed device. To evaluate our system, gain, symmetry, and phase were measured and compared System 2000.

Bilateral vestibulopathy

The leading symptoms of bilateral vestibulopathy (BVP) are postural imbalance and unsteadiness of gait, deficits of spatial memory and navigation. The etiology of BVP remains unclear in more than 50% of patients: in these cases neurodegeneration is assumed. Frequent known causes are ototoxicity mainly due to gentamicin, bilateral Menière's disease, autoimmune diseases, meningitis and bilateral vestibular schwannoma, as well as an association with cerebellar degeneration. The diagnosis of BVP is based on a bilaterally reduced or absent function of the vestibulo-ocular reflex (VOR). Head impulse test (HIT), video-oculography system (vHIT), crvical/ocular vestibular-evoked myogenic potentials (c/oVEMP) and dynamic visual acuity is an additional test supporting the diagnosis. There are four different subtypes of BVP depending on the affected anatomic structure and frequency range of the VOR deficit: impaired canal function in the low-and/or high-frequency VOR range only and/or otolith function only; the latter is very rare. There are four treatment options: first, detailed patient counseling to explain the cause, etiology, and consequences, as well as the course of the disease; second, daily vestibular exercises and balance training; third, if possible, treatment of the underlying cause, as in bilateral Menière's disease, meningitis, or autoimmune diseases; fourth, if possible, prevention, i.e., being very restrictive with the use of ototoxic substances, such as aminoglycosides.

A low-cost video-oculography system for vestibular function testing.

In order to remain in focus during head movements, vestibular-ocular reflex causes eyes to move in the opposite direction to head movement. Disorders of vestibular system decrease vision, causing abnormal nystagmus and dizziness. To diagnose abnormal nystagmus, various studies have been reported including the use of rotating chair tests and videonystagmography. However, these tests are unsuitable for home use due to their high costs. Thus, a low-cost video-oculography system is necessary to obtain clinical features at home. In this paper, we present a low-cost video-oculography system using an infrared camera and Raspberry Pi board for tracking the pupils and evaluating a vestibular system. Horizontal eye movement is derived from video data obtained from an infrared camera and infrared light-emitting diodes, and the velocity of head rotation is obtained from a gyroscope sensor. Each pupil was extracted using a morphology operation and a contour detection method. Rotatory chair tests were conducted with our developed device. To evaluate our system, gain, asymmetry, and phase were measured and compared with System 2000. The average IQR errors of gain, phase and asymmetry were 0.81, 2.74 and 17.35, respectively. We showed that our system is able to measure clinical features.