Aim of this pilot study was to assess the driving performance and its relationship to the visual search behavior, i.e., eye and head movements, of patients with homonymous visual field defects ...(HVFDs) in comparison to healthy-sighted subjects during a simulated driving test. Eight HVFD patients and six healthy-sighted age- and gender-matched control subjects underwent a 40-minute driving test with nine hazardous situations. Eye and head movements were recorded during the drive. Four out of eight patients passed the driving test and showed a driving performance similar to that of the control group. One control group subject failed the test. Patients who passed the test showed an increased number of head and eye movements. Patients who failed the test showed a rightwards-bias in average lane position, probably in an attempt to maximize the safety margin to oncoming traffic. Our study supports the hypothesis that a considerable subgroup of subjects with HVFDs show a safe driving behavior, because they adapt their viewing behavior by increased visual scanning.
In this article a motion cueing algorithm (MCA) based on model predictive control (MPC) for a hexapod-based dynamic driving simulator is derived. The design objective of the MCA is to reproduce the ...real world accelerations and angular velocities for a test person in the simulator while respecting its actuator limitations. This results in an underlying nonlinear, state-constrained optimal control problem. In order to exploit the full predictive potential of the described algorithm, a method to predict the future driver behavior and thus the future desired values for the MPC is derived by modeling the driver as an optimal controller. The OCP weights that mainly influence the predicted driving actions are learned from demonstration using an inverse optimal control (IOC) approach. Furthermore, the direct incorporation of human perception models into the motion planning process is considered. An online driver-in-the-loop experiment with the Daimler driving simulator shows the high potential of the derived MPC scheme compared to the commonly used filter-based approach as well as the efficiency of the underlying optimization method.
The aim of this pilot study was to assess the driving performance and the visual search behavior, that is, eye and head movements, of patients with glaucoma in comparison to healthy-sighted subjects ...during a simulated driving test.
Driving performance and gaze behavior of six glaucoma patients and eight healthy-sighted age- and sex-matched control subjects were compared in an advanced driving simulator. All subjects underwent a 40-minute driving test including nine hazardous situations on city and rural roads. Fitness to drive was assessed by a masked driving instructor according to the requirements of the official German driving test. Several driving performance measures were investigated: lane position, time to line crossing, and speed. Additionally, eye and head movements were tracked and analyzed.
Three out of six glaucoma patients passed the driving test and their driving performance was indistinguishable from that of the control group. Patients who passed the test showed an increased visual exploration in comparison to patients who failed; that is, they showed increased number of head and gaze movements toward eccentric regions. Furthermore, patients who failed the test showed a rightward bias in average lane position, probably in an attempt to maximize the safety margin to oncoming traffic.
Our study suggests that a considerable subgroup of subjects with binocular glaucomatous visual field loss shows a safe driving behavior in a virtual reality environment, because they adapt their viewing behavior by increasing their visual scanning. Hence, binocular visual field loss does not necessarily influence driving safety. We recommend that more individualized driving assessments, which will take into account the patient's ability to compensate, are required.
Purpose
On-road testing
is considered the standard for assessment of driving performance; however, it lacks standardization. In contrast,
driving simulators
provide controlled experimental settings ...in a virtual reality environment. This study compares both testing conditions in patients with binocular visual field defects due to bilateral glaucomatous optic neuropathy or due to retro-chiasmal visual pathway lesions.
Methods
Ten glaucoma patients (PG), ten patients with homonymous visual field defects (PH), and 20 age- and gender-matched ophthalmologically normal control subjects (CG and CH, respectively) participated in a 40-min on-road driving task using a dual brake vehicle. A subset of this sample (8 PG, 8 PH, 8 CG, and 7 CH) underwent a subsequent driving simulator test of similar duration. For both settings, pass/fail rates were assessed by a masked driving instructor.
Results
For
on-road driving
, hemianopia patients (PH) and glaucoma patients (PG) showed worse performance than their controls (CH and CG groups): PH 40%, CH 30%, PG 60%, CG 0%, failure rate. Similar results were obtained for the
driving simulator
test: PH 50%, CH 29%, PG 38%, CG 0%, failure rate. Twenty-four out of 31 participants (77%) showed concordant results with regard to pass/fail under both test conditions (
p
> 0.05; McNemar test).
Conclusions
Driving simulator testing leads to results comparable to on-road driving, in terms of pass/fail rates in subjects with binocular (glaucomatous or retro-chiasmal lesion-induced) visual field defects. Driving simulator testing seems to be a well-standardized method, appropriate for assessment of driving performance in individuals with binocular visual field loss.
•Using sodium (23Na) MRI, we found increased sodium values in the normal appearing grey and white matter in MS patients compared to healthy controls.•Sodium values in T1 hypointense and T1 isointense ...lesions were significantly higher than in the DAWM.•The DAWM showed similar sodium concentrations to the NAWM, suggesting pathological changes less severe than in focal lesions comparable to what is expected in the NAWM.
In multiple sclerosis (MS), magnetic resonance imaging (MRI) frequently shows ill-defined areas with intermediate signal intensity between the normal appearing white matter (NAWM) and focal T2-hyperintense lesions, termed “diffusely appearing white matter” (DAWM). Even though several advanced MRI techniques have shown the potential to detect and quantify subtle commonly not visible microscopic tissue changes, to date only a few advanced MRI studies investigated DAWM changes in a quantitative manner. The aim of this study was to detect and quantify tissue abnormalities in the DAWM in comparison to focal lesions and the NAWM in MS patients by sodium (23Na) MRI.
23Na and conventional MRI were performed in 25 MS patients with DAWM (DAWM+) and in 25 sex- and age matched MS patients without DAWM (DAWM−), as well as in ten healthy controls (HC). Mean total sodium concentrations (TSC) were quantified in the DAWM, NAWM, normal appearing grey matter (NAGM) and in focal MS lesions.
In MS DAWM+and DAWM−, TSC values were increased in the NAGM (DAWM+: 44.61 ± 4.09 mM; DAWM–: 45.37 ± 3.8 mM) and in the NAWM (DAWM+: 39.85 ± 3.89 mM; DAWM–: 39.82 ± 4.25 mM) compared to normal grey and white matter in HC (GM 40.87 ± 3.25 mM, WM 35.9 ± 1.81 mM; p < 0.05 for all comparisons). Interestingly, the DAWM showed similar sodium concentrations (39.32 ± 4.59 mM) to the NAWM (39.85 ± 3.89 mM), whereas TSC values in T1 hypointense (46.53 ± 7.87 mM) and T1 isointense (41.99 ± 6.10 mM) lesions were significantly higher than in the DAWM (p < 0.001 and 0.017 respectively).
23Na MRI is confirmed as a sensitive marker of even subtle tissue abnormalities. DAWM sodium levels are increased and comparable to the abnormalities in NAWM, suggesting pathological changes less severe than in focal lesions comparable to what is expected in the NAWM.
•Eight out of 15 subjects with visual field loss passed a driving test in a simulator.•Simultaneous gaze, heart rate and skin conductance analysis was performed during safety–critical ...situations.•Driver’s eye movements do not reliably reveal whether a traffic hazard was perceived.•Heart rate and especially skin conductance can confirm hazard perception and be used as a complementary method.
The perception of traffic hazards is crucial for timely driving reactions. In this study we examine if the perception of hazardous objects can be determined by means of combined eye-tracking recordings and stress-related indicators in drivers suffering from binocular visual field loss. An increased rate of traffic accidents has been reported for this group of patients, which may lead to driving prohibition. The sole recording of gaze movements may not be sufficient for reliable identification of traffic object perception. Even if a traffic hazard is fixated by the driver, inattention or the presence of higher visual deficits may lead to an inappropriate driving response.
We examined how stress-related indicators, i.e., skin conductance and heart rate, can complement and improve the eye-tracking based analysis of object perception. In a driving simulator study, we assessed the driving performance and hazard perception ability of subjects with binocular visual field loss (eight with homonymous visual field defects and seven with advanced glaucoma) and 15 healthy-sighted control subjects. Seven out of 15 subjects with visual field defects failed the driving assessment, eight passed the test. One healthy-sighted subject failed the driving test.
Drivers with visual field defects showed a significant increase in skin conductance in 93% of situations with adequate reaction to the approaching hazard (69% for heart rate changes. 92% and 81% for healthy drivers, respectively). Furthermore, we identified five out of 120 total situations where the drivers looked at the traffic hazard but failed to react (look-but-not-react). Four of these situations were associated with a change in skin conductance, which can be interpreted as a perceived hazard, but an inadequate behavioral driving response. In one situation, no change in skin conductance was observed (look-but-not-perceived). In eight situations, although drivers did not fixate the traffic hazard, adequate driving reaction was observed. Four of these situations were also associated with changes in skin conductance (perceived-without-look). However, 43% and 44% of all significant increases in skin conductance and heart rate, respectively, occurred without the presence of a traffic hazard.
In summary, our findings suggest that the sole analysis of the driver’s eye movements does not reliably reveal whether a traffic hazard was perceived. Additional recordings of stress-related parameters, such as heart rate, and especially skin conductance, can confirm hazard perception and be used as a complementary method for the evaluation of exploratory eye movements and driving behavior.
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