Eye Movements and Road Hazard Detection: Effects of Blur and Distractors

Seeing the truck, but missing the cyclist: effects of blur on duration thresholds for road hazard detection

Drivers must respond promptly to a wide range of possible road hazards, from trucks veering into their lane to pedestrians stepping onto the road. While drivers' vision is tested at the point of licensure, visual function can degrade, and drivers may not notice how these changes impact their ability to notice and respond to events in the world in a timely fashion. To safely examine the potential consequences of visual degradation on hazard detection, we performed two experiments examining the impact of simulated optical blur on participants' viewing duration thresholds in a hazard detection task, as a proxy for eyes-on-road duration behind the wheel. Examining this question with older and younger participants, across two experiments, we found an overall increase in viewing duration thresholds under blurred conditions, such that younger and older adults were similarly impacted by blur. Critically, in both groups, we found that the increment in thresholds produced by blur was larger for non-vehicular road hazards (pedestrians, cyclists and animals) compared to vehicular road hazards (cars, trucks and buses). This work suggests that blur poses a particular problem for drivers detecting non-vehicular road users, a population considerably more vulnerable in a collision than vehicular road users. These results also highlight the importance of taking into account the type of hazard when considering the impacts of blur on road hazard detection.

Could driving help us to "see better"? A comparative assessment of saccadic efficiency, visual speed, and attention

BACKGROUND

This study aimed at comparing drivers' and non-drivers' results in the Adult Developmental Eye Movement with Distractors test (ADEMd) and the Useful Field of View test (UFOV).

METHODS

One hundred and twenty Spaniards (mean age 50.90 ± 17.32 years) without eye disease voluntarily participated in this cross-sectional descriptive study. Participants in a single experimental session completed a questionnaire on sociodemographic, health, eyesight, and driving information. They also performed the ADEMd and UFOV tests randomly following standardized protocols. The ADEMd is a visual-verbal test that measures saccadic efficiency and visual attention. Brown-Forsythe (B-F) tests with Games-Howell post-hoc adjustments were conducted to assess differences between groups. Groups were formed according to sex, age (young adults, adults, and older adults), and driver/non-driver for further analysis. Additionally, associations between dependent variables were assessed through Spearman's correlations.

RESULTS

Drivers obtained significantly better results in the ADEMd compared with non-drivers. Non-significant differences between drivers and non-drivers were encountered in the UFOV. Additionally, significant differences were observed between sexes and age groups. It is worth highlighting that non-driver's age significantly correlated with worse ADEMd performance (rho = .637 to .716). This correlation was non-significant in drivers. Similarly, reading hours significantly correlated with better ADEMd performance in non-drivers (rho = - .291 to - .363), but not in drivers. The only significant correlations between ADEMd and UFOV tests were found in drivers (rho = .307 to .410).

CONCLUSION

Considering all the discussed results, it could be hypothesized that the driving task promotes abilities, such as oculomotor and cognitive function, which are relevant for the performance in the ADEMd. However, this hypothesis is based on correlational outcomes and further studies should causally assess this possible relation.

Opportunities and Limitations of a Gaze-Contingent Display to Simulate Visual Field Loss in Driving Simulator Studies

Background

Research on task performance under visual field loss is often limited due to small and heterogenous samples. Simulations of visual impairments hold the potential to account for many of those challenges. Digitally altered pictures, glasses, and contact lenses with partial occlusions have been used in the past. One of the most promising methods is the use of a gaze-contingent display that occludes parts of the visual field according to the current gaze position. In this study, the gaze-contingent paradigm was implemented in a static driving simulator to simulate visual field loss and to evaluate parallels in the resulting driving and gaze behavior in comparison to patients.

Methods

The sample comprised 15 participants without visual impairment. All the subjects performed three drives: with full vision, simulated left-sided homonymous hemianopia, and simulated right-sided homonymous hemianopia, respectively. During each drive, the participants drove through an urban environment where they had to maneuver through intersections by crossing straight ahead, turning left, and turning right.

Results

The subjects reported reduced safety and increased workload levels during simulated visual field loss, which was reflected in reduced lane position stability and greater absence of large gaze movements. Initial compensatory strategies could be found concerning a dislocated gaze position and a distorted fixation ratio toward the blind side, which was more pronounced for right-sided visual field loss. During left-sided visual field loss, the participants showed a smaller horizontal range of gaze positions, longer fixation durations, and smaller saccadic amplitudes compared to right-sided homonymous hemianopia and, more distinctively, compared to normal vision.

Conclusion

The results largely mirror reports from driving and visual search tasks under simulated and pathological homonymous hemianopia concerning driving and scanning challenges, initially adopted compensatory strategies, and driving safety. This supports the notion that gaze-contingent displays can be a useful addendum to driving simulator research with visual impairments if the results are interpreted considering methodological limitations and inherent differences to the pathological impairment.

An on-road examination of daytime and evening driving on rural roads: physiological, subjective, eye gaze, and driving performance outcomes

Experiencing sleepiness when driving is associated with increased crash risk. An increasing number of studies have examined on-road driver sleepiness; however, these studies typically assess the effect of sleepiness during the late night or early morning hours when sleep pressure is approaching its greatest. An on-road driving study was performed to assess how a range of physiological and sleepiness measures are impacted when driving during the daytime and evening when moderate sleepiness is experienced. In total, 27 participants (14 women and 13 men) completed a driving session in a rural town lasting approximately 60 minutes, while physiological sleepiness (heart rate variability), subjective sleepiness, eye tracking data, vehicle kinematic data and GPS speed data were recorded. Daytime driving sessions began at 12:00 or 14:00, with the evening sessions beginning at 19:30 or 20:30; only a subset of participants (n = 11) completing the evening sessions (daytime and evening order counterbalanced). The results suggest reductions in the horizontal and vertical scanning ranges occurred during the initial 40 minutes of driving for both daytime and evening sessions, but with evening sessions reductions in scanning ranges occurred across the entire driving session. Moreover, during evening driving there was an increase in physiological and subjective sleepiness levels. The results demonstrate meaningful increases in sleepiness and reductions in eye scanning when driving during both the daytime and particularly in the evening. Thus, drivers need to remain vigilant when driving during the daytime and the evening.

Developing a Screening Tool for Areas of Abnormal Central Vision Using Visual Stimuli With Natural Scene Statistics

Purpose

Previous studies show that some visual field (VF) defects are detectable from visual search behavior; for example, when watching video. Here, we developed and tested a VF testing approach that measures the number of fixations to find targets on a background with spatial frequency content similar to natural scenes.

Methods

Twenty-one older controls and 20 people with glaucoma participated. Participants searched for a Gabor (6 c/°) that appeared in one of 25 possible locations within a 15° (visual angle) 1/f noise background (RMS contrast: 0.20). Procedure performance was assessed by calculating sensitivity and specificity for different combinations of control performance limits (p = 95%, 98%, 99%), number of target locations with fixations outside control performance limits (k = 0 to 25) and number of repeated target presentations (n = 1 to 20).

Results

Controls made a median of two to three fixations (twenty-fifth to seventy-fifth percentile: two to four) to locate the target depending on location. A VF was flagged “abnormal” when the number of fixations was greater than the p = 99% for k = 3 or more locations with n = 2 repeated presentations, giving 85% sensitivity and 95.2% specificity. The median test time for controls was 85.71 (twenty-fifth to seventy-fifth percentile: 66.49–113.53) seconds.

Conclusion

Our prototype test demonstrated effective and efficient screening of abnormal areas in central vision.

Translational Relevance

Visual search behavior can be used to detect central vision loss and may produce results that relate well to performance in natural visual environments.

Comparing oculomotor efficiency and visual attention between drivers and non-drivers through the Adult Developmental Eye Movement (ADEM) test: A visual-verbal test

OBJECTIVE

The objective of this study was to assess and compare drivers' and non-drivers' outcomes in the Adult Developmental Eye Movement test (ADEM), a visual-verbal test that measures the time needed to read series of numbers in both a vertical and horizontal reading pattern. A set of driving parameters (i.e., experience, risk exposure, and day and night perceived difficulty) and demographic variables (i.e., age, gender, and academic level) were considered as potential predictors of the test performance.

METHODS

For this cross-sectional study, 302 healthy subjects (age range 20 to 86 years old) completed a self-reported questionnaire aimed at retrieving data on the independent variables, and underwent the ADEM in order to obtain the dependent outcomes. 214 (70.9%) of the participants were drivers. Non-parametric analyses and multilevel linear regression were used to assess differences between the variables and a prediction model. Also, some correlations were evaluated through the Spearman test.

RESULTS

Drivers showed significantly better test performance than non-drivers. The age, driving experience, and perceived difficulty in driving at night were obtained as potential predictors of the test performance with the applied linear regression model.

CONCLUSION

The ADEM may be a practical, non-expensive, easy-to-apply tool in the assessment of drivers, useful for obtaining or renewing the driving license. This test may help in the detection of impairments in the saccadic efficiency that could have a detrimental effect on the driving performance.

Hazard Perception in Older Drivers With Eye Disease

Purpose

Timely detection of hazards is a key driving skill; however, the hazard perception of drivers with eye disease and related visual changes and the visual predictors of hazard perception are poorly understood.

Methods

Participants included drivers aged 65 years and older with a range of eye diseases, including cataract, age-related maculopathy (AMD), and glaucoma (n = 99; mean age, 75.4 ± 6.4 years) and controls (n = 118; mean age, 72.2 ± 5.5 years). Visual performance was assessed using clinical measures (visual acuity, contrast sensitivity, visual fields) and non-clinical measures (useful field of view, motion sensitivity). Participants completed a computer-based hazard perception test (HPT) that has been related to driving performance and crash risk.

Results

Participants with eye disease exhibited a 0.73-second delay in HPT response times compared to controls (6.61 ± 1.62 seconds vs. 5.88 ± 1.38 seconds; age-adjusted P = 0.012). Participants with glaucoma exhibited significantly delayed responses compared to those with AMD (P = 0.038) and controls (P = 0.004). Poorer motion sensitivity (standardized β = 0.27; P < 0.001), visual acuity (β = 0.21; P = 0.002), and better-eye mean defect (β = –0.17; P = 0.009) were most strongly associated with delayed HPT responses. Motion sensitivity remained significantly associated with HPT responses, adjusted for visual acuity and visual fields.

Conclusions

HPT responses of older drivers with eye disease were delayed compared to controls and translate to an estimated 16-meter longer stopping distance when traveling at 80 km/hr. Decreased motion sensitivity was most strongly associated with delayed HPT responses.

Translational Relevance

HPT tests can provide insight into difficulties regarding road hazard detection of older drivers with eye disease and provide a potential avenue for interventions to improve road safety.

The short-term effects of artificially-impaired binocular vision on driving performance

Appropriate visual function is paramount to ensuring adequate driving performance and road safety. Here, we examined the influence of sudden artificially-impaired binocular vision on driving performance using a car simulator. Twenty-four young drivers (mean age 22.42 ± 3.19 years) drove under three different visual conditions (natural driving, monocular blur, and monocular occlusion) through three different traffic environments with low, medium, and high levels of complexity (highway, rural, and city, respectively). We assessed their driving performance, perceived level of task complexity, and subjectively-experienced road safety. Furthermore, as a manipulation check, we also evaluated the drivers' cardiac vagal responses, as a well-known index of task complexity. The sudden deterioration of binocular vision caused unsafe driving behaviours (distance out of the road and maximum breaking intensity) in the most complex traffic environments. Specific self-regulatory strategies (i.e. increased cardiac vagal responses) and subjective responses corroborated these results. Practitioner summary: This study provides evidence that the sudden deterioration of binocular vision has a detrimental effect on simulated driving performance. Our analysis of cardiovascular functioning shows that drivers adopt self-regulatory strategies when their binocular vision functioning is compromised. Abbreviations: VA: visual acuity; BV: binocular vision; HRV: heart rate variability; NASA: TLX: NASA-Task Load Index; SSS: Stanford Sleepiness scale; RMSSD: root mean square of successive difference; HF: high-frequency.

The Effects of Age, Distraction, and Simulated Central Vision Impairment on Hazard Detection in a Driving Simulator

SIGNIFICANCE

Despite similar levels of visual acuity and contrast sensitivity reductions, simulated central vision impairment increased response times to a much greater extent in older than in younger participants.

PURPOSE

Driving is crucial for maintaining independence in older age, but age-related vision impairments and in-vehicle auditory distractions may impair driving safety. We investigated the effects of age, simulated central vision impairment, and auditory distraction on detection of pedestrian hazards.

METHODS

Thirty-two normally sighted participants (16 younger and 16 older) completed four highway drives in a simulator and pressed the horn whenever they saw a pedestrian. Pedestrians ran toward the road on a collision course with the approaching vehicle. Simulated central vision impairment was achieved by attaching diffusing filters to a pair of laboratory goggles, which reduced visual acuity to 20/80 and contrast sensitivity by 0.35 log units. For drives with distraction, subjects listened to an audiobook and repeated out loud target words.

RESULTS

Simulated central vision impairment had a greater effect on reaction times (660-millisecond increase) than age (350-millisecond increase) and distraction (160-millisecond increase) and had a greater effect on older than younger subjects (828- and 492-millisecond increase, respectively). Simulated central vision impairment decreased safe response rates from 94.7 to 78.3%. Distraction did not, however, affect safety because older subjects drove more slowly when distracted (but did not drive more slowly with vision impairment), suggesting that they might have perceived greater threat from the auditory distraction than the vision impairment.

CONCLUSIONS

Older participants drove more slowly in response to auditory distraction. However, neither older nor younger participants adapted their speed in response to simulated vision impairment, resulting in unsafe detections. These results underline the importance of evaluating safety of responses to hazards as well as reaction times in a paradigm that flexibly allows participants to modify their driving behaviors.

Impact of glaucoma on executive function and visual search

PURPOSE

Executive function and visual search are linked to a number of activities of daily living including driving and mobility. Using a computerised version of the Trail Making Test B (TMT-B), we compared the executive function and visual search ability of older adults with glaucoma to age-similar controls and identified which visual function tests best predict TMT-B performance. Novel low-contrast and shifting-target variations of the test were incorporated to explore the effects of different levels of test complexity.

METHODS

Thirty-one older adults with mild to moderate glaucoma (mean age = 71.2 years [SD 6.9]; better-eye mean deviation [MD]: median = -1.9 dB [IQR = -1.2 to 0.4], worse-eye MD: median = -11.1 dB [IQR = -14.0 to -7.7]) and 24 age-similar controls (mean age = 71.9 years [SD 6.6]) with normal vision participated. The groups were matched in age, sex, and cognitive status (mini-mental state examination [MMSE]). Participants underwent measurements of visual acuity, contrast sensitivity (CS), visual fields, and visual processing speeds using the useful field-of-view (UFoV). Participants then completed four variations of a computerised TMT-B test, with different levels of complexity based on target contrast (high/low-contrast) and shifts in target position (fixed/shifting locations). Linear mixed-effect models were used to explore the effects of group, target contrast and shift on TMT-B completion time.

RESULTS

The glaucoma group took 17.3s longer than controls to complete the TMT-B (P = 0.028). All participants took 6.5s longer to complete the low- compared to the high-contrast tests (P = 0.012), and 10.6s longer for the shifting TMT-B compared to the fixed version (P < 0.001). There was no interaction effect between group, contrast, or target shift on completion time. Across all tests and participant groups, longer completion time was associated with slower UFoV processing speeds (divided attention: P = 0.003; selective attention: P = 0.006). Poorer CS was associated with longer completion times for the low (P = 0.007), but not the high-contrast tests.

CONCLUSIONS

Our findings suggest that older adults with mild to moderate glaucoma have poorer visual search ability and executive function relative to controls. However, decreasing target contrast or shifting target position did not exacerbate the effects of glaucomatous visual impairment on performance. The UFoV was a strong predictor of TMT-B performance.

Eye Movements of Drivers with Glaucoma on a Visual Recognition Slide Test

SIGNIFICANCE

Glaucoma has been shown to impair hazard detection ability and increase crash risk compared to controls. Differences in visual search behavior of the driving scene may explain these differences; however, there has been limited investigation of this issue with inconsistent findings.

PURPOSE

Through eye movement tracking of older drivers with glaucoma, we explored their visual search behavior in comparison with controls while performing the DriveSafe, a slide recognition test purported to predict fitness to drive.

METHODS

Thirty-one drivers with glaucoma (mean age, 71.7 ± 6.3 years; average better-eye mean defect,-3 dB; average worse-eye mean defect,-12 dB) and 25 age-matched controls underwent measurements of their visual acuity, contrast sensitivity, visual fields, and useful field of view (visual processing speeds). Participants' eye movements were recorded while they completed the DriveSafe test, which consists of brief presentations of static, real-world driving scenes containing various road users (pedestrians, bicycles, vehicles). Participants reported the types, positions, and direction of travel of road users in each image; the score was the total number of correctly reported items (maximum, 128).

RESULTS

Drivers with glaucoma had significantly worse DriveSafe scores (P = .03), fixated on road users for shorter durations (P < .001), and exhibited smaller saccades (P = .02) compared with controls. For all participants, longer fixation times on road users (P < .001) was the eye movement measure most strongly associated with better DriveSafe scores; this relationship was not significantly different between groups. Useful field-of-view divided attention was the strongest visual predictor of DriveSafe scores.

CONCLUSIONS

Eye movement changes in the glaucoma group may reflect increased difficulty in identifying relevant objects in the visual scene, which may be related to their lower DriveSafe scores. Given the DriveSafe's potential utility in assessing drivers with visual impairment before on-road testing, further investigations on how DriveSafe performance and eye movement patterns compare to those during on-road driving are warranted.

How are distractibility and hazard prediction in driving related? Role of driving experience as moderating factor

Distraction constitute one of the 'five fatal' behaviours that contribute to road trauma, and some people may be more susceptible to it than others. It is also known that a greater ability to predict danger is related to a lower probability of suffering accidents. It could be hypothesised that drivers with a higher tendency to distraction are worse at predicting traffic hazards, but to what extent might driving experience serve to mitigate this tendency to distraction? The current study collected self-reported attentional errors from drivers by using the Attention-Related Driving Errors Scale (ARDES-Spain) in order to examine whether novice drivers suffered from inattention more than experienced drivers. The results demonstrated that novice drivers scored more highly on ARDES than experienced drivers. ARDES scores were then related to performance in a Hazard Prediction test, where participants had to report what hazard was about to happen in a series of video clips that occlude just as the hazard begins to develop. While experienced drivers were better at the Hazard Prediction test than novice drivers, those participants who reported fewer attention errors were also better able to detect the upcoming hazard following occlusion. In addition, our results demonstrate a relationship between self-reported attentional errors and the ability to predict upcoming hazards on the road, with driving experience having a moderating role. In the case of novice drivers, as their scores in the Manoeuvring Errors ARDES factor increase, their ability in Hazard Prediction diminishes, while for experienced drivers the increase is not significant. Guidance on how to improve training for drivers in order to mitigate the effects of inattention on driving safety can be addressed.

Scanning Behavior and Daytime Driving Performance of Older Adults With Glaucoma

PURPOSE

The purpose of this study was to assess the link between visual scanning behavior and closed-road driving performance in older drivers with glaucomatous visual impairment.

MATERIALS AND METHODS

Participants included 13 older drivers with glaucoma [mean age=71.6±7.1 y; average better-eye mean deviation (MD)=-2.9±2.1 dB, average worse-eye MD=-12.5±7.1 dB] and 10 visually normal controls (mean age=70.6±7.4 y). Visual acuity, contrast sensitivity, visual fields, useful field of view, and motion sensitivity were assessed. Participants drove around a closed-road circuit while their eye movements were recorded with an ASL Mobile Eye-XG, and head movements recorded using the gyroscope sensors of a smart phone. Measures of driving performance included hazards hit, sign recognition, and lane-crossing time; an overall driving score was derived from these component measures.

RESULTS

Participants with glaucoma had significantly poorer overall driving scores (P=0.026) and hit more hazards (P=0.043) than controls. The glaucoma group also exhibited larger saccades (P<0.001) and horizontal (P<0.001) and vertical search variances (P=0.002) than controls. Larger saccades were associated with better driving scores in the glaucoma group (P=0.001), but not the controls (P=0.75). Head movements did not differ between groups. For all participants, better-eye MD was the strongest visual predictor of overall driving score (P<0.001), followed by the other measures of visual fields, motion sensitivity, contrast sensitivity, and useful field of view (P<0.05).

CONCLUSIONS

Older drivers with glaucoma had poorer driving performance than controls and demonstrated differences in eye movement patterns. The association between larger saccades and better driving scores in those with glaucoma suggests that altering scanning behavior may benefit driving performance and safety in this group.

Eye tracking use in researching driver distraction: A scientometric and qualitative literature review approach

Many factors affect road safety, but research constantly shows that drivers are the major cause of critical situations that could potentially lead to a traffic accident in road traffic. Visual information is a crucial part of input information into the driving process; therefore, distractions of overt visual attention can potentially have a large impact on driving safety. Modern eye tracking technology enables researchers to gain precise insight into the direction and movement of a driver’s gaze during various distractions. As this is an evolving and currently very relevant field of road safety research, the present paper sets out to analyse the current state of the research field and the most relevant publications that use eye tracking for research of distractions to a driver’s visual attention. With the use of scientometrics and a qualitative review of the 139 identified publications that fit the inclusion criteria, the results revealed a currently expanding research field. The narrow research field is interdisciplinary in its core, as evidenced by the dispersion of publication sources and research variables. The main research gaps identified were performing research in real conditions, including a wider array of distractions, a larger number of participants, and increasing interdisciplinarity of the field with more author cooperation outside of their primary co-authorship networks.

Effects of simulated mild vision loss on gaze, driving and interaction behaviors in pedestrian crossing situations

PURPOSE

Interaction is the process of behavior adaption between two or more participants primarily based on what they visually perceive. It is an important aspect of traffic participation and supports a safe and efficient flow of traffic. However, prior driving simulator studies investigating the effects of vision impairment have typically used pre-programmed pedestrians that did not interact with the human driver. In the current study we used a linked pedestrian and driving simulator setting to increase the ecological validity of the experimental paradigm. We evaluated the effects of mild vision loss on interactions between drivers and human-controlled, interactive pedestrians compared to preprogrammed, non-interactive pedestrians.

METHOD

Young subjects (mean age 31 years) wore safety goggles with diffusing filters that reduced visual acuity to 20/50 Snellen and contrast sensitivity to 1.49 log units. Two types of crossings (zebra vs. free lane) and two types of pedestrians (non-interactive vs. interactive) were presented to the driver using a multiple simulator setting. Gaze, safety and time series measures were analyzed to quantify the behavior of the participants during the different crossing situations.

RESULTS

Simulated vision impairment significantly increased the time taken to first fixate on the pedestrian, but only had mild adverse effects on safety measures and subsequent interactions. By comparison, pedestrian type and crossing type were found to significantly affect interaction measures. In crossings with the interactive pedestrians the behavior adaption between the driver and the pedestrian took longer and was less correlated in contrast to the situations with the non-interactive pedestrian.

CONCLUSION

Mild vision impairment (slightly worse than the common 20/40 requirement for driving) had little effect on interactions with pedestrians once they were detected and only had mild adverse consequences on driving safety. Time series measures were sensitive to differences in behavior adaption between road users depending on the level of interaction and type of crossing situation.

The effects of auditory satellite navigation instructions and visual blur on road hazard perception

The distracting effects of mobile telephone use while driving are well known, however the effects of other sources of distraction, such as auditory navigation devices, are less well understood. Whether the effects of auditory distraction might interact with other sensory impairments, such as vision impairment, is of interest given that visual impairment is relatively common within the population, particularly as a result of uncorrected refractive error. In this experiment, 20 current drivers (mean age of 29.4 ± 3.2 years), binocularly viewed video recordings of traffic scenes presented as part of the Hazard Perception Test and responded to potential hazards within the traffic scenes. Half of the presented scenes included auditory navigation instructions as an auditory distractor. Additionally, some of the scenes were viewed through optical lenses to induce different levels of refractive blur (+0.50 DS, +1.00 DS and +2.00 DS). Hazard perception response times increased significantly (p < 0.05) with increasing blur. Participants were significantly slower in reacting to hazards for the +1.00 DS and +2.00 DS blur conditions compared to the control condition (with no blur). There was also a significant increase in response times to hazards in the presence of the auditory navigation instructions. The combined effect of blur and auditory instructions was additive, with the worst performance being in the presence of both blur and auditory instructions. These results suggest that the delivery of auditory navigation guidance for those with visual impairments, such as blur, which are relatively common in the population, should be further investigated.

Evaluation of a Paradigm to Investigate Detection of Road Hazards when Using a Bioptic Telescope

SIGNIFICANCE

A new driving simulator paradigm was developed and evaluated that will enable future investigations of the effects of the ring scotoma in bioptic drivers with diverse vision impairments and different telescope designs.

PURPOSE

The ring scotoma may impair detection of peripheral hazards when viewing through a bioptic telescope. To investigate this question, we developed and tested a sign-reading and pedestrian-detection paradigm in a driving simulator.

METHODS

Twelve normally sighted subjects with simulated acuity loss (median 20/120) used a 3.0× monocular bioptic to read 36 road signs while driving in a simulator. Thirteen of 21 pedestrian hazards appeared and ran on the road for 1 second within the ring scotoma while participants were reading signs through the bioptic. Head movements were analyzed to determine whether the pedestrian appeared before or only while using the bioptic. Six subjects viewed binocularly, and six viewed monocularly (fellow eye patched). Two patients with real visual acuity loss in one eye and no light perception in the other performed the same tasks using their own telescopes.

RESULTS

For the monocular simulated acuity loss group, detection rates were significantly higher when the pedestrian appeared before using the bioptic than when it appeared while using the bioptic and was likely within the area of the ring scotoma (77% vs. 28%, P < .001). For the binocular simulated acuity loss group, there was no significant difference in detection rates for pedestrians that appeared before or while using the bioptic (80% vs. 91%, P = .20). The two monocular patients detected only 17% of pedestrians that appeared while looking through the bioptic.

CONCLUSIONS

Our results confirm the utility of the testing paradigm and suggest that the fellow eye of normally sighted observers with simulated acuity loss was able to compensate for the ring scotoma when using a monocular bioptic telescope in a realistic driving task.

Effect of glaucoma on eye movement patterns and laboratory-based hazard detection ability

Purpose

The mechanisms underlying the elevated crash rates of older drivers with glaucoma are poorly understood. A key driving skill is timely detection of hazards; however, the hazard detection ability of drivers with glaucoma has been largely unexplored. This study assessed the eye movement patterns and visual predictors of performance on a laboratory-based hazard detection task in older drivers with glaucoma.

Methods

Participants included 30 older drivers with glaucoma (71±7 years; average better-eye mean deviation (MD) = −3.1±3.2 dB; average worse-eye MD = −11.9±6.2 dB) and 25 age-matched controls (72±7 years). Visual acuity, contrast sensitivity, visual fields, useful field of view (UFoV; processing speeds), and motion sensitivity were assessed. Participants completed a computerised Hazard Perception Test (HPT) while their eye movements were recorded using a desk-mounted Tobii TX300 eye-tracking system. The HPT comprises a series of real-world traffic videos recorded from the driver’s perspective; participants responded to road hazards appearing in the videos, and hazard response times were determined.

Results

Participants with glaucoma exhibited an average of 0.42 seconds delay in hazard response time (p = 0.001), smaller saccades (p = 0.010), and delayed first fixation on hazards (p<0.001) compared to controls. Importantly, larger saccades were associated with faster hazard responses in the glaucoma group (p = 0.004), but not in the control group (p = 0.19). Across both groups, significant visual predictors of hazard response times included motion sensitivity, UFoV, and worse-eye MD (p<0.05).

Conclusions

Older drivers with glaucoma had delayed hazard response times compared to controls, with associated changes in eye movement patterns. The association between larger saccades and faster hazard response time in the glaucoma group may represent a compensatory behaviour to facilitate improved performance.