Primate eye tracking with carbon-nanotube-paper-composite based capacitive sensors and machine learning algorithms.

BACKGROUND: Accurate real-time eye tracking is crucial in oculomotor system research. While the scleral search coil system is the gold standard, its implantation procedure and bulkiness pose challenges. Camera-based systems are affected by ambient lighting and require high computational and electric power. NEW METHOD: This study presents a novel eye tracker using proximity capacitive sensors made of carbon-nanotube-paper-composite (CPC). These sensors detect femtofarad-level capacitance changes caused by primate corneal movement during horizontal and vertical eye rotations. Data processing and machine learning algorithms are evaluated to enhance the accuracy of gaze angle prediction. RESULTS: The system performance is benchmarked against the scleral coil during smooth pursuits, saccades tracking, and fixations. The eye tracker demonstrates up to 0.97 correlation with the coil in eye tracking and is capable of estimating gaze angle with a median absolute error as low as 0.30°. COMPARISON: The capacitive eye tracker demonstrates good consistency and accuracy in comparison to the gold-standard scleral search coil method. CONCLUSIONS: This lightweight, non-invasive capacitive eye tracker offers potential as an alternative to traditional coil and camera-based systems in oculomotor research and vision science.

Designing Novel Physiologic Monitor Displays for Combat Medics.

INTRODUCTION: Combat medics who are responsible for the care of injured warfighters face challenges from their reliance on medical alarms that exceed the noise levels recommended by the WHO. This is because the elevated noise levels in military facilities, particularly from vehicular units and weaponry, compromise the combat medics' effectiveness and attentiveness to medical alarms. We previously designed a graphical ("configural") display to communicate patients' vital signs and found that when the configural display and traditional numerical display were concurrently presented to participants, it produced the fastest identification of patient vital signs and triggered the fewest number of alarms. This study used eye tracking to assess how participants direct visual attention to and engage with concurrently presented numerical and configural vital sign displays. MATERIALS AND METHODS: We recruited 30 undergraduate students with normal hearing and vision for this study. Subjects were tasked with monitoring a simulated patient's vital signals using simultaneously presented numerical and configural vital sign displays. Concurrently, they performed an N-back task to simulate the multitasking required in a military environment. We manipulated the eccentricity and display position of the numerical and configural displays through 4 orientations, with each orientation being used in a monitoring block lasting 12 minutes. Continuous eye tracking was utilized to collect physiological data about participant display preference. RESULTS: We used eye tracking to analyze several metrics: Total display viewing time, total viewing time percentage, number of dwells (groups of eye fixations), mean fixations per dwell, and fixation patterns during an emergency event. Participants spent more time looking at the configural display than the numerical display during nominal monitoring and emergency events. During emergencies, the percentage of time individuals spent looking at the configural display increased from 30 to 50%, while there was no corresponding increase in the participants' looking at the numerical display. When there were 2 concurrent emergency events instead of 1, total viewing time did not increase, suggesting that participants did not need to change their viewing strategy when the emergency situation complexity increased. Also, during emergencies, participants directed nearly half of their fixations to the configural display during the first 2 seconds of an emergency, while only directing fewer than 5% of fixations to the numerical display during that same period. The average response time for an emergency event was around 2 seconds, which suggests that participants obtained relevant information from the configural display in this time period. CONCLUSIONS: We found that when a patient monitor contains both a configural display and a numerical display, participants look at the configural display. Furthermore, during time-sensitive situations, participants utilize the configural display to provide important information. We suggest this because the configural display integrates the relevant vital signs into one display. These findings provide justification for pursuing integrated vital sign displays to efficiently communicate patient conditions in complex environments. On the battlefield, swift decision-making is essential, as combat medics must minimize the time required to assess and act in critical situations.

Comparative Performance of Three Eye-Tracking Devices in Detection of Mild Traumatic Brain Injury in Acute Versus Chronic Subject Populations.

INTRODUCTION: Presently, traumatic brain injury (TBI) triage in field settings relies on symptom-based screening tools such as the updated Military Acute Concussion Evaluation. Objective eye-tracking may provide an alternative means of neurotrauma screening due to sensitivity to neurotrauma brain-health changes. Previously, the US Army Medical Research and Development Command Non-Invasive NeuroAssessment Devices (NINAD) Integrated Product Team identified 3 commercially available eye-tracking devices (SyncThink EYE-SYNC, Oculogica EyeBOX, NeuroKinetics IPAS) as meeting criteria toward being operationally effective in the detection of TBI in service members. We compared these devices to assess their relative performance in the classification of mild traumatic brain injury (mTBI) subjects versus normal healthy controls. MATERIALS AND METHODS: Participants 18 to 45 years of age were assigned to Acute mTBI, Chronic mTBI, or Control group per study criteria. Each completed a TBI assessment protocol with all 3 devices counterbalanced across participants. Acute mTBI participants were tested within 72 hours following injury whereas time since last injury for the Chronic mTBI group ranged from months to years. Discriminant analysis was undertaken to determine device classification performance in separating TBI subjects from controls. Area Under the Curves (AUCs) were calculated and used to compare the accuracy of device performance. Device-related factors including data quality, the need to repeat tests, and technical issues experienced were aggregated for reporting. RESULTS: A total of 63 participants were recruited as Acute mTBI subjects, 34 as Chronic mTBI subjects, and 119 participants without history of TBI as controls. To maximize outcomes, poorer quality data were excluded from analysis using specific criteria where possible. Final analysis utilized 49 (43 male/6 female, mean [x̅] age = 24.3 years, SD [s] = 5.1) Acute mTBI subjects, and 34 (33 male/1 female, x̅ age = 38.8 years, s = 3.9) Chronic mTBI subjects were age- and gender-matched as closely as possible with Control subjects. AUCs obtained with 80% of total dataset ranged from 0.690 to 0.950 for the Acute Group and from 0.753 to 0.811 for the Chronic mTBI group. Validation with the remaining 20% of dataset produced AUCs ranging from 0.600 to 0.750 for Acute mTBI group and 0.490 to 0.571 for the Chronic mTBI group. CONCLUSIONS: Potential eye-tracking detection of mTBI, per training model outcomes, ranged from acceptable to excellent for the Acute mTBI group; however, it was less consistent for the Chronic mTBI group. The self-imposed targeted performance (AUC of 0.850) appears achievable, but further device improvements and research are necessary. Discriminant analysis models differed for the Acute versus Chronic mTBI groups, suggesting performance differences in eye-tracking. Although eye-tracking demonstrated sensitivity in the Chronic group, a more rigorous and/or longitudinal study design is required to evaluate this observation. mTBI injuries were not controlled for this study, potentially reducing eye-tracking assessment sensitivity. Overall, these findings indicate that while eye-tracking remains a viable means of mTBI screening, device-specific variability in data quality, length of testing, and ease of use must be addressed to achieve NINAD objectives and DoD implementation.

The real-time status of strong and weak islands.

In two eye-tracking reading experiments, we used a variant of the filled gap technique to investigate how strong and weak islands are processed on a moment-to-moment basis during comprehension. Experiment 1 provided a conceptual replication of previous studies showing that real time processing is sensitive to strong islands. In the absence of an island, readers experienced processing difficulty when a pronoun appeared in a position of a predicted gap, but this difficulty was absent when the pronoun appeared inside a strong island. Experiment 2 showed an analogous effect for weak islands: a processing cost was seen for a pronoun in the position of a predicted gap in a that-complement clause, but this cost was absent in a matched whether clause, which constitutes a weak island configuration. Overall, our results are compatible with the claim that active dependency formation is suspended, or reduced, in both weak and strong island structures.

Estudo exploratório sobre análise multimodal da atenção compartilhada / Exploratory study on the multimodal analysis of the joint attention

RESUMO O objetivo deste estudo foi produzir análise multimodal exploratória sobre a atenção compartilhada. Utilizou-se a ferramenta ELAN (EUDICO Language Annotator), software com recursos para sincronização temporal e especiais para modalidades verbal e não verbal, que facilitam a visualização e anotação de contextos interacionais. Foram analisados e transcritos trechos de dez minutos de sessão de avaliação fonoaudiológica de uma criança em investigação para transtorno do espectro do autismo (TEA) e outra, com desenvolvimento típico, pareadas por faixa etária e gênero. Foram investigadas e quantificadas as ocorrências espontâneas de direcionamento do olhar das crianças para: os olhos do interlocutor; os brinquedos e/ou brincadeiras; os olhos do interlocutor - brinquedos (atenção compartilhada). As ocorrências de direcionamento do olhar diferiram entre as crianças de forma quantitativa e qualitativa. A criança com suspeita de TEA não produziu episódio de atenção compartilhada, nem direcionou seu olhar para o interlocutor. Foram 56 ocorrências de direcionamentos de olhar apenas para os brinquedos. A criança em desenvolvimento típico produziu 18 ocorrências de atenção compartilhada, sendo que, em todas as vezes que direcionou o olhar para os olhos do interlocutor, o fez para compartilhar o brinquedo ou brincadeira. Observou-se, ainda, 37 ocorrências de direcionamento do olhar para o brinquedo. A partir da análise exploratória produzida pela ferramenta ELAN, foi possível observar que houve diferença em número de ocorrência e trajetória do olhar entre as duas crianças e verificar que a atenção compartilhada esteve ausente na criança com risco para TEA.

ABSTRACT The aim of this study was to produce exploratory multimodal analysis on joint attention. We used the ELAN tool: software with resources for temporal and special synchronization for verbal and non-verbal modalities that facilitate the visualization and annotation of interactional contexts. Excerpts of ten minutes of speech and language pathology evaluation of the child with suspected ASD and of another child with typical development matched by age group and gender, were analyzed and transcribed. Spontaneous occurrences of the child's gaze were investigated: a) Towards the interlocutor's eyes. b) Towards toys or play. c) Towards the interlocutor's eyes and toys (Joint Attention). The occurrences of look direction differed between children in a quantitative and qualitative way. The child with suspected ASD did not produce an episode of joint attention, nor did he direct his gaze to the interlocutor. There were 56 occurrences of gazing towards the toys. The typical child produced 18 occurrences of joint attention, and whenever he directed his eyes to the interlocutor's eyes, he did so with the intention of sharing the toy or play. We also observed 37 occurrences of gazing towards the toy or play. From the exploratory analysis produced by ELAN tool, it was possible to observe that there were differences in the number of occurrences and look direction between the evaluated children and to verify that the joint attention was absent in the child with ASD risk.

Smile Arc Esthetics in Middle-Aged Man from the Layperson's Perspective Via Eye-Tracking

Abstract Objective: To evaluate the perceptions of smile esthetics associated with variations in the vertical plane of the maxillary incisors in the smile arc using eye-tracking software. Material and Methods: An image of a 59-year-old Caucasian male model was adapted and edited to make three changes in the vertical plane, simulating a convex, straight, and reverse smile arc. Four areas of interest were inserted at the right and left eyes, nose, and mouth. Forty laypeople raters between 18 and 45 years of age participated of the study. Eye-tribe hardware and Ogama software were used to perform eye-tracking. Attractiveness and age-perception questions were also incorporated into the study. ANOVA test and Pearson's correlation coefficient, at p < 0.05. Results: The most observed AOI in images with convex, straight, and reverse smiles, as assessed using heatmaps and point maps, was the mouth, followed by the right eye. A significant difference for the eye (p=0.02) was found when comparing convex and reverse smiles, whereas a significant difference for the mouth was observed between the straight and reverse smiles (p=0.03). Conclusion: Convex and straight smile arcs were associated with equal levels of attractiveness; the reverse smile was less attractive. No significant difference was noticed regarding age perception and the smile arcs. However, the reverse smile recorded a more complete fixation time.

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).

Fast and nonuniform dynamics of perisaccadic vision in the central fovea.

Humans use rapid eye movements (saccades) to inspect stimuli with the foveola, the region of the retina where receptors are most densely packed. It is well established that visual sensitivity is generally attenuated during these movements, a phenomenon known as saccadic suppression. This effect is commonly studied with large, often peripheral, stimuli presented during instructed saccades. However, little is known about how saccades modulate the foveola and how the resulting dynamics unfold during natural visual exploration. Here we measured the foveal dynamics of saccadic suppression in a naturalistic high-acuity task, a task designed after primates' social grooming, which-like most explorations of fine patterns-primarily elicits minute saccades (microsaccades). Leveraging on recent advances in gaze-contingent display control, we were able to systematically map the perisaccadic time course of sensitivity across the foveola. We show that contrast sensitivity is not uniform across this region and that both the extent and dynamics of saccadic suppression vary within the foveola. Suppression is stronger and faster in the most central portion, where sensitivity is generally higher and selectively rebounds at the onset of a new fixation. These results shed light on the modulations experienced by foveal vision during the saccade-fixation cycle and explain some of the benefits of microsaccades.

GazeBase, a large-scale, multi-stimulus, longitudinal eye movement dataset.

This manuscript presents GazeBase, a large-scale longitudinal dataset containing 12,334 monocular eye-movement recordings captured from 322 college-aged participants. Participants completed a battery of seven tasks in two contiguous sessions during each round of recording, including a - (1) fixation task, (2) horizontal saccade task, (3) random oblique saccade task, (4) reading task, (5/6) free viewing of cinematic video task, and (7) gaze-driven gaming task. Nine rounds of recording were conducted over a 37 month period, with participants in each subsequent round recruited exclusively from prior rounds. All data was collected using an EyeLink 1000 eye tracker at a 1,000 Hz sampling rate, with a calibration and validation protocol performed before each task to ensure data quality. Due to its large number of participants and longitudinal nature, GazeBase is well suited for exploring research hypotheses in eye movement biometrics, along with other applications applying machine learning to eye movement signal analysis. Classification labels produced by the instrument's real-time parser are provided for a subset of GazeBase, along with pupil area.

Attentional processes during emotional face perception in social anxiety disorder: A systematic review and meta-analysis of eye-tracking findings.

Background In recent years, a growing body of eye-tracking research has investigated gaze behavior in individuals with social anxiety during the visual perception of emotional stimuli. The aim of this article was to review and synthesize studies examining attention orientation in patients with clinical social anxiety by means of eye-tracking methodology. Methods Through a systematic search, 30 articles were identified, including 11 studies in which single emotional faces were used as stimuli and seven eligible studies in which threatening faces were paired with neutral stimuli. Meta-analyses were conducted to compare prolonged eye-contact behavior and early attentional biases to threats in individuals with social anxiety disorder (SAD) and healthy controls. Results Moderate group differences were revealed for single face viewing studies, with SAD patients showing significantly reduced eye contact with negative (Hedges' g = -0.67) and positive emotional faces (g = -0.49) compared to that of healthy participants. Type of task and duration of stimulus presentation were (marginally) significant moderators of between-study variance in effect size. Small but significant group differences were found for early attentional biases toward angry faces versus neutral stimuli (g = 0.21) but not toward happy faces versus neutral stimuli (g = 0.05). Preliminary evidence for a hyperscanning strategy in SAD patients relative to healthy controls emerged (g = 0.42). Limitations The number of included studies with face pairings was low, and two studies were excluded due to unavailable data. Conclusions Our results suggest that eye contact avoidance with emotional faces is a prominent feature in SAD patients. Patients might benefit from guidance to learn to make adequate eye contact during therapeutic interventions, such as exposure therapy. SAD patients demonstrated slightly heightened attention allocation toward angry faces relative to that of healthy participants during early processing stages. Threat biases can be potential targets for attention modification training as an adjuvant to other treatments. Future research on early attentional processes may benefit from improved arrangements of paired stimuli to increase the psychometric properties of initial attention indices.

Hands-free Adjustment of the Microscope in Microneurosurgery.

BACKGROUND: In microneurosurgery, the operating microscope plays a vital role. The classical neurosurgical operation is bimanual, that is, the microsurgical instruments are operated with both hands. Often, operations have to be carried out in narrow corridors at the depth of several centimeters. With current technology, the operator must manually adjust the field of view during surgery-which poses a disruption in the operating flow. Until now, technical adjuncts existed in the form of a mouthpiece to move the stereo camera unit or voice commands and foot pedals to control other interaction tasks like optical configuration. However, these have not been widely adopted due to usability issues. This study tests 2 novel hands-free interaction concepts based on head positioning and gaze tracking as an attempt to reduce the disruption during microneurosurgery and increase the efficiency of the user. METHODS: Technical equipment included the Pentero 900 microscope (Carl Zeiss Microscopy GmbH, Jena, Germany), HTC Vive Pro (HTC, Taoyuan District (HQ), Taiwan), and an inbuilt 3D-printed target probe. Eleven neurosurgeons including 7 residents and 4 consultants participated in the study. The tasks created for this study were with the intention to mimic real microneurosurgical tasks to maintain applicative accuracy while testing the interaction concepts. The tasks involved visualization system adjustment to the specific target and touching the target. The first trial was conducted in a virtual reality setting applying the novel hands-free interaction concepts, and the second trial was conducted performing the same tasks on a 3D-printed target probe using manual field of view adjustment. The participants completed both trials with the same predetermined tasks, in order to validate the feasibility of the novel technology. The data collected for this study were obtained with the help of review protocols, detailed post-trial interviews, video and audio recordings, along with time measurements while performing the tasks. RESULTS: The user study conducted at the Charité Hospital in Berlin found that the gaze-tracking and head-positioning- based microscope adjustment were 18% and 29% faster, respectively, than the classical bimanual adjustment of the microscope. Focused user interviews showed the users' proclivity for the new interaction concepts, as they offered minimal disruption between the simultaneous target selection and camera position adjustment. CONCLUSIONS: The hands-free interaction concepts presented in this study demonstrated a more efficient execution of the microneurosurgical tasks than the classical manual microscope and were assessed to be more preferable by both residents and consultant neurosurgeons.

Assessing visual search performance using a novel dynamic naturalistic scene.

Daily activities require the constant searching and tracking of visual targets in dynamic and complex scenes. Classic work assessing visual search performance has been dominated by the use of simple geometric shapes, patterns, and static backgrounds. Recently, there has been a shift toward investigating visual search in more naturalistic dynamic scenes using virtual reality (VR)-based paradigms. In this direction, we have developed a first-person perspective VR environment combined with eye tracking for the capture of a variety of objective measures. Participants were instructed to search for a preselected human target walking in a crowded hallway setting. Performance was quantified based on saccade and smooth pursuit ocular motor behavior. To assess the effect of task difficulty, we manipulated factors of the visual scene, including crowd density (i.e., number of surrounding distractors) and the presence of environmental clutter. In general, results showed a pattern of worsening performance with increasing crowd density. In contrast, the presence of visual clutter had no effect. These results demonstrate how visual search performance can be investigated using VR-based naturalistic dynamic scenes and with high behavioral relevance. This engaging platform may also have utility in assessing visual search in a variety of clinical populations of interest.

Portable device for presbyopia correction with optoelectronic lenses driven by pupil response.

A novel portable device has been developed and built to dynamically, and automatically, correct presbyopia by means of a couple of opto-electronics lenses driven by pupil tracking. The system is completely portable providing with a high range of defocus correction up to 10 D. The glasses are controlled and powered by a smartphone. To achieve a truly real-time response, image processing algorithms have been implemented in OpenCL and ran on the GPU of the smartphone. To validate the system, different visual experiments were carried out in presbyopic subjects. Visual acuity was maintained nearly constant for a range of distances from 5 m to 20 cm.

Spintronic Sensors Based on Magnetic Tunnel Junctions for Wireless Eye Movement Gesture Control.

The tracking of eye gesture movements using wearable technologies can undoubtedly improve quality of life for people with mobility and physical impairments by using spintronic sensors based on the tunnel magnetoresistance (TMR) effect in a human-machine interface. Our design involves integrating three TMR sensors on an eyeglass frame for detecting relative movement between the sensor and tiny magnets embedded in an in-house fabricated contact lens. Using TMR sensors with the sensitivity of 11 mV/V/Oe and ten <1 mm3 embedded magnets within a lens, an eye gesture system was implemented with a sampling frequency of up to 28 Hz. Three discrete eye movements were successfully classified when a participant looked up, right or left using a threshold-based classifier. Moreover, our proof-of-concept real-time interaction system was tested on 13 participants, who played a simplified Tetris game using their eye movements. Our results show that all participants were successful in completing the game with an average accuracy of 90.8%.

3-Dimensional magnetic resonance imaging of the freely moving human eye.

Eye motion is a major confound for magnetic resonance imaging (MRI) in neuroscience or ophthalmology. Currently, solutions toward eye stabilisation include participants fixating or administration of paralytics/anaesthetics. We developed a novel MRI protocol for acquiring 3-dimensional images while the eye freely moves. Eye motion serves as the basis for image reconstruction, rather than an impediment. We fully reconstruct videos of the moving eye and head. We quantitatively validate data quality with millimetre resolution in two ways for individual participants. First, eye position based on reconstructed images correlated with simultaneous eye-tracking. Second, the reconstructed images preserve anatomical properties; the eye's axial length measured from MRI images matched that obtained with ocular biometry. The technique operates on a standard clinical setup, without necessitating specialized hardware, facilitating wide deployment. In clinical practice, we anticipate that this may help reduce burdens on both patients and infrastructure, by integrating multiple varieties of assessments into a single comprehensive session. More generally, our protocol is a harbinger for removing the necessity of fixation, thereby opening new opportunities for ethologically-valid, naturalistic paradigms, the inclusion of populations typically unable to stably fixate, and increased translational research such as in awake animals whose eye movements constitute an accessible behavioural readout.

When I Look into Your Eyes: A Survey on Computer Vision Contributions for Human Gaze Estimation and Tracking.

The automatic detection of eye positions, their temporal consistency, and their mapping into a line of sight in the real world (to find where a person is looking at) is reported in the scientific literature as gaze tracking. This has become a very hot topic in the field of computer vision during the last decades, with a surprising and continuously growing number of application fields. A very long journey has been made from the first pioneering works, and this continuous search for more accurate solutions process has been further boosted in the last decade when deep neural networks have revolutionized the whole machine learning area, and gaze tracking as well. In this arena, it is being increasingly useful to find guidance through survey/review articles collecting most relevant works and putting clear pros and cons of existing techniques, also by introducing a precise taxonomy. This kind of manuscripts allows researchers and technicians to choose the better way to move towards their application or scientific goals. In the literature, there exist holistic and specifically technological survey documents (even if not updated), but, unfortunately, there is not an overview discussing how the great advancements in computer vision have impacted gaze tracking. Thus, this work represents an attempt to fill this gap, also introducing a wider point of view that brings to a new taxonomy (extending the consolidated ones) by considering gaze tracking as a more exhaustive task that aims at estimating gaze target from different perspectives: from the eye of the beholder (first-person view), from an external camera framing the beholder's, from a third-person view looking at the scene where the beholder is placed in, and from an external view independent from the beholder.

Wearing a head-mounted eye tracker may reduce body sway.

This study investigated the effects of wearing a head-mounted eye tracker on upright balance during different visual tasks. Twenty five young adults stood upright on a force plate while performing the visual tasks of fixation, horizontal saccades, and eyes closed, during eighteen trials wearing or not a head-mounted eye tracker. While wearing the eye tracker, participants showed a reduction in mean sway amplitude and velocity of the CoP in the AP and ML directions and more regular CoP fluctuations, in the ML axis in all conditions. Higher mean sway amplitude and velocity of CoP were observed during eyes closed than fixation and saccades. Moreover, horizontal saccades reduced mean sway velocity of CoP compared to fixation. Therefore, wearing the eye tracker minimized the body sway of young adults; however, visual task-related effects on postural stability remained unchanged.

Modeling Intensive Polytomous Time-Series Eye-Tracking Data: A Dynamic Tree-Based Item Response Model.

This paper presents a dynamic tree-based item response (IRTree) model as a novel extension of the autoregressive generalized linear mixed effect model (dynamic GLMM). We illustrate the unique utility of the dynamic IRTree model in its capability of modeling differentiated processes indicated by intensive polytomous time-series eye-tracking data. The dynamic IRTree was inspired by but is distinct from the dynamic GLMM which was previously presented by Cho, Brown-Schmidt, and Lee (Psychometrika 83(3):751-771, 2018). Unlike the dynamic IRTree, the dynamic GLMM is suitable for modeling intensive binary time-series eye-tracking data to identify visual attention to a single interest area over all other possible fixation locations. The dynamic IRTree model is a general modeling framework which can be used to model change processes (trend and autocorrelation) and which allows for decomposing data into various sources of heterogeneity. The dynamic IRTree model was illustrated using an experimental study that employed the visual-world eye-tracking technique. The results of a simulation study showed that parameter recovery of the model was satisfactory and that ignoring trend and autoregressive effects resulted in biased estimates of experimental condition effects in the same conditions found in the empirical study.

Fixational microsaccades: A quantitative and objective measure of disability in multiple sclerosis.

BACKGROUND: Objective tools for prognosis and disease progression monitoring in multiple sclerosis (MS) are lacking. The visuomotor system could be used to track motor dysfunction at the micron scale through the monitoring of fixational microsaccades. AIMS: The aim of this study was to evaluate whether microsaccades are correlated with standard MS disability metrics and to assess whether these methods play a predictive role in MS disability. METHOD: We used a custom-built retinal eye tracker, the tracking scanning laser ophthalmoscope (TSLO), to record fixation in 111 participants with MS and 100 unaffected controls. RESULTS: In MS participants, a greater number of microsaccades showed significant association with higher Expanded Disability Status Scale score (EDSS, p < 0.001), nine-hole peg test (non-dominant: p = 0.006), Symbol Digit Modalities Test (SMDT, p = 0.014), and Functional Systems Scores (FSS) including brainstem (p = 0.005), cerebellar (p = 0.011), and pyramidal (p = 0.009). Both brainstem FSS and patient-reported fatigue showed significant associations with microsaccade number, amplitude, and peak acceleration. Participants with MS showed a statistically different average number (p = 0.020), peak vertical acceleration (p = 0.003), and vertical amplitude (p < 0.001) versus controls. Logistic regression models for MS disability were created using TSLO microsaccade metrics and paraclinical tests with ⩾80% accuracy. CONCLUSION: Microsaccades provide objective measurements of MS disability level and disease worsening.