Natural Eye Movements Research Articles

Just-in-time: Gaze guidance in natural behavior.

Natural eye movements have primarily been studied for over-learned activities such as tea-making, sandwich-making, and hand-washing, which have a fixed sequence of associated actions. These studies demonstrate a sequential activation of low-level cognitive schemas facilitating task completion. However, whether these action schemas are activated in the same pattern when a task is novel and a sequence of actions must be planned in the moment is unclear. Here, we recorded gaze and body movements in a naturalistic task to study action-oriented gaze behavior. In a virtual environment, subjects moved objects on a life-size shelf to achieve a given order. To compel cognitive planning, we added complexity to the sorting tasks. Fixations aligned with the action onset showed gaze as tightly coupled with the action sequence, and task complexity moderately affected the proportion of fixations on the task-relevant regions. Our analysis revealed that gaze fixations were allocated to action-relevant targets just in time. Planning behavior predominantly corresponded to a greater visual search for task-relevant objects before the action onset. The results support the idea that natural behavior relies on the frugal use of working memory, and humans refrain from encoding objects in the environment to plan long-term actions. Instead, they prefer just-in-time planning by searching for action-relevant items at the moment, directing their body and hand to it, monitoring the action until it is terminated, and moving on to the following action.

Effects of lorazepam on saccadic eye movements - evidence from prosaccade and free viewing tasks.

Peak velocities of saccadic eye movements are reduced after benzodiazepine administration. Even though this is an established effect, past research has only examined it in horizontal prosaccade tasks. The spectrum of saccadic eye movements, however, is much larger. Therefore, we aimed to make a first attempt at filling this research gap by testing benzodiazepine effects on saccades under different experimental task conditions. 1mg lorazepam or placebo was administered (within-subjects, double-blind, in randomised order) to n = 30 healthy adults. Participants performed an extended version of the prosaccade task, including vertical saccade directions and different stimulus eccentricities, as well as a free viewing task. Results from the prosaccade task confirmed established effects of benzodiazepines as well as saccade direction on saccadic parameters but additionally showed that the drug effect on peak velocity was independent of saccade direction. Remarkably, in the free viewing task peak velocities as well as other saccade parameters were unaffected by lorazepam. Furthermore, exploration patterns during free viewing did not change under lorazepam. Overall, our findings further consolidate the peak velocity of prosaccades as a biomarker of sedation. Additionally, we suggest that sedative effects of low doses of benzodiazepines may be compensated in tasks that more closely resemble natural eye movement behaviour, possibly due to the lack of time constraints or via neurophysiological processes related to volition.

Leyenes: A gaze-based text entry method using linear smooth pursuit and target speed

Gaze-based writing is one of the most widespread eye tracking applications for human–computer interaction. While eye tracking communication has traditionally been employed as an assistive technology, declining prices of eye trackers now make it a feasible alternative to keyboards or touchscreens in many contexts (for example, the interaction with public info points). In this paper we propose Leyenes, a text entry method based on smooth pursuit, a natural eye movement that occurs when the gaze follows a moving target. Our approach requires no explicit calibration by the user, allowing for more spontaneous interaction and enabling eye input even when calibration is difficult to achieve or maintain. To the best of our knowledge, Leyenes is the first text entry technique based on smooth pursuit that considers both (approximate) gaze speed and position and employs a linear interface instead of the more common circular layouts. The results of the user study we conducted show that the proposed solution is slow but robust, with a very low error rate, which makes it particularly suitable for extemporaneous writing of short text.

Eye movements are stable predictors of word reading ability in young readers

During the first years of formal instruction in reading, there are developmental changes to the characteristics of children’s eye movements that correspond to their progress. Generally, these changes are driven by improved text processing and a shift from reliance on sub-lexical to lexical processes. Currently, however, little is known about to what extent early eye movements during reading in ecological contexts account for variations in later word reading ability. In this paper we investigate this association in 164 children in first grade and 206 children in second grade. We recorded their eye movements during normal text passage reading in an unrestricted eye tracking set-up. We analyzed to what extent they account for variation in word reading ability 1 year post-recording, and make comparisons to concurrent predictions. Regression analysis revealed that eye movements accounted for approximately 60% of the variance in concurrent word reading ability and approximately 48% 1 year later. Mean fixation duration explained unique variance in reading ability and largely drives the correlation. Proportion of regressions was not a significant longitudinal predictor among the youngest readers. The difference between the concurrent and longitudinal predictions was greatest in the younger children, which was in line with our expectation. Findings are discussed in relation to current models of word reading. Our results suggest that eye movements are stable predictors of word reading ability. Ultimately, knowledge of what can be gleaned from early readers’ natural eye movements about later word reading ability could help inform assessments of reading development in the educational setting, where the presence of digital assessment tools is growing.

EXAMINATION OF THE CONTROL SYSTEM OF AN ARTIFICIAL EYE IMPLANT

Due to various reasons, a person who is missing one eye may experience psychological as well as excruciating suffering. Enucleation and evisceration surgery are the most often used methods to remove a sick or injured eye. The patient is often fitted with a bespoke implant into the orbital tissues after the surgeon removes the eye. In order to keep the socket from looking hollow and depressed, this replaces volume. Once the socket has stabilized, a prosthetic shell—also known as an artificial eye, glass eye, or ocular prosthesis—is placed within. An ocular implant can mechanically replace the lost eye. There have been significant developments in this field. To replace the missing eye, an ocular prosthesis was developed. Physically, the prosthetic seems natural. The eye, however, is stationary or just slightly mobile. development of an independent ocular motor system is the objective of this study in order to give the artificial eye more realistic movement. The detection of natural eye movement is a crucial issue. This study includes an overview of eye movement detecting techniques. Then eye movement detection using the fusion approach is created. The first aspect that is recorded and stored is the eye movement. Then, during the experiment, the sensor array yields the eye movement signal, and the matching rule yields the eye position. The experimental system, fusion technology, and early findings are covered in the majority of this work. Keywords: Sensor array, fusion, artificial eye, orbital implant, and ocular control.

Using Natural Head Movements to Continually Calibrate EOG Signals.

Electrooculography (EOG) is the measurement of eye movements using surface electrodes adhered around the eye. EOG systems can be designed to have an unobtrusive form-factor that is ideal for eye tracking in free-living over long durations, but the relationship between voltage and gaze direction requires frequent re-calibration as the skin-electrode impedance and retinal adaptation vary over time. Here we propose a method for automatically calibrating the EOG-gaze relationship by fusing EOG signals with gyroscopic measurements of head movement whenever the vestibulo-ocular reflex (VOR) is active. The fusion is executed as recursive inference on a hidden Markov model that accounts for all rotational degrees-of-freedom and uncertainties simultaneously. This enables continual calibration using natural eye and head movements while minimizing the impact of sensor noise. No external devices like monitors or cameras are needed. On average, our method's gaze estimates deviate by 3.54° from those of an industry-standard desktop video-based eye tracker. Such discrepancy is on par with the latest mobile video eye trackers. Future work is focused on automatically detecting moments of VOR in free-living.

Smooth-pursuit performance during Eye-typing from Memory indicates Mental Fatigue.

Mental fatigue is known to occur as a result of activities related to e.g. transportation, health-care, military operations and numerous other cognitive demanding tasks. Gaze tracking has wide-ranging applications, with the technology becoming more compact and processing power reducing. Though numerous techniques have been applied to measure mental fatigue using gaze tracking, smooth-pursuit movement, a natural eye movement generated when following a moving object with gaze, has not been explored with relation to mental fatigue. In this paper, we report the results from a smooth-pursuit movement based eye-typing experiment with varying task difficulty to generate cognitive load, performed in the morning and afternoon by 36 participants. We have investigated the effects of time-on-task and time of day on mental fatigue using self-reported questionnaires and smooth-pursuit performance, extracted from the gaze data. The self-reported mental fatigue increased due to time-on-task, but the time of day did not have an effect. The results illustrate that smooth-pursuit movement performance declined with time-on-task, with increased error in the gaze position and an inability to match the speed of the moving object. The findings exhibit the feasibility of mental fatigue detection using smoothpursuit movements during an eye-interactive task of eye-typing.

Optical phase modulation by natural eye movements: application to time-domain FF-OCT image retrieval.

Eye movements are commonly seen as an obstacle to high-resolution ophthalmic imaging. In this context we study the natural axial movements of the in vivo human eye and show that they can be used to modulate the optical phase and retrieve tomographic images via time-domain full-field optical coherence tomography (TD-FF-OCT). This approach opens a path to a simplified ophthalmic TD-FF-OCT device, operating without the usual piezo motor-camera synchronization. The device demonstrates in vivo human corneal images under the different image retrieval schemes (2-phase and 4-phase) and different exposure times (3.5 ms, 10 ms, 20 ms). Data on eye movements, acquired with a spectral-domain OCT with axial eye tracking (180 B-scans/s), are used to study the influence of ocular motion on the probability of capturing high-signal tomographic images without phase washout. The optimal combinations of camera acquisition speed and amplitude of piezo modulation are proposed and discussed.

Emotional content influences eye-movements under natural but not under instructed conditions

ABSTRACT In everyday life, people can freely decide if and where they would like to move their attention and gaze, often influenced by physical and emotional salience of stimuli. However, many laboratory paradigms explicitly instruct participants when and how to move their eyes, leading to unnatural instructed eye-movements. The current preregistered study compared eye-movements to peripherally appearing faces with happy, angry and neutral expressions under natural and instructed conditions. Participants reliably moved their eyes towards peripheral faces, even when they were not instructed to do so; however, eye-movements were significantly slower under natural than under instructed conditions. Competing central stimuli decelerated eye-movements independently of instructions. Unexpectedly, the emotional salience only affected eye-movements under natural conditions, with faster saccades towards emotional than towards neutral faces. No effects of emotional expression occurred when participants were instructed to move their eyes. The study shows that natural eye-movements significantly differ from instructed eye-movements and emotion-driven attention effects are reduced when participants are artificially instructed to move their eyes, suggesting that research should investigate eye-movements under natural conditions.

Deep learning human action intention classification from natural eye movement patterns

Deep learning human action intention classification from natural eye movement patterns

Overt and covert attention shifts to emotional faces: Combining EEG, eye tracking, and a go/no-go paradigm.

In everyday life, faces with emotional expressions quickly attract attention and eye movements. To study the neural mechanisms of such emotion-driven attention by means of event-related brain potentials (ERPs), tasks that employ covert shifts of attention are commonly used, in which participants need to inhibit natural eye movements towards stimuli. It remains, however, unclear how shifts of attention to emotional faces with and without eye movements differ from each other. The current preregistered study aimed to investigate neural differences between covert and overt emotion-driven attention. We combined eye tracking with measurements of ERPs to compare shifts of attention to faces with happy, angry, or neutral expressions when eye movements were either executed (go conditions) or withheld (no-go conditions). Happy and angry faces led to larger EPN amplitudes, shorter latencies of the P1 component, and faster saccades, suggesting that emotional expressions significantly affected shifts of attention. Several ERPs (N170, EPN, LPC) were augmented in amplitude when attention was shifted with an eye movement, indicating an enhanced neural processing of faces if eye movements had to be executed together with a reallocation of attention. However, the modulation of ERPs by facial expressions did not differ between the go and no-go conditions, suggesting that emotional content enhances both covert and overt shifts of attention. In summary, our results indicate that overt and covert attention shifts differ but are comparably affected by emotional content.

Recovering depth from stereo-input without using any oculomotor information: A computation model

Human beings can perceive depth by using binocular disparity, namely the difference between a stereo-pair of retinal images. It is commonly believed that the visual system requires oculomotor information about the relative orientation between the two eyes to perceive depth on the basis of binocular disparity. Such oculomotor information can be obtained from the efference copy of the oculomotor signal, or it can be derived from the vertical component of the binocular disparity (vertical disparity). Psychophysical studies have shown that stereo depth perception is affected by both the efference copy and by the vertical disparity. But note that any role for the efference signal for spatial perception is limited and the process using vertical disparity is slow. These effects are too restricted to explain depth perception under natural viewing conditions in which natural eye movements are made. In the present study, I describe a computational model that can recover depth from a stereo-pair of retinal images based only on the geometrical optics. This model treats depth recovery as a Direct problem rather than as an Inverse problem because it does not need to make use of any oculomotor information or of any a priori constraints. In this model, oculomotor information is not even implicitly recovered. Simply put, this paper shows that, at least from a computational perspective, oculomotor information and a priori constraints are not actually required for the stereo perception of depth. Having such a model allows us to discuss psychophysical and neurophysiological phenomena, as well as their mechanisms, without assuming that the human visual system needs oculomotor information to recover depth in a 3D scene from stereo retinal images.

Extraction of Nystagmus Patterns from Eye-Tracker Data with Convolutional Sparse Coding.

The analysis of the Nystagmus waveforms from eye-tracking records is crucial for the clinical interpretation of this pathological movement. A major issue to automatize this analysis is the presence of natural eye movements and eye blink artefacts that are mixed with the signal of interest. We propose a method based on Convolutional Dictionary Learning that is able to automatically highlight the Nystagmus waveforms, separating the natural motion from the pathological movements. We show on simulated signals that our method can indeed improve the pattern recovery rate and provide clinical examples to illustrate how this algorithm performs.

Using eye movements to detect visual field loss: a pragmatic assessment using simulated scotoma

Glaucoma is a leading cause of irreversible sight-loss and has been shown to affect natural eye-movements. These changes may provide a cheap and easy-to-obtain biomarker for improving disease detection. Here, we investigated whether these changes are large enough to be clinically useful. We used a gaze-contingent simulated visual field (VF) loss paradigm, in which participants experienced a variable magnitude of simulated VF loss based on longitudinal data from a real glaucoma patient (thereby controlling for other variables, such as age and general health). Fifty-five young participants with healthy vision were asked to view two short videos and three pictures, either with: (1) no VF loss, (2) moderate VF loss, or (3) advanced VF loss. Eye-movements were recorded using a remote eye tracker. Key eye-movement parameters were computed, including saccade amplitude, the spread of saccade endpoints (bivariate contour ellipse area), location of saccade landing positions, and similarity of fixations locations among participants (quantified using kernel density estimation). The simulated VF loss caused some statistically significant effects in the eye movement parameters. Yet, these effects were not capable of consistently identifying simulated VF loss, despite it being of a magnitude likely easily detectable by standard automated perimetry.

A preliminary implementation of an active intraocular prosthesis as a new image acquisition device for a cortical visual prosthesis.

An active intraocular prosthesis is herein proposed as a new image acquisition device for a cortical visual prosthesis. A conventional intraocular prosthesis is a passive device that helps blind patients underwent eye enucleation to maintain the shape of an eyeball. In contrast, an active intraocular prosthesis, which works as an implantable wireless camera, can capture real-time images and transmit them to a cortical visual prosthesis to restore partial vision of the patients. This active device has distinct advantages in that it can garner a variety of image information while focusing on objects in accordance with natural eye movements, compared with a glasses-mounted camera and implanted micro-photodiodes in typical artificial vision systems. Coated with an epoxy and sealed by an elastomer for biocompatibility as well as durability, the active intraocular prosthesis was fabricated in a spherical form miniaturized enough to be inserted into the eye. Its operation was evaluated by wireless image acquisition displaying a processed gray-scale image. Furthermore, signal-to-noise ratio measurements were conducted to find a reliable communication range of the fabricated prosthesis, while it was covered by an 8-mm-thick biological medium that mimicked in vivo environments. In conclusion, the feasibility of the active intraocular prosthesis to cooperate with a cortical visual prosthesis is discussed.

Screen-Light Decomposition Framework for Point-of-Gaze Estimation Using a Single Uncalibrated Camera and Multiple Light Sources

The use of a single uncalibrated camera is desirable for eye tracking to reduce the overall complexity and cost of the system. Quite often, at least one external light source is used to enhance image quality and generate a corneal reflection used as a reference point to estimate the point-of-gaze (PoG). Though the use of more than one light source has shown to enhance accuracy and robustness to head motion, it is unlikely that all corneal reflections appear in the eye images during natural eye movements. In this paper, we introduce the Screen-Light Decomposition (SLD) framework as a generalized model for PoG estimation using a single uncalibrated camera and a variable number of light sources. SLD synthesizes existing uncalibrated video-based eye trackers and can be used as a modeling tool to compare and design eye trackers. We have used the framework to design a novel eye-tracking technique, called SAGE, for single normalized space adaptive gaze estimation, that can gracefully degrade the gaze tracker performance when one or more corneal reflections are not detected, even during the calibration procedure. Results from an user experiment are presented to demonstrate its improved performance over other designs.

GÖZ TAKİP SİSTEMİNİN (EYE TRACKER) SPOR BİLİMİNDE KULLANILMASI: YENİ ARAŞTIRMACILAR İÇİN KILAVUZ

Eye-tracking technology allows special and applied research in sport and exercise psychology field. This technology, already constantly developing, offers thrilling opportunities for natural gaze and eye movement behavior studies of elite and amateur athletes. Though the idea of observing or tracking the eye movements seems simple, the technology behind is quite complicated and sensitive. Also, it necessitates substantial knowledge and experience in both hardware and software. The high cost of eye-tracking and the long time allocated for data analyses requires efficient use of resources. The purpose of this paper is to present basic information to those aiming to study eye-tracking system in the field of sport science. It is expected to help beginners answer the questions considering eye-tracking research and give an idea on how to start.

Biomimetic eye modeling & deep neuromuscular oculomotor control

We present a novel, biomimetic model of the eye for realistic virtual human animation. We also introduce a deep learning approach to oculomotor control that is compatible with our biomechanical eye model. Our eye model consists of the following functional components: (i) submodels of the 6 extraocular muscles that actuate realistic eye movements, (ii) an iris submodel, actuated by pupillary muscles, that accommodates to incoming light intensity, (iii) a corneal submodel and a deformable, ciliary-muscle-actuated lens submodel, which refract incoming light rays for focal accommodation, and (iv) a retina with a multitude of photoreceptors arranged in a biomimetic, foveated distribution. The light intensity captured by the photoreceptors is computed using ray tracing from the photoreceptor positions through the finite aperture pupil into the 3D virtual environment, and the visual information from the retina is output via an optic nerve vector. Our oculomotor control system includes a foveation controller implemented as a locally-connected, irregular Deep Neural Network (DNN), or "LiNet", that conforms to the nonuniform retinal photoreceptor distribution, and a neuromuscular motor controller implemented as a fully-connected DNN, plus auxiliary Shallow Neural Networks (SNNs) that control the accommodation of the pupil and lens. The DNNs are trained offline through deep learning from data synthesized by the eye model itself. Once trained, the oculomotor control system operates robustly and efficiently online. It innervates the intraocular muscles to perform illumination and focal accommodation and the extraocular muscles to produce natural eye movements in order to foveate and pursue moving visual targets. We additionally demonstrate the operation of our eye model (binocularly) within our recently introduced sensorimotor control framework involving an anatomically-accurate biomechanical human musculoskeletal model.

Characterization of natural head and eye movements driving retinal flow

Characterization of natural head and eye movements driving retinal flow

Custom made ocular prosthesis for acquired eye defect:Adefinitive option of rehabilitation

Objective:This case report describes the rehabilitation process of a case of acquired eye defect with patient specific or custom made ocular prosthesis for a patient who had her left eye surgically enucleated as a treatment step for retinoblastoma.
 Method: After primary evaluations, an intraorbital impression was taken while reproducing natural eye movements to ensure accuracy of the impression. The impression was cast and a transparent acrylic conformer was made from the mould in the cast. The conformer was adjusted as required and Iris position determined. The conformer was then used to cast the final custom ocular prosthesis. The patient was then instructed on its usage and maintenance.
 Result: A custom made ocular prosthesis was provided to the patient and it was to her satisfaction.
 Conclusion: Custom made ocular prosthesis is highly recommended in rehabilitation of facial defects of a co-operative patient as it does not have most of the limitations which a stock ocular prosthesis does.
 Bangladesh Journal of Medical Science Vol.18(4) 2019 p.823-826