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A New Method for Assessing the Exploratory Field of View (EFOV)
Abstract
Intact visual functioning is a crucial prerequisite for driving safely. Visual function tests usually include the assessment of the visual acuity and binocular visual field. Based on these results, persons suffering from some types of visual field defects that affect the central 20 degree region are prohibited from driving, although they may have developed patterns of eye and head movements that allow them to compensate for their visual impairment. We propose a new method to assess the exploratory field of view (EFOV), i.e. the field of view of a subject when eye movements are allowed. With EFOV testing we aim at capturing the visual exploration capability of a subject and thus understand the real impact of visual field defects on activities of daily living and potential compensatory strategies.
... More research needs to be conducted to design simple tests that can predict the driving performance of individuals. For example, a new test procedure allowing the assessment of the so-called exploratory field-ofview (EFOV) (i.e, the field-of-view of a person when eye movements are allowed) was introduced in [44]. In contrast to perimetric procedures, during EFOV testing, the subject is encouraged to move the eyes towards the presented stimulus in order to fixate it. ...
Driving vehicles are part of an ultimate technology in modern societies allowing the user to travel and navigate short distances within urban regions as well as long routes within large-scale environments. Thereby, the ability to drive enables us to enlarge our own, biologically defined and restricted range of mobility in a nearly unlimited manner. Driving, that is, controlling a vehicle in a visually cluttered environment, involves the simultaneous use of central and peripheral vision and the execution of primary and secondary tasks (both visual and non-visual). As a vehicle moves through the environment, the visual input is rapidly changing and the driver is therefore often uncertain as to when and where a critical visual event will occur. Consequently, appropriate gaze behavior is a necessary cognitive tool for a safe drive in order to maximize information acquisition together with adequate interpretations and predictions of environmental situations based on memories.
In this chapter, the overall demands of driving are summarized and discussed in relationship with sensory, motor, and cognitive functions. Furthermore, several options to assess driving fitness in real (on-road) and virtual (simulator) environments together with the present regulations concerning the permission to drive are discussed respecting healthy drivers as well as visually impaired hemianopic patients. Finally, conclusions are provided by illustrating the complexity of the task of driving that leads to an overall high variability of behavioral strategies, which is in cause manifested in large individual differences.
... Another potential limitation is that, different from the UFOV, the FVA test evaluates only the central visual function, although the results of both tests are significantly correlated. Tafaj et al. recently reported a new method that goes beyond the typical assessment of the visual functioning [24]. The method measures the visual exploration capability of a subject in order to understand the actual impact of visual field defects on activities of daily living and potential compensatory strategies. ...
Purpose:
To investigate the relationship between the functional visual acuity (FVA) and useful field of view (UFOV) in elderly drivers and assess the usefulness of the FVA test to screen driving aptitude in elderly drivers.
Methods:
This study included 45 elderly drivers (31 men, 14 women; mean age, 68.1 years) and 30 younger drivers (26 men, 4 women; mean age, 34.2 years) who drive regularly. All participants underwent measurement of the binocular corrected distant visual acuity (CDVA), binocular corrected distant FVA (CDFVA), and Visual Field with Inhibitory Tasks Elderly Version (VFIT-EV) to measure UFOV. The tear function and cognitive status also were evaluated.
Results:
The CDVA, the CDFVA, cognitive status, and the correct response rate (CAR) of the VFIT-EV were significantly worse in the elderly group than in the control group (P = 0.000 for all parameters). The cognitive status was correlated significantly with the CDVA (r = -0.301, P = 0.009), CDFVA (r = -0.402, P = 0.000), and the CAR of the VFIT-EV (r = 0.348, P = 0.002) in all subjects. The results of the tear function tests were not correlated with the CDVA, CDFVA, or VFIT-EV in any subjects. Stepwise regression analysis for all subjects in the elderly and control groups showed that the CDFVA predicted the CAR most significantly among the clinical factors evaluated.
Conclusion:
The FVA test is a promising method to screen the driving aptitude, including both visual and cognitive functions, in a short time.
Complex and hazardous driving situations often arise with the delayed perception of traffic objects. To automatically detect whether such objects have been perceived by the driver, there is a need for techniques that can reliably recognize whether the driver’s eyes have fixated or are pursuing the hazardous object. A prerequisite for such techniques is the reliable recognition of fixations, saccades, and smooth pursuits from raw eye tracking data. This chapter addresses the challenge of analyzing the driver’s visual behavior in an adaptive and online fashion to automatically distinguish between fixation clusters, saccades, and smooth pursuits.
In many applications involving scanpath analysis, especially when dynamic scenes are viewed, consecutive fixations and saccades, have to be identified and extracted from raw eye-tracking data in an online fashion. Since probabilistic methods can adapt not only to the individual viewing behavior, but also to changes in the scene, they are best suited for such tasks.
In this paper we analyze the applicability of two types of main-stream probabilistic models to the identification of fixations and saccades in dynamic scenes: (1) Hidden Markov Models and (2) Bayesian Online Mixture Models. We analyze and compare the classification performance of the models on eye-tracking data collected during real-world driving experiments.
This study examined the scanpaths of patients with homonymous hemianopia while viewing naturalistic pictures in their original and also spatially filtered forms. Features of their scanpaths with respect to various saccade and fixation parameters were examined to determine whether they develop compensatory eye movement strategies. The effects of various lesion parameters including location, size, and age on the evolution of such strategies were considered.
Eye movements of eight patients with homonymous hemianopia (four left, four right), but lacking neglect, were recorded while they viewed 22 images of real scenes, and they were compared with the eye movements of eight age matched controls. Subjects viewed each image for 3 seconds, initially in a spatially filtered form in which much of the semantic content had been removed, and then in their unfiltered, original form.
Patients differed significantly from controls in various fixation and saccade parameters. For fixation parameters patients with hemianopia fixated different spatial positions from controls, made more fixations which were more widely distributed and of shorter duration than controls, and spent a greater proportion of their total fixation time in the area corresponding to their blind hemifield. They did not make significantly more refixations than controls. For saccade parameters patients made more saccades into their blind hemifield, these saccades having shorter latencies and shorter amplitudes than those made into their seeing field, and had longer scanpaths than control subjects. The amplitude of their first saccade was longer than that of controls although its direction did not correlate simply with the side of the field defect. Their mean saccade amplitude was similar to that of controls. Filtering out high spatial frequencies within images seemed to accentuate the described differences between eye movement characteristics of hemianopes and controls. Scanpath differences correlated with increasing age but not location or size of lesions causing the hemianopia.
Various features of scanpaths produced by hemianopes were different from normal subjects. These differences correlated with lesion age and may reflect the evolution of a compensatory eye movement strategy.
Clinical Neuro-Ophthalmology is a challenge for residents and experienced clinicians alike. This book covers all relevant techniques of diagnosis as well as interpretations of clinical signs. All information is highly structured, highlighting 'definition', 'note' and 'pearl', so that it can also be used by the physician during the patient encounter. The included flow chart posters remind the physician of the most important information. Further, the accompanying animated CD contains: all of the text passages in a searchable format, interactive case demonstrations, animated sequences of clinical signs and video recordings of clinical examinations. This unique and practical guide offers invaluable and practical advice for physicians treating patients with neuro-ophthalmic problems.
In the past few years, there has been an explosion of eye movement research in cognitive science and neuroscience. This has been due to the availability of 'off the shelf' eye trackers, along with software to allow the easy acquisition and analysis of eye movement data. Accompanying this has been a realisation that eye movement data can be informative about many different aspects of perceptual and cognitive processing. Eye movements have been used to examine the visual and cognitive processes underpinning a much broader range of human activities, including, language production, dialogue, human computer interaction, driving behaviour, sporting performance, and emotional states. Finally, in the past thirty years, there have been real advances in our understanding of the neural processes that underpin eye movement behaviour. The Oxford Handbook of Eye Movements provides a comprehensive review of the entire field of eye movement research. In over fifty articles, it reviews the developments that have so far taken place, the areas actively being researched, and looks at how the field is likely to develop in the coming years. The first section considers historical and background material, before moving onto a second section on the neural basis of eye movements. The third and fourth sections look at visual cognition and eye movements and eye movement pathology and development. The final sections consider eye movements and reading and language processing and eye movements.
The task of automatically tracking the visual attention in dynamic visual scenes is highly challenging. To approach it, we propose a Bayesian online learning algorithm. As the visual scene changes and new objects appear, based on a mixture model, the algorithm can identify and tell visual saccades (transitions) from visual fixation clusters (regions of interest). The approach is evaluated on real-world data, collected from eye-tracking experiments in driving sessions.
Homonymous hemianopia, a consequence of unilateral damage in early visual cortex, is associated with abnormal gaze distributions. However, to date, hemianopic saccade and fixation patterns have been investigated with search tasks and static, two-dimensional displays. The goal of this study was to assess whether abnormal hemianopic gaze patterns also occur when visual tasks are performed under more naturalistic circumstances. We compared fixation patterns of four, long-standing hemianopes with those of four visually-intact controls when immersed in a virtual, three-dimensional environment. Eye position was recorded and categorized under both static and ambulatory conditions. For all conditions tested, hemianopes fixated significantly more frequently into the half of the virtual field of view corresponding to their blind hemifield. But while fixation distributions and dynamics were fairly similar between the two subject groups when subjects were stationary, hemianopic fixation distributions were significantly narrower than those of controls in the walking condition. Our results suggest that hemianopes' compensatory eye movements towards the impaired hemifield when examining static, two-dimensional images also occur in a naturalistic, three-dimensional environment. However, the abnormally narrow range of exploratory fixations observed under ambulatory conditions suggests a potentially maladaptive strategy that could explain many of the difficulties experienced by this patient population when immersed in dynamic, real-life environments.
Neuro-ophthalmology is the subspecialty of medicine concerned with visual disturbances related to the nervous system. Most neuro-ophthalmologists are neurologists or ophthalmologists who have done additional fellowship training in this particular area of study. Typical neuro-ophthalmologic problems include transient visual loss, diplopia, nystagmus, optic neuritis, papilledema, visual field defects, Graves disease, ptosis, and anisocoria. Neuro-ophthalmologists usually receive referrals from general ophthalmologists, neurologists, neurosurgeons, and endocrinologists caring for patients with pituitary tumors and thyroid disease.
The visual input is perhaps the most important sensory information. Understanding its mechanisms as well as the way visual attention arises could be highly beneficial for many tasks involving the analysis of users’ interaction with their environment. We present Vishnoo (Visual Search Examination Tool), an integrated framework that combines configurable search tasks with gaze tracking capabilities, thus enabling the analysis of both, the visual field and the visual attention. Our user studies underpin the viability of such a platform. Vishnoo is an open-source software and is available for download at http://www.vishnoo.de/
We investigated the task-specific role of eye and head movements as a compensatory strategy in patients with homonymous visual field deficits (HVFDs) and in age-matched normal controls. All participants were tested in two tasks, i.e. a dot counting (DC) task requiring mostly simple visual scanning and a cognitively more demanding comparative visual search (CVS) task. The CVS task involved recognition and memory of geometrical objects and their configuration in two test fields. Based on task performance, patients were assigned to one of two groups, "adequate" (HVFD(A)) and "inadequate" (HVFD(I)); the group definitions based on either task turned out to be identical. With respect to the gaze related parameters in the DC task we obtained results in agreement with previous studies: the gaze pattern of HVFD(A) patients and normal controls did not differ significantly, while HVFD(I) patients showed increased gaze movement activity. In contrast, for the more complex CVS task we identified a deviating pattern of compensatory strategy use. Adequately performing subjects, who had used the same gaze strategies as normals in the DC task, now changed to increased gaze movement activity that allowed coping with the increasing task demands. Inadequately performing patients switched to a novel pattern of compensatory behavior in the CVS task. Different compensatory strategies are discussed with respect to the task-specific demands (in particular working memory involvement), the specific behavioral deficits of the patients, and the corresponding brain lesions.
PURPOSE. To report and present data on a method for monitoring patient vigilance during a visual field test by using pupillometry. METHODS. Pupil diameter was recorded at 60 Hz with an eye movement tracking system in 13 patients attending the glaucoma outpatient clinics at Manchester Royal Eye Hospital. The patients were instructed to fixate a central target and to press a response button when they saw a stimulus that was randomly presented 5 degrees to the left or right of fixation. A repetitive up/down bracketing strategy was used (1-dB steps, 2-second interstimulus intervals, 10-minute duration) at these two locations. Wavelet analysis was used to extract a denoised measure of the pupil diameter and the amplitude of any pupillary fatigue waves. The relationship between the probability of seeing a stimulus and these two components of the pupil response was investigated. RESULTS. Good pupil data were obtained from 12 patients. Most (8/12) showed gradual miosis and periods of pupillary fatigue waves during the recording session. Pupillary fatigue waves became more evident with test duration, and the probability of seeing a stimulus was higher when the pupil was dilated (P < 0.001) and the amplitude of the papillary fatigue waves was low (P < 0.001). CONCLUSIONS. Pupil miosis and fatigue wave amplitude are related to vigilance in patients who take a perimetric-type test. Pupillography can be used to investigate vigilance and how it contributes to perimetric variability.
The major studies on the inter-relationship between visual performance and road accident records are briefly reviewed. Statutory standards of vision for vehicle drivers are discussed, together with the responsibilities of the driver, Licensing Authority and those offering advice to drivers on their standards of vision.
The gaze behavior of homonymous hemianopes differs from that of visually intact observers when performing simple laboratory tasks. To test whether such compensatory behavior is also evident during naturalistic tasks, we analyzed the gaze patterns of three long-standing hemianopes and four visually intact controls while they assembled wooden models. No significant differences in task performance, saccade dynamics or spatial distribution of gaze were observed. Hemianopes made more look-ahead fixations than controls and their gaze sequences were less predictable. Thus hemianopes displayed none of the compensatory gaze strategies seen in laboratory tasks. Instead, their gaze patterns suggest greater updating of, and greater reliance on a spatial representation.
Knowing the users point of gaze has significant potential to enhance current human-computer interfaces, given that eye movements can be used as an indicator of the attentional state of a user. The primary obstacle of integrating eye movements into todays interfaces is the availability of a reliable, low-cost open-source eye-tracking system. Towards making such a system available to interface designers, we have developed a hybrid eye-tracking algorithm that integrates feature-based and model-based approaches and made it available in an open-source package. We refer to this algorithm as "starburst" because of the novel way in which pupil features are detected. This starburst algorithm is more accurate than pure feature-based approaches yet is signi?cantly less time consuming than pure modelbased approaches. The current implementation is tailored to tracking eye movements in infrared video obtained from an inexpensive head-mounted eye-tracking system. A validation study was conducted and showed that the technique can reliably estimate eye position with an accuracy of approximately one degree of visual angle.