Driving with homonymous visual field loss: a review of the literature

Vision-related quality of life after unilateral occipital stroke

BACKGROUND/OBJECTIVES

Stroke damage to the primary visual cortex induces large, homonymous visual field defects that impair daily living. Here, we asked if vision-related quality of life (VR-QoL) is impacted by time since stroke.

SUBJECTS/METHODS

We conducted a retrospective meta-analysis of 95 occipital stroke patients (female/male = 26/69, 27-78 years old, 0.5-373.5 months poststroke) in whom VR-QoL was estimated using the National Eye Institute Visual Functioning Questionnaire (NEI-VFQ) and its 10-item neuro-ophthalmic supplement (Neuro10). Visual deficit severity was represented by the perimetric mean deviation (PMD) calculated from 24-2 Humphrey visual fields. Data were compared with published cohorts of visually intact controls. The relationship between VR-QoL and time poststroke was assessed across participants, adjusting for deficit severity and age with a multiple linear regression analysis.

RESULTS

Occipital stroke patients had significantly lower NEI-VFQ and Neuro10 composite scores than controls. All subscale scores describing specific aspects of visual ability and functioning were impaired except for ocular pain and general health, which did not differ significantly from controls. Surprisingly, visual deficit severity was not correlated with either composite score, both of which increased with time poststroke, even when adjusting for PMD and age.

CONCLUSIONS

VR-QoL appears to improve with time postoccipital stroke, irrespective of visual deficit size or patient age at insult. This may reflect the natural development of compensatory strategies and lifestyle adjustments. Thus, future studies examining the impact of rehabilitation on daily living in this patient population should consider the possibility that their VR-QoL may change gradually over time, even without therapeutic intervention.

Knowing me, knowing you-A study on top-down requirements for compensatory scanning in drivers with homonymous visual field loss

OBJECTIVE

It is currently still unknown why some drivers with visual field loss can compensate well for their visual impairment while others adopt ineffective strategies. This paper contributes to the methodological investigation of the associated top-down mechanisms and aims at validating a theoretical model on the requirements for successful compensation among drivers with homonymous visual field loss.

METHODS

A driving simulator study was conducted with eight participants with homonymous visual field loss and eight participants with normal vision. Participants drove through an urban surrounding and experienced a baseline scenario and scenarios with visual precursors indicating increased likelihoods of crossing hazards. Novel measures for the assessment of the mental model of their visual abilities, the mental model of the driving scene and the perceived attention demand were developed and used to investigate the top-down mechanisms behind attention allocation and hazard avoidance.

RESULTS

Participants with an overestimation of their visual field size tended to prioritize their seeing side over their blind side both in subjective and objective measures. The mental model of the driving scene showed close relations to the subjective and actual attention allocation. While participants with homonymous visual field loss were less anticipatory in their usage of the visual precursors and showed poorer performances compared to participants with normal vision, the results indicate a stronger reliance on top-down mechanism for drivers with visual impairments. A subjective focus on the seeing side or on near peripheries more frequently led to bad performances in terms of collisions with crossing cyclists.

CONCLUSION

The study yielded promising indicators for the potential of novel measures to elucidate top-down mechanisms in drivers with homonymous visual field loss. Furthermore, the results largely support the model of requirements for successful compensatory scanning. The findings highlight the importance of individualized interventions and driver assistance systems tailored to address these mechanisms.

Interpretation of the Visual Field in Neuro-ophthalmic Disorders

PURPOSE OF REVIEW

In this review, we will describe current methods for visual field testing in neuro-ophthalmic clinical practice and research, develop terminology that accurately describes patterns of field deficits, and discuss recent advances such as augmented or virtual reality-based perimetry and the use of artificial intelligence in visual field interpretation.

RECENT FINDINGS

New testing strategies that reduce testing times, improve patient comfort, and increase sensitivity for detecting small central or paracentral scotomas have been developed for static automated perimetry. Various forms of machine learning-based tools such as archetypal analysis are being tested to quantitatively depict and monitor visual field abnormalities in optic neuropathies. Studies show that the combined use of optical coherence tomography and standard automated perimetry to determine the structure-function relationship improves clinical care in neuro-ophthalmic disorders. Visual field assessment must be performed in all patients with neuro-ophthalmic disorders affecting the afferent visual pathway. Quantitative visual field analysis using standard automated perimetry is critical in initial diagnosis, monitoring disease progression, and guidance of therapeutic plans. Visual field defects can adversely impact activities of daily living such as reading, navigation, and driving and thus impact quality of life. Visual field testing can direct appropriate occupational low vision rehabilitation in affected individuals.

UK exceptional case driving application outcomes in post-stroke homonymous hemianopia: results from a clinical study

PURPOSE

We report results in relation to returning to driving in the UK under the exceptional cases rule for visual field loss.

METHODS

The Hemianopia Adaptation Study is a prospective clinical study recruiting adult stroke survivors with new onset homonymous hemianopia. The mobility assessment course (MAC) was used to measure navigational scanning. Car drivers were offered a 1-year post-stroke assessment to consider referral for driving assessment.

RESULTS

Of 144 participants, 51 were eligible for driving assessment, with 13 (25.4%) accepting appointment for UK Driving and Vehicle Licensing Agency (DVLA) referral. A statistically significant difference in gender and baseline Barthel (stroke severity) scores was found between those requesting referral and those declining (p = 0.046; p < 0.001). MAC outcomes were significantly different, with those referred having a lower percentage of target omissions (9.0%) and faster mean course completion time (46.0 s), than those not referred (28.3%/72.5 s) (p = 0.006/p < 0.001). Twelve of the 13 referred were offered a driving assessment by the DVLA. All 12 passed and returned to driving.

CONCLUSIONS

It is possible for individuals with post-stroke homonymous hemianopia to return to driving, where exceptional cases criteria are met. There is evidence to support use of the MAC as a clinical measurement of adaptation.IMPLICATIONS FOR REHABILITATIONIndividuals with post-stroke homonymous hemianopia should be fully informed regarding driving regulations that can differ between countries and sometimes different states within a country, as well as provided with the support and opportunity to consider a return to driving if appropriate.Professionals providing care within the stroke multi-disciplinary team should be aware that it is possible for patients with homonymous hemianopia to return to driving, when exceptional cases criteria are met.The mobility assessment course (MAC) should be considered as a clinical measurement of adaptation in homonymous hemianopia.A cut-off score of ≤25% omissions on MAC could be employed to determine those likely to adapt to hemianopia long-term and potentially return to driving.

The effect of visual rivalry in peripheral head-mounted displays on mobility

Recent head-mounted displays and smart glasses use vision multiplexing, an optical approach where two or more views are superimposed on each other. In vision multiplexing, augmented information is presented over an observer's natural field of view, providing field expansion and critical information during mobility situations like walking and driving. Yet despite its utility, vision multiplexing may produce visual rivalry, a phenomenon where perception alternates between the augmented information and the background scene for seconds at a time. To investigate, we compared the effect of different peripheral vision multiplexing configurations (unilateral opaque, unilateral see-through and bilateral see-through) on the detection of augmented information, incorporating at the same time real-world characteristics (target eccentricity, depth condition, and gaze movement) for a more realistic assessment. Results showed a persistently lower target detection rate in unilateral configurations than the bilateral configuration, suggesting a larger effect of binocular rivalry on target visibility. Nevertheless, this effect does become attenuated when more naturalistic elements are incorporated, and we discuss recommendations for vision multiplexing design and possible avenues for further research.

Perceptual-Cognitive Integration for Goal-Directed Action in Naturalistic Environments

Real-world actions require one to simultaneously perceive, think, and act on the surrounding world, requiring the integration of (bottom-up) sensory information and (top-down) cognitive and motor signals. Studying these processes involves the intellectual challenge of cutting across traditional neuroscience silos, and the technical challenge of recording data in uncontrolled natural environments. However, recent advances in techniques, such as neuroimaging, virtual reality, and motion tracking, allow one to address these issues in naturalistic environments for both healthy participants and clinical populations. In this review, we survey six topics in which naturalistic approaches have advanced both our fundamental understanding of brain function and how neurologic deficits influence goal-directed, coordinated action in naturalistic environments. The first part conveys fundamental neuroscience mechanisms related to visuospatial coding for action, adaptive eye-hand coordination, and visuomotor integration for manual interception. The second part discusses applications of such knowledge to neurologic deficits, specifically, steering in the presence of cortical blindness, impact of stroke on visual-proprioceptive integration, and impact of visual search and working memory deficits. This translational approach-extending knowledge from lab to rehab-provides new insights into the complex interplay between perceptual, motor, and cognitive control in naturalistic tasks that are relevant for both basic and clinical research.

Oblique multi-periscopic prism for field expansion of homonymous hemianopia

Oblique Fresnel peripheral prisms have been used for field expansion in homonymous hemianopia mobility such as walking and driving. However, limited field expansion, low image quality, and small eye scanning range limit their effectiveness. We developed a new oblique multi-periscopic prism using a cascade of rotated half-penta prisms, which provides 42° horizontal field expansion along with 18° vertical shift, high image quality, and wider eye scanning range. Feasibility and performance of a prototype using 3D-printed module are demonstrated by raytracing, photographic depiction, and Goldmann perimetry with patients with homonymous hemianopia.

Peripheral visual field loss and activities of daily living

PURPOSE OF REVIEW

Peripheral visual field (VF) loss affects 13% of the population over 65. Its effect on activities of daily living and higher order visual processing is as important as it is inadequately understood. The purpose of this review is to summarize available literature on the impact of peripheral vision loss on driving, reading, face recognition, scene recognition and scene navigation.

RECENT FINDINGS

In this review, glaucoma and retrochiasmal cortical damage are utilized as examples of peripheral field loss which typically spare central vision and have patterns respecting the horizontal and vertical meridians, respectively. In both glaucoma and retrochiasmal damage, peripheral field loss causes driving difficulty - especially with lane maintenance - leading to driving cessation, loss of independence, and depression. Likewise, peripheral field loss can lead to slower reading speeds and decreased enjoyment from reading, and anxiety. In glaucoma and retrochiasmal field loss, face processing is impaired which impacts social functioning. Finally, scene recognition and navigation are also adversely affected, impacting wayfinding and hazard detection leading to decreased independence as well as more frequent injury.

SUMMARY

Peripheral VF loss is an under-recognized cause of patient distress and disability. All peripheral field loss is not the same, differential patterns of loss affect parameters of activities of daily living (ADL) and visual processing in particular ways. Future research should aim to further characterize patterns of deranged ADL and visual processing, their correlation with types of field loss, and associated mechanisms.

The effects of visual-field loss from panretinal photocoagulation of proliferative diabetic retinopathy on performance in a driving simulator

BACKGROUND

The purpose of this study was to compare driving-simulator performance of participants with visual-field loss (VFL) from panretinal photocoagulation (PRP) of proliferative diabetic retinopathy (PDR) with a normally sighted control group. Furthermore, we investigated the effects of VFL of different extent on driving.

METHODS

Data on performance and safety from a traffic-simulator test for 27 participants with VFL from PRP of PDR were retrospectively compared with data from 83 individuals without visual deficits in a cross-sectional study. Individuals with diabetes that regained their driving licences after a successful simulator test were then followed in a national accident database.

RESULTS

Diabetes participants passed the test in 56% of the cases. Compared with the control group, diabetes participants had more risky "failed to give way" events and longer reaction times. Failed diabetes participants had lower mean sensitivity in the superior visual field than those who passed. None of the participants with a regained licence were involved in a motor vehicle accident during the 3-6-year follow-up after the simulator test.

CONCLUSIONS

Diabetes participants had worse performance and safety than the controls. However, even individuals with VFL from PRP might drive safely, which highlights the need for individual assessments in licencing issues.

Visual disorders and driving ability in persons with dementia: A mini review

Background

Impaired driving ability in patients with Alzheimer’s disease (AD) is associated with a decline in cognitive processes and a deterioration of their basic sensory visual functions. Although a variety of ocular abnormalities have been described in patients with AD, little is known about the impact of those visual disorders on their driving performance.

Aim

Aim of this mini-review is to provide an update on the driving ability of patients with dementia and summarize the primary visual disorders affecting their driving behavior.

Methods

Databases were screened for studies investigating dementia, associated visual abnormalities and driving ability.

Results

There is consistent evidence that dementia affects driving ability. Patients with dementia present with a variety of visual disorders, such as visual acuity reduction, visual field defects, impaired contrast sensitivity, decline in color vision and age-related pathological changes, that may have a negative impact on their driving ability. However, there is a paucity in studies describing the impact of oculovisual decline on the driving ability of AD subjects. A bidirectional association between cognitive and visual impairment (VI) has been described.

Conclusion

Given the bidirectional association between VI and dementia, vision screening and cognitive assessment of the older driver should aim to identify at-risk individuals and employ timely strategies for treatment of both cognitive and ocular problems. Future studies should characterize the basic visual sensory status of AD patients participating in driving studies, and investigate the impact of vision abnormalities on their driving performance.

Comparison of visual requirements and regulations for obtaining a driving license in different European countries and some open questions on their adequacy

We reviewed the current state of knowledge regarding visual function and its suitability as part of medical examinations for driving licenses. We focused only on Group 1 drivers. According to previous studies, visual acuity, which is the most common test, is weakly associated with a higher risk of road accidents, with a greater role of visual field. The inclusion of the visual field test in medical examinations is therefore important, but the actual limit value is still unclear and further research in specific situations is needed. Color vision impairment was not found a threat to traffic safety. Contrast sensitivity decreases with age and is affected by abnormal eye conditions. Resulting glare can lead to an increased risk of traffic accidents during night driving in the elderly and others with conditions that impair contrast sensitivity. However, the universal cut-off limits have not been established either. The current European Union (EU) regulations therefore reflect minimum common denominator across the member states which may not entirely translate to optimal driving safety. Due to these open questions, standardized testing in simulators or on polygons that simulate real life conditions would be needed to better determine safe limits of visual function in different conditions. As there is a need to have better standardization across Europe regarding the requirements and rules regarding driving licenses in European countries, we first analyzed existing rules and compared them with each other, also in terms of deviations from the EU directive itself. We reviewed the literature in this field and prepared proposals for a more optimal regulation of the rules in the future. Particular attention is paid to the new method of examining the visual field that was created to respect the European directive. The paper can serve as a basis of information for research teams to design further protocols, as it gathers research findings to date on the importance and impact of various visual functions on driving safety, as well as a starting point for a debate on revising existing rules for obtaining and maintaining licenses, as it compares the current regulations in European countries and differences between them.

The Effects of Visual Field Loss from Stroke on Performance in a Driving Simulator

SIGNIFICANCE

Visual field loss (VFL) is a common consequence of stroke and often precludes driving. However, legal visual requirements for drivers' licenses are largely without scientific basis.

PURPOSE

To examine the effects of different types of homonymous VFL after stroke on simulated driving.

METHODS

Data on performance and safety from a traffic simulator test for 153 participants with withdrawn drivers' licenses due to visual field loss from stroke was retrospectively compared with data from 83 healthy individuals without visual deficits in a cross-sectional study. The 93 individuals in the stroke group that regained their driving licenses after a successful simulator test were then followed in a national accident database.

RESULTS

Sixty-five per cent of the stroke participants passed the simulator test (95% confidence interval 57-72%). Younger patients were more successful than older. However, neither classification by type of homonymous visual field loss, nor by side of visual field loss was predictive of driver safety. Participants with hemianopia had their lateral lane position dislocated to the non-affected side of the visual field. None of the participants with a regained license were involved in motor vehicle accidents three to six years after the test.

CONCLUSIONS

In this large cohort, driver safety could not be predicted from the type of homonymous visual field loss. Even individuals with severe visual field loss might be safe drivers. Therefore, it seems reasonable to provide an opportunity for individualized assessments of practical fitness to drive in circumstances of licensing issues. This study demonstrates the potential of using a standardized driving simulator test for such assessments of fitness to drive.

Driving With Hemianopia X: Effects of Cross Traffic on Gaze Behaviors and Pedestrian Responses at Intersections

Purpose

We conducted a driving simulator study to investigate the effects of monitoring intersection cross traffic on gaze behaviors and responses to pedestrians by drivers with hemianopic field loss (HFL).

Methods

Sixteen HFL and sixteen normal vision (NV) participants completed two drives in an urban environment. At 30 intersections, a pedestrian ran across the road when the participant entered the intersection, requiring a braking response to avoid a collision. Intersections with these pedestrian events had either (1) no cross traffic, (2) one approaching car from the side opposite the pedestrian location, or (3) two approaching cars, one from each side at the same time.

Results

Overall, HFL drivers made more (p < 0.001) and larger (p = 0.016) blind- than seeing-side scans and looked at the majority (>80%) of cross-traffic on both the blind and seeing sides. They made more numerous and larger gaze scans (p < 0.001) when they fixated cars on both sides (compared to one or no cars) and had lower rates of unsafe responses to blind- but not seeing-side pedestrians (interaction, p = 0.037). They were more likely to demonstrate compensatory blind-side fixation behaviors (faster time to fixate and longer fixation durations) when there was no car on the seeing side. Fixation behaviors and unsafe response rates were most similar to those of NV drivers when cars were fixated on both sides.

Conclusion

For HFL participants, making more scans, larger scans and safer responses to pedestrians crossing from the blind side were associated with looking at cross traffic from both directions. Thus, cross traffic might serve as a reminder to scan and provide a reference point to guide blind-side scanning of drivers with HFL. Proactively checking for cross-traffic cars from both sides could be an important safety practice for drivers with HFL.

Driving and exceptional cases: Supporting relicensing evaluation in patients whose visual fields fail to meet standards

PURPOSE

The UK Driver and Vehicle Licensing Agency's (DVLA) visual field criteria mean that homonymous defects close to fixation are not usually acceptable for driving. Here, we illustrate cases where patients with field defects failing to meet standards had their licences revoked but subsequently were permitted to drive again through exceptional case provisions.

METHODS

Clinical assessment of two patients with homonymous loss: a 62-year-old man (PWT) with a dense left upper homonymous quadrantanopia secondary to a right occipital lobe stroke and a 48-year-old woman (JC), only aware of right upper homonymous quadrantanopia following routine primary care assessment and subsequently attributed to left middle cerebral artery stroke from perinatal intracranial haemorrhage.

RESULTS

PWT's Esterman test showed a significant central defect failing to meet the standard. His subsequent ophthalmic examination was otherwise unremarkable with excellent visual functions. Clinical evidence was provided supporting his relicensing application, and in time, a practical DVLA driving assessment indicated adaptation had been successful, and his licence was restored. JC's defect also failed to meet the standard, and her licence was revoked. Her ophthalmic examination was otherwise unremarkable, and her condition was attributed to a nonprogressive, isolated perinatal event. The DVLA accepted supporting clinical evidence; her subsequent practical driving assessment demonstrated successful adaptation and her licence was also restored.

CONCLUSIONS

Conventional visual field tests are not necessarily predictive of real-world driving performance, with drivers' adaptive strategies not being accommodated. In the UK, individuals with visual field loss failing to meet the standard may be eligible for relicensing as exceptional cases if specific criteria can be met. For exceptional cases potentially licensable under these criteria, the DVLA requires clinician support and a satisfactory practical driving assessment. Similar provisions exist internationally. Clinicians need to be aware of the role they may play in such scenarios.

Mild-to-Moderate Traumatic Brain Injury: A Review with Focus on the Visual System

Traumatic Brain Injury (TBI) is a major global public health problem. Neurological damage from TBI may be mild, moderate, or severe and occurs both immediately at the time of impact (primary injury) and continues to evolve afterwards (secondary injury). In mild (m)TBI, common symptoms are headaches, dizziness and fatigue. Visual impairment is especially prevalent. Insomnia, attentional deficits and memory problems often occur. Neuroimaging methods for the management of TBI include computed tomography and magnetic resonance imaging. The location and the extent of injuries determine the motor and/or sensory deficits that result. Parietal lobe damage can lead to deficits in sensorimotor function, memory, and attention span. The processing of visual information may be disrupted, with consequences such as poor hand-eye coordination and balance. TBI may cause lesions in the occipital or parietal lobe that leave the TBI patient with incomplete homonymous hemianopia. Overall, TBI can interfere with everyday life by compromising the ability to work, sleep, drive, read, communicate and perform numerous activities previously taken for granted. Treatment and rehabilitation options available to TBI sufferers are inadequate and there is a pressing need for new ways to help these patients to optimize their functioning and maintain productivity and participation in life activities, family and community.

Change blindness in simulated driving in individuals with homonymous visual field loss

Individuals with homonymous visual field loss (HVFL) fail to perceive visual information that falls within the blind portions of their visual field. This places additional burden on memory to represent information in their blind visual field, which may make visual changes in the scene more difficult to detect. Failing to detect changes could have serious implications in the context of driving. A change blindness driving simulator experiment was conducted with individuals with HVFL (n = 17) and in those with normal vision (NV; n = 16) where changes (pedestrians appearing) were triggered based on the driver’s gaze location. Gaze was used to ensure that the location of the change was visible before and after the change occurred. There were wide individual differences in both vision groups, ranging from no change blindness to more than 33% of events. Those with HVFL had more change blindness than those with NV (16.7% vs. 6.3%, p < 0.001) and more change blindness to pedestrians appearing in their blind than seeing hemifield (34.6% vs. 10.4%, p < 0.001). Further, there was more change blindness for events appearing in the seeing hemifield for those with HVFL than normal vision (p = 0.023). These results suggest that individuals with HVFL may be more susceptible to failures of awareness, such as change blindness, than individuals with normal vision. Increased risk for failures of awareness may result in motor vehicle crashes where the driver fails to notice the other road user (looked-but-failed-to-see incidents).

Comparison of vision-related quality of life in patients with homonymous hemianopia and monocular blindness

To evaluate the vision-related quality of life (QoL) in patients with homonymous hemianopia (HH). The study compared the QoL in 32 patients with HH and 33 patients with monocular blindness. Best-corrected visual acuity (BCVA) and visual field test were investigated. The National Eye Institute-Visual Function Questionnaire 25 (NEI VFQ-25) and independent mobility questionnaires (IMQs) were used to assess their perceived visual and physical functioning abilities. The results of QoL questionnaires were compared in two groups. The mean deviation (MD) in the better eye was significantly lower in the HH group than in the monocular blindness group. The composite scores of NEI-VFQ and IMQs were significantly lower in the HH patients than in the monocular blindness patients. The driving-related score was significantly lower in patients with right hemianopsia than in those with left hemianopsia. The outdoor activity-related score was significantly lower in patients aged less than 55 years than in patients aged 55 years and more. Homonymous hemianopia had a negative impact on patients’ QoL by limiting their vision related activities compared to monocular blindness. The MD of the better eye in the HH patients reflects the binocular visual field and can affect the real visual function and QoL.

Self-Perception and the Relation to Actual Driving Abilities for Individuals With Visual Field Loss

Background

In Sweden, individuals with visual field loss (VFL) have their driving license withdrawn. The literature clearly indicates that individuals with VFL are unsafe drivers on a group level. However, many drivers with VFL can be safe on an individual level. The literature also suggests that self-perception, beliefs, and insights of one’s own capabilities are related to driving performance. This study had three aims: (1) To investigate self-perceived driving capability ratings for individuals with VFL; (2) to compare these ratings between groups with different medical conditions associated with VFL (stroke, glaucoma, and diabetes); and (3) to relate the self-perception ratings to actual driving performance in an advanced driving simulator.

Methods

Participants comprised 723 individuals whose driver’s license had been withdrawn because of VFL and 92 normally sighted elderly individuals. All participants completed a background survey, rated difficulties with different traffic situations, rated their strengths and weaknesses as drivers, and rated aspects that were important for causing traffic accidents. Of the VFL group participants, 264 also completed a simulator-based driving test that they knew could lead to renewal of their driving license. VFL participants and normally sighted was at the same age when they completed the simulator driving test.

Results

Overall, individuals with VFL rated their capabilities as high on all instruments and scales used, even higher than the elderly normally sighted control group. The only VFL etiology group that rated lower than other groups was the diabetes group. Safety orientation and internal control orientation values were best at discriminating between VFL participants in terms of self-perception of driving performance. Participants categorized as “high” in terms of safety skills and internal control were more modest in their ratings. Finally, participants who passed the simulated driving test did not differ from those who failed, in any of the self-perception measures.

Conclusion

Self-perception ratings among individuals with VFL were higher than those of normally sighted elderly individuals. Self-assessed skills did not predict driving performance. Groups with different VFL etiologies rated similarly. Self-ratings of driving abilities cannot be used to assess actual driving performance. Actual driving tests (on road or in the simulator) are necessary to discriminate between safe and unsafe drivers with VFL.

Binocular Visual Field and Vision-Related Quality of Life in Patients With Hemianopia

BACKGROUND

Hemianopias can have a severe impact on functional ability and quality of life (QoL). Binocular visual field (VF) analysis is clinically more relevant to visual function than monocular VF. The aim is to analyze the binocular VF of patients with hemianopias and its association with the monocular VF and to assess the QoL of these patients through questionnaires specifically related to vision compared with healthy controls.

METHODS

The case-control study included patients with hemianopias and controls. Sex, age, general history, etiology, location of the lesion, and time since the lesion appeared were recorded. Monocular VF and Esterman binocular VF were performed. VF defect, mean defect (MD), and Esterman scores were recorded. Visual Activities Questionnaire (VAQ-33) and Visual Function Questionnaire (VFQ-25) questionnaires were administered.

RESULTS

Twenty patients with hemianopia and 22 healthy controls were included. The Esterman score in homonymous hemianopia patients (n = 17) correlated with best eye MD (r = -0.62, P = 0.01), worst eye MD (r = -0.70, P = 0.002), and average MD (r = -0.68, P = 0.003). Compared with healthy control subjects, patients with homonymous hemianopia had significantly lower VFQ-25 score and in 10/12 subscales (all P < 0.001). VAQ-33 scores revealed lower overall and subscales scores with the exception of light/dark adaptation (P = 0.08). Correlations were found between monocular and binocular VF scores and general vision (r = -0.55), peripheral vision (on both questionnaires, r-range -0.75 to 0.47), VFQ-25 and VAQ-33 overall scores (r = -0.59, -0.49 and 0.50), and glare disability (r = 0.53 and 0.67).

CONCLUSIONS

Hemianopic VF defects involve a major alteration in the patients' vision-related QoL.

When You Do Not Get the Whole Picture: Scene Perception After Occipital Cortex Lesions

Background: Occipital cortex lesions (OCLs) typically result in visual field defects (VFDs) contralateral to the damage. VFDs are usually mapped with perimetry involving the detection of point targets. This, however, ignores the important role of integration of visual information across locations in many tasks of everyday life. Here, we ask whether standard perimetry can fully characterize the consequences of OCLs. We compare performance on a rapid scene discrimination task of OCL participants and healthy observers with simulated VFDs. While the healthy observers will only suffer the loss of part of the visual scene, the damage in the OCL participants may further compromise global visual processing. Methods: VFDs were mapped with Humphrey perimetry, and participants performed two rapid scene discrimination tasks. In healthy participants, the VFDs were simulated with hemi- and quadrant occlusions. Additionally, the GIST model, a computational model of scene recognition, was used to make individual predictions based on the VFDs. Results: The GIST model was able to predict the performance of controls regarding the effects of the local occlusion. Using the individual predictions of the GIST model, we can determine that the variability between the OCL participants is much larger than the extent of the VFD could account for. The OCL participants can further be categorized as performing worse, the same, or better as their VFD would predict. Conclusions: While in healthy observers the extent of the simulated occlusion accounts for their performance loss, the OCL participants' performance is not fully determined by the extent or shape of their VFD as measured with Humphrey perimetry. While some OCL participants are indeed only limited by the local occlusion of the scene, for others, the lesions compromised the visual network in a more global and disruptive way. Yet one outperformed a healthy observer, suggesting a possible adaptation to the VFD. Preliminary analysis of neuroimaging data suggests that damage to the lateral geniculate nucleus and corpus callosum might be associated with the larger disruption of rapid scene discrimination. We believe our approach offers a useful behavioral tool for investigating why similar VFDs can produce widely differing limitations in everyday life.

Influence of Vision on Drivers: A Pilot Study

Background: Driving is the main mode of transportation in many countries, and visual safety depends largely on good visual health. The objective of this study is to analyze the visual health of Spanish drivers; as well as analyze the difference between professional and non-professional drivers. Methods: A visual screening was carried out in Spanish drivers from all over Spain, in which the following tests were performed: monocular visual acuity in distance and near vision, visual field, stereopsis, contrast sensitivity, intraocular pressure and balance test binocular. Subsequently, a questionnaire was carried out on the patient’s driving data and ocular antecedents. Results: 74.5% of the drivers used glasses to drive, of which 61.5% used progressive glasses. However, 39.4% reported having difficulties seeing well. The mean visual acuity in the distance and near was 0.93 ± 0.13 and 0.94 ± 0.13, respectively. Significant differences have been found in accident risk based on visual acuity (p < 0.001). But no significant differences have been found in terms of visual field, stereopsis, contrast sensitivity, binocular balance and intraocular pressure (p > 0.05). Conclusion: Vision appears to play a key role in driving and a good visual assessment is recommended for early detection of visual problems that may affect road safety. A study with a larger sample size would be necessary to confirm the results of this pilot study.

Driving with hemianopia VIII: Effects of a vibro-tactile assistance system on safety and gaze behavior in pedestrian crossing situations

People with homonymous visual field defects (HVFDs), the loss of vision in the same half of the visual field in both eyes, are permitted to drive in some jurisdictions. However, the HVFD may cause difficulties in detecting hazards approaching on the side of the field loss (the blind side). An advanced driver assistance system (ADAS) could assist with hazard detection, but little research has been conducted to evaluate the potential benefits of an ADAS for visually impaired drivers. We developed a prototype vibro-tactile assistance system for drivers with HVFDs and conducted a proof-of-concept driving simulation study to evaluate the system. Given that pedestrian accidents are the second most frequent cause of death in road traffic and most of those accidents occur in urban scenarios, we evaluated the potential of the assistance system to improve responses to pedestrian hazards in a city environment. Sixteen participants, of which eight had HVFDs and eight had normal vision, took part. Our analyses evaluated the effects of the driver assistance system, crossing direction and pedestrian behavior on the safety of pedestrian events and the participant's gaze behavior at each of the 256 crossing situations. Generalized linear mixed effects models were used to assess binomial outcome variables. Despite the limited sample size, the results suggest that the vibro-tactile directional warnings were effective in directing the drivers' gaze so that they were looking in the necessary direction before a potential hazard occurred. More time was spent fixating pedestrians on the blind side when the ADAS was engaged and as a result, the safety of street crossings from the blind side improved. The effect of the ADAS was greater on responses to pedestrians from the blind than the seeing side. With an activated ADAS, crossings from the participants' blind sides were as safe as from their seeing sides, and as safe as the crossings when normally-sighted participants were driving. The results suggest that the vibro-tactile ADAS is a promising approach to improve the safety of drivers with HVFD and surrounding traffic.

Prognostic Factors for Long-Term Recovery of Homonymous Visual Field Defects After Posterior Circulation Ischemic Stroke

OBJECTIVES

Ischemic stroke (IS) is the main cause of homonymous visual field defects (HVFDs) in adults. Some reports suggest recovery even in late-phase strokes, but data is sparse. This study examines the frequency of long-term recovery from HVFDs in patients with posterior circulation infarction (POCI) and evaluates whether demographic or clinical characteristics are prognostic factors of perimetric recovery.

MATERIALS AND METHODS

Our study included patients with HVFDS due to POCI who had undergone 2 or more kinetic perimetric evaluations at least 6 months after the index IS. Clinical and imaging data were systematically reviewed and we performed univariate and multivariate logistic regression analyses to determine whether demographic, stroke etiology (TOAST classification), and initial perimetric patterns were prognostic factors of visual recovery occurring 6 months and beyond from POCI.

RESULTS

One hundred one patients with POCI were included. Median subject age was 60 years and 54.4% were female. After a median perimetric follow-up time of 13.5 months, spontaneous visual improvement was observed in 15.8% of patients. Prognostic factors for visual improvement were age < 50 years (OR 4.6; P = 0.093), POCI associated with hypercoagulable states (OR 12.3; P = 0.048), and vertebral artery dissection (OR 12.6; P = 0.048), while the presence of complete homonymous hemianopia was a negative predictor of recovery (OR 0.2; P = 0.048).

CONCLUSION

Partial visual recovery in HVFDs is observed even 6 months and beyond POCI. Age < 50 years and stroke etiology were predictors of recovery.

Motor Vehicle Accident Due to Homonymous Hemianopia: An Unusual Presentation of Vertebrobasilar Stroke

Acute ischemic stroke may present with various symptoms, including weakness, altered speech, and sensory and visual impairment. We present a case of a 57-year-old man who was brought to the emergency department after he sustained three minor motor vehicle accidents on the same day. After clinical assessment and detailed workup, we concluded that our patient had an acute ischemic infarct involving the left posterior cerebral artery territories causing right homonymous hemianopia resulting in motor vehicle accidents.

Driving With Hemianopia VII: Predicting Hazard Detection With Gaze and Head Scan Magnitude

Purpose

One rehabilitation strategy taught to individuals with hemianopic field loss (HFL) is to make a large blind side scan to quickly identify hazards. However, it is not clear what the minimum threshold is for how large the scan should be. Using driving simulation, we evaluated thresholds (criteria) for gaze and head scan magnitudes that best predict detection safety.

Methods

Seventeen participants with complete HFL and 15 with normal vision (NV) drove through 4 routes in a virtual city while their eyes and head were tracked. Participants pressed the horn as soon as they detected a motorcycle (10 per drive) that appeared 54 degrees eccentricity on cross-streets and approached toward the driver.

Results

Those with HFL detected fewer motorcycles than those with NV and had worse detection on the blind side than the seeing side. On the blind side, both safe detections and early detections (detections before the hazard entered the intersection) could be predicted with both gaze (safe 18.5 degrees and early 33.8 degrees) and head (safe 19.3 degrees and early 27 degrees) scans. However, on the seeing side, only early detections could be classified with gaze (25.3 degrees) and head (9.0 degrees).

Conclusions

Both head and gaze scan magnitude were significant predictors of detection on the blind side, but less predictive on the seeing side, which was likely driven by the ability to use peripheral vision. Interestingly, head scans were as predictive as gaze scans.

Translational Relevance

The minimum scan magnitude could be a useful criterion for scanning training or for developing assistive technologies to improve scanning.

Comparing Component-Based and Occupation-Based Interventions of a Person with Visual Deficits' Performance

This study aimed to compare the effectiveness of component-based, occupation-based, and a combined intervention for visual-scanning to improve occupational performance. This exploratory case study used a 55-year-old female, seven years post-stroke with visual field deficits, who completed a component-based intervention (Vision Coach), an occupation-based intervention (IADL activities that incorporated scanning tasks), and a combined intervention. The Assessment of Motor and Process Skills (AMPS) was completed prior to and after each intervention. Participant's data was compared between interventions and AMPS standardization sample, with observable improvements in motor skills and process skills. Visual-scanning training as a compensatory method appears to be effective for chronic visual field deficits post-stroke, particularly using component-based and occupation-based interventions in combination.

2017 Charles F. Prentice Award Lecture: Peripheral Prisms for Visual Field Expansion: A Translational Journey

On the occasion of being awarded the Prentice Medal, I was asked to summarize my translational journey. Here I describe the process of becoming a low-vision rehabilitation clinician and researcher, frustrated by the unavailability of effective treatments for some conditions. This led to decades of working to understand patients' needs and the complexities and subtleties of their visual systems and conditions. It was followed by many iterations of developing vision aids and the techniques needed to objectively evaluate their benefit. I specifically address one path: the invention and development of peripheral prisms to expand the visual fields of patients with homonymous hemianopia, leading to our latest multiperiscopic prism (mirror-based design) with its clear 45° field-of-view image shift.

Useful Field of View Performance in the Intact Visual Field of Hemianopia Patients

Purpose

Postchiasmatic brain damage commonly results in an area of reduced visual sensitivity or blindness in the contralesional hemifield. Previous studies have shown that the ipsilesional visual field can be impaired too. Here, we examine whether assessing visual functioning of the “intact” ipsilesional visual field can be useful to understand difficulties experienced by patients with visual field defects.

Methods

We compared the performance of 14 patients on a customized version of the useful field of view test that presents stimuli in both hemifields but only assesses functioning of their intact visual half-field (iUFOV) with that of equivalent hemifield assessments in 17 age-matched healthy control participants. In addition, we mapped visual field sensitivity with the Humphrey Field Analyzer. Last, we used an adapted version of the National Eye Institute Visual Quality of Life-25 to measure their experienced visual quality of life.

Results

We found that patients performed worse on the second and third iUFOV subtests, but not on the first subtest. Furthermore, patients scored significantly worse on almost every subscale, except ocular pain. Summed iUFOV scores (assessing the intact hemifield only) and Humphrey field analyzer scores (assessing both hemifields combined) showed almost similar correlations with the subscale scores of the adapted National Eye Institute Visual Quality of Life-25.

Conclusions

The iUFOV test is sensitive to deficits in the visual field that are not picked up by traditional perimetry. We therefore believe this task is of interest for patients with postchiasmatic brain lesions and should be investigated further.

Buckle up!

Die Verkehrsmedizin als Teil der Rechtsmedizin erfüllt in der Schweiz eine wichtige präventive Aufgabe in der Sicherung aller Verkehrsteilnehmer: Sie begutachtet die medizinisch basierte Fahrfähigkeit und Fahreignung. Als empirisch konsolidiertes Querschnittsfach hat sie Informationen aus einer Vielzahl von medizinischen Fachgebieten. Wie reagiert die Verkehrsmedizin aber auf den vermehrten Anspruch evidenzbasierter Gutachten und auf anstehende Herausforderungen?

Über einen historischen Abriss motivierten wir die Vorteile und das Potential einer teilweise durch Fahrsimulation ergänzten Untersuchung und einer dediziert auf Fahrsimulation basierenden, klinisch-prospektiven Forschung.

Neben vorhandener Literatur stützen sich historische Aspekte u.a. auf vorhandene Expertise. Die Bewertung der Fahrsimulation für die Verkehrs- bzw. Rechtsmedizin der Schweiz stützt sich auf die Diskussion selektierter Literatur.

Auftrag und Anspruch der Verkehrsmedizin haben sich mehrfach verändert. Eine übersichtsartige Betrachtung existenter Literatur legt nahe, dass massgeschneiderte Fahrsimulatoren Teil einer modernisierten Verkehrsmedizin sein können, um anstehende Herausforderungen adäquat adressieren zu können. Bisher existiert kein derartiges dediziertes Forschungsinstrument in der Schweiz.

Eine auf verkehrsmedizinische Fragestellungen massgeschneiderte, realitätsnahe und niedrigschwellige Fahrsimulation als Werkzeug für klinische Studien und Individualuntersuchungen verspricht neben einer wissenschaftlichen Produktivität einen umsetzbaren und vermittelbaren Mehrwert für das übergeordnete Ziel der Sicherheit aller Verkehrsteilnehmer.

Multi-periscopic prism device for field expansion

Patients with visual field loss frequently collide with other pedestrians, with the highest risk being from pedestrians at a bearing angle of 45°. Current prismatic field expansion devices (≈30°) cannot cover pedestrians posing the highest risk and are limited by poor image quality and restricted eye scanning range (<5°). A new field expansion device: multi-periscopic prism (MPP); comprising a cascade of half-penta prisms provides wider shifting power (45°) with dramatically better image quality and wider eye scanning range (15°) is presented. Spectacles-mounted MPPs were implemented using 3D printing. The efficacy of the MPP is demonstrated using perimetry, photographic depiction, and analyses of the collision risk covered by the devices.

The determinants of motorized mobility scooter driving ability after a stroke

Purpose: To investigate the determinants related to the ability to drive a motorized mobility scooter after a stroke.Method: The study was a cross-sectional study. The ability to drive a motorized mobility scooter was measured with the Power Mobility Clinical Driving Assessment. The independent variables included cognitive functions measured by the Color Trails Test and reaction time test, visual functions measured by a visual acuity test and visual field test, and motor functions measured with a dynamometer, the Box and Block Test, and the Functional Independence Measure.Results: The correlation analyses revealed that the Power Mobility Clinical Driving Assessment scores had significant correlations with reaction time (ρ = -.65, p < 0.01), binocular visual field (r = .64, p < 0.01), binocular visual acuity (r = .40, p = 0.03), and the grip strength of the unaffected hand (r = .47, p = 0.01). The multiple regression analysis indicated that reaction time, binocular visual field, and the grip strength of the unaffected hand were the most significant determinants of the ability to drive a motorized mobility scooter (R² = .76).Conclusions: The reaction time, binocular visual field, and grip strength of the unaffected hand were the most significant determinants related to the ability to drive a motorized mobility scooter after a stroke. IMPLICATIONS FOR REHABILITATIONMotorized mobility scooter driving ability for stroke patients is correlated with demographics (age, mobility scooter driving experience, time since last drive) and cognitive, visual and motor functions (reaction time, binocular visual field, visual acuity, and the grip strength of unaffected hand).Primary determinants of motorized mobility scooter driving ability for stroke patients include reaction time, binocular visual field, and grip strength of the unaffected hand.Comprehensive assessments incorporating cognitive, visual and motor functions are needed to evaluate the ability to drive a motorized mobility scooter after a stroke.

Is simulator-based driver rehabilitation missing motion feedback?

Currently, driver rehabilitation involves use of fixed-base simulators. Such simulators are used infrequently and with little success. We hypothesize that the absence of motion feedback may be limiting the therapeutic effectiveness of driving simulation. During real, motor vehicle driving, the driver receives motion feedback that provides rich and real-time information about acceleration, deceleration and turning of the vehicle. Thus, motion feedback may be a key missing component that could dramatically increase the clinical pragmatism of simulator-based driver rehabilitation. In this pilot study, six young adult drivers participated in simulated driving tasks with or without motion feedback. Participants who received motion feedback completed faster laps on a racetrack and committed fewer driving infractions on a highway. They reported being more motivated and aware of the pressure of high speed driving. Particularly, they experienced substantially fewer symptoms of simulator sickness, a primary impedient to widespread use of driving simulators for driver rehabilitation. These preliminary finding motivate a full investigation of the impacts of motion feedback during simulated driving, and of the efficacy of lower cost, two degree of freedom driving simulators for clinical use.

Driving With Hemianopia VI: Peripheral Prisms and Perceptual-Motor Training Improve Detection in a Driving Simulator

Purpose

Drivers with homonymous hemianopia (HH) were previously found to have impaired detection of blind-side hazards, yet in many jurisdictions they may obtain a license. We evaluated whether oblique 57Δ peripheral prisms (p-prisms) and perceptual-motor training improved blind-side detection rates.

Methods

Patients with HH (n = 11) wore p-prisms for 2 weeks and then received perceptual-motor training (six visits) detecting and touching stimuli in the prism-expanded vision. In a driving simulator, patients drove and pressed the horn upon detection of pedestrians who ran toward the roadway (26 from each side): (1) without p-prisms at baseline; (2) with p-prisms after 2 weeks acclimation but before training; (3) with p-prisms after training; and (4) 3 months later.

Results

P-prisms improved blind-side detection from 42% to 56%, which further improved after training to 72% (all P < 0.001). Blind-side timely responses (adequate time to have stopped) improved from 31% without to 44% with p-prisms (P < 0.001) and further improved with training to 55% (P = 0.02). At the 3-month follow-up, improvements from training were maintained for detection (65%; P = 0.02) but not timely responses (P = 0.725). There was wide between-subject variability in baseline detection performance and response to p-prisms. There were no negative effects of p-prisms on vehicle control or seeing-side performance.

Conclusions

P-prisms improved detection with no negative effects, and training may provide additional benefit.

Translational Relevance

In jurisdictions where people with HH are legally driving, these data aid in clinical decision making by providing evidence that p-prisms improve performance without negative effects.

Driving with Hemianopia V: Do Individuals with Hemianopia Spontaneously Adapt Their Gaze Scanning to Differing Hazard Detection Demands?

Purpose

We investigated whether people with homonymous hemianopia (HH) were able to spontaneously (without training or instructions) adapt their blind-side scan magnitudes in response to differing scanning requirements for detection of pedestrians in a driving simulator when differing cues about pedestrian eccentricities and movement behaviors were available in the seeing hemifield.

Methods

Twelve HH participants completed two sessions in a driving simulator pressing the horn when they detected a pedestrian. Stationary pedestrians outside the driving lane were presented in one session and approaching pedestrians on a collision course in the other. Gaze data were analyzed for pedestrians initially appearing at approximately 14° in the blind hemifield. No instructions were given regarding scanning.

Results

After appearing, the stationary pedestrians' eccentricity increased rapidly to a median of 31° after 2.5 seconds, requiring increasingly larger blind-side gaze scans for detection, while the approaching pedestrians' eccentricity remained constant at approximately 14°, requiring a more moderate scan (∼14°) for detection. Although median scan magnitudes did not differ between the two conditions (approaching: 14° [IQR 9°–15°]; stationary: 13° [IQR 9°–20°]; P = 0.43), three participants showed evidence of adapting (increasing) their blind-side scan magnitudes in the stationary condition.

Conclusions

Three participants (25%) appeared to be able to apply voluntary cognitive control to modify their blind-side gaze scanning in response to the differing scanning requirements of the two conditions without explicit training.

Translational Relevance

Our results suggest that only a minority of people with hemianopia are likely to be able to spontaneously adapt their blind-side scanning in response to rapidly changing and unpredictable situations in on-road driving.