Driving Difficulties and Coping Strategies in Persons with Homonymous Quadrantanopia or Homonymous Scotoma

Abstract

Introduction:

This study, conducted in the United States, investigated the challenges faced by drivers with homonymous visual field loss and their coping strategies, including the use of in-vehicle Advanced Driver Assistance Systems (ADAS).

Methods:

Four current drivers with either homonymous quadrantanopia or homonymous scotoma caused by a stroke completed an in-depth semi-structured telephone interview. Using mostly open-ended questions, the interview addressed the difficulties encountered while driving, strategies used to cope with the difficulties, and the use of ADAS.

Results:

The main difficulties related to seeing objects on side of the field loss especially at intersections and when merging or changing lanes. Cases with left-sided field loss reported problems with left turns and seeing oncoming cars at intersections. Cases with homonymous scotomas described how cars disappeared in and out of the scotoma. Two cases reported many driving difficulties at first, but fewer difficulties as they became used to driving with the field loss. The most common coping strategies included scanning to the side of the field loss (including large scans with head movements), use of rearview/side mirrors, adding mirrors to the car, leaving more space on the side of the field loss, avoiding difficult driving situations and the use of ADAS (blind spot warning, GPS navigation and rearview camera).

Discussion:

All cases reported some difficulties consistent with those found in on-road and driving simulator studies of individuals with homonymous visual field loss. Over time they each reported developing a set of strategies, including use of ADAS, for coping with the field loss that enabled them to be active drivers with relatively few self-imposed restrictions.

Implications for Practitioners:

Advising drivers with stroke-related field loss about potential difficulties and compensatory strategies is an important part of preparation for return to driving. The paper provides examples of problem situations, coping strategies and ADAS use which can be used to guide discussion.

Homonymous visual field loss (HVFL) is a loss of vision on the same side of the visual field in both eyes caused by damage to the postchiasmal visual pathways. HVFL can range from homonymous scotomas (a scotoma or blind area respecting the vertical midline, surrounded by functional visual field; Figure 1) to homonymous quadranopia (the loss of one quadrant of the visual field; Figure 1), and homonymous hemianopia (the complete loss of one hemifield). There are relatively little data addressing the prevalence of HVFL in the general population in the United States. However, in a population-based survey of an urban community near Sydney, Australia, HVFLs were found to affect nearly 1% of people over 49 years of age (Gilhotra et al., 2002). Stroke is the most common cause of HVFL. In a review of 904 cases of HVFL, 70% resulted from stroke. Other common causes of HVFL include traumatic brain injury, brain tumors, and brain surgery (Zhang et al., 2006).

Figure 1. Binocular Visual Field Plots for Each Case.

Note: This figure demonstrates the binocular visual field plots (Goldman V4e) for each case. The grey shading indicates areas that are not seen. Case 1 – Inferior left homonymous scotoma. Case 2 – Left quadrantanopia with field loss extending into the upper quadrant. Case 3 – Lower right quadrantanopia with field loss extending into the upper quadrant. Case 4 – Upper left homonymous scotoma.

Driving is an important rehabilitation goal for many people with HVFL. In this study we focus on individuals with homonymous quadranopia or homonymous scotomas driving in the United States (driving on the right side) because they meet the minimum visual field requirements for driving in most states whereas individuals with homonymous hemianopia do not (Peli, 2002). An on-road study (in which participants drove a dual-brake car along a 14-mile route including city and interstate driving while researchers rated their performance from the back seat) reported that drivers with quadranopia who were rated as unsafe to drive tended to have difficulties with steadiness in steering, lane position, and gap judgement (Wood et al., 2009). In a simulator study, drivers with homonymous scotoma were found to have delayed responses in detecting and reacting to pedestrians that appeared within the scotomatous area (Bronstad et al., 2011). Despite such difficulties, at least 80% of individuals with quadranopia were rated as safe to drive by driving examiners in on-road evaluations of fitness to drive in Canada (Dow, 2022 (78%); Racette & Casson, 2005 (100%)), the Netherlands (80%; De Haan et al., 2014), and the United States (88%; Wood et al., 2009). These findings suggest that many of the drivers with quadranopia may have developed effective coping strategies to overcome driving difficulties resulting from their field loss.

Self-reports provided by drivers with visual impairment represent a valuable source of information for understanding their driving difficulties and coping strategies. However, only limited data from a questionnaire study by Parker et al. (2011) are available on self-reported difficulties of drivers with hemianopia and quadranopia. In that study, the data were reported for the two categories of field loss combined, which may have led to an oversight of driving difficulties specific to each group. To our knowledge, self-reported strategies used to cope with driving difficulties have not previously been studied for drivers with any kind of HVFL. Drivers with other types of vision loss (such as glaucoma or age-related macular degeneration) report avoiding difficult driving situations because of their vision loss (Bowers et al., 2016a; Ramulu et al., 2009). It is, therefore, possible that drivers with quadranopia or homonymous scotomas might modify their driving behaviors or driving patterns to avoid challenging driving situations such as left turns across traffic. Furthermore, results from on-road and driving simulator studies suggest that some drivers with HVFL might adopt compensatory driving behaviors such as scanning more toward the affected side (Bowers et al, 2014; Bowers, 2016b; Wood et al., 2011) or taking a lane position toward the seeing side to give them more of a safety margin on the side of the field loss (Bowers et al., 2010; Wood et al., 2011). However, there are no prior studies which have specifically asked drivers with quadranopia or homonymous scotomas to self-report compensatory driving behaviors.

Advanced Driver Assistance Systems (ADAS) integrate sensors, cameras, and other technologies in vehicles to monitor the surrounding environment, detect potential hazards, and provide warnings or automatic assistance to drivers in avoiding collisions or accidents. Some common ADAS features, such as Cruise Control, Blind Spot Warnings, Lane Departure Warnings, and Forward Collision Warnings, are widely available in newer vehicles. Many studies have demonstrated that these technologies could effectively mitigate crash risk and enhance driving safety for drivers with normal vision (Cicchino, 2017; Seaman et al., 2022; Wang et al., 2019). ADAS have great potential to support driving for drivers with vision impairments. Recent questionnaire studies investigating the use of ADAS by drivers with vision impairment have revealed the perceived benefits associated with these features, such as reduced self-imposed driving restrictions, decreased stress levels, and increased driving confidence (Cucuras et al., 2017; Deffler et al., 2021; Xu et al., 2022; 2023a; 2023b). However, these studies primarily focused on drivers with central vision loss and there is no knowledge about whether drivers with HVFL utilize these technologies and the potential benefits or challenges they may encounter.

During development of a questionnaire to address these knowledge gaps, we conducted in-depth interviews with four current drivers with homonymous quadranopia or homonymous scotoma. Through open-ended questions we captured the details of specific driving difficulties and coping strategies, as well as how they utilized ADAS technologies in their everyday driving. This paper summarizes the findings and may be helpful to vision rehabilitation professionals when discussing return to driving with patients with homonymous quadranopia or homonymous scotomas.

Methods

Participants

A convenience sample of four current drivers with a history of stroke resulting in homonymous quadranopia or homonymous scotoma were included in this study. They were recruited from a database of participants who had participated in prior studies at Schepens Eye Research Institute. They were selected to represent a range of experience in driving with HVFL and to include both left- and right-side field loss. All participants were resident in the United States and drove on the right side of the road.

Procedures

A semi-structured interview (45 to 60 minutes) was administered to each participant by telephone. The interview comprised three main sections: 1) Background information; 2) Driving difficulties and coping strategies in specific driving situations; 3) Use of ADAS in their current vehicle (Table 1). Questions were primarily in yes/no single choice format and open-ended question format for short answers. The background section included questions asking about their demographics, HVFL history and rehabilitation training history, driving history, current driving habits, and current vehicle. The driving difficulties and strategies section included seven subsections addressing situations that might be difficult for drivers with HVFL (Bowers, 2016b), such as maintaining lane position, merging or changing lanes, dealing with intersections (Table 1). Each subsection started with a general, open-ended question followed by a list of more specific situations. If a participant reported experiencing difficulties in a situation, they were asked to describe the specific difficulties encountered (open-ended question) as well as any coping strategies employed (open-ended question). Our goal was to obtain participants’ self-reports in their own words without any suggestions from the interviewer of potential difficulties or strategies. The ADAS section asked about eight systems that are currently available in vehicles (Table 1). For each ADAS feature, participants were read a description of the system and then asked whether their vehicle was equipped with it (Yes, No, Not sure). If yes, they were asked whether they used the system and whether it was helpful.

Table 1.

Summary of Interview Content

Section	Description
Background information	Demographics
	HVFL history and rehabilitation training history
	Driving history
	Current driving habits
	Current vehicle information
Driving difficulties and coping strategies	General driving situations (6 items)
	Maintaining lane position and lane keeping (9 items)
	Merging or changing lanes (6 items)
	Dealing with intersections (12 items)
	Seeing and responding to unexpected events (6 items)
	Finding and reading traffic signs (2 items)
	Parking (3 items)
Advanced Driver Assistance Systems (ADAS)	GPS navigation system
	Rear view camera
	Cruise control/Adaptive cruise control
	Lane departure warning/Lane keeping assist
	Blind spot warnings
	Forward collision warning/Avoidance system
	Pedestrian warning system
	Automatic parking

Two investigators were present during each interview. One investigator led the interview and recorded the responses. The second investigator also recorded answers but focused on taking detailed notes of the open-ended questions. After each interview, both investigators who attended the interview reviewed the records together and came up with a final version of responses. Open-ended responses for each participant were reviewed by all study team members, and broad response themes were identified and are summarized in the results.

The study was conducted in accordance with the tenets of the Declaration of Helsinki and was approved by the institutional review board at Mass General Brigham. All participants provided informed and voluntary consent before the interview commenced.

Results

All four participants were male. At the time of the study, they each had binocular visual acuity of at least 20/20 and no indication of spatial neglect (Schenkenberg line bisection (Schenkenberg et al., 1980) and Bells tests (Vanier et al., 1990)). They each acquired HVFL (either homonymous quadranopia or homonymous scotoma) following a stroke between the ages of 49 and 61 years (Table 2). They were first licensed to drive between the ages of 16 and 18 years and held drivers’ licenses without any state-imposed restrictions at the time of the study. They all drove in a range of road situations (including towns and cities, on rural roads and highways).

Table 2.

Summary of Participant Demographics and Background

Characteristic	Case 1	Case 2	Case 3	Case 4
Age, years	50	62	73	67
Gender	Male	Male	Male	Male
Cause of visual field loss	Stroke	Stroke	Stroke	Stroke
Age at time of stroke, years	49	58	60	56
Visual Acuity, logMAR (Snellen)	−0.17 (20/14)	0.03 (20/21)	0.01 (20/20)	−0.13 (20/15)
Miles driven per week	230	75	200	100
Driving rehabilitation history	Yes	Yes	No	No
Years driving with field loss	1	4	12	11

Case 1

Case 1 (50 years) had an inferior left homonymous scotoma (60° horizontal extent; Figure 1) following a stroke 12 months previously. He described the scotoma as a “hole” in his vision. He received scanning training for reading and activities of daily living, had received a behind-the-wheel driving evaluation and was given training in strategies to compensate for vision loss when driving. He had almost 12 months experience of driving with the scotoma. He currently drove 230 miles per week (7 days per week) and did not avoid difficult driving situations.

Case 1 reported difficulties when an object approached from the left and was partially or fully obscured by his scotoma, including other vehicles, pedestrians, and bicyclists, especially at busy intersections. He noted difficulties with his scotoma obscuring traffic in the oncoming lane when he was looking straight ahead, and in the oncoming lane and center of the intersection when he was looking to the right before making a left turn. He was very concerned about failing to see oncoming cars making left turns across his travel path. Other difficulties included not seeing cars from the left lane moving into the lane in front of him (especially in busy traffic), not seeing cars from the left before he merged or changed lane to the left, not seeing cars in the left side blind spot of his car, not seeing curbs on the left in parking garages, not being able to see small traffic signs on the left and low to the ground, and difficulties recognizing familiar locations in the early days following the stroke.

To address his difficulties, Case 1 described frequent scanning to the left, making large scans to the left with head movement at intersections, needing to “sweep” his vision across the oncoming traffic lane, checking several times on the left before entering an intersection and keeping his gaze to the left after entering an intersection. He commented on the need to look far enough to the left before merging or changing lane to the left (which required a much larger head turn than previously) and reported looking ahead to identify potential obstacles on the left of the road.

In addition to these compensatory scanning behaviors, Case 1 purchased a new vehicle (2022 Hyundai Kona) equipped with a range of ADAS. He found the following systems helpful: Blind Spot Warning (provides an auditory warning if he starts to change lane when a vehicle is in the left blind spot of his car), GPS (he does not need to look for signs), Rearview Camera (includes a feature that provides warnings of pedestrians and vehicles approaching from the left/right behind the car), Cruise Control (reduces fatigue on long highway journeys) and Forward Collision Warning/Avoidance (automatic braking had engaged on one occasion). However, he reported that lane departure warning was not helpful, and does not use it.

Case 2

Case 2 (62 years) had a lower left homonymous quadrantanopia (extending into the upper quadrant; Figure 1) following a stroke 4 years previously. He received scanning training for walking and driving, and training in how to adjust and use the blind spot mirrors on the car. He had driven with the quadrantanopia for almost 4 years and currently drove 75 miles per week.

He reported difficulties with cars or other objects on the left side that were not in a seeing area of his visual field, including difficulties seeing cars on the left at intersections and when entering rotaries, and difficulties seeing cars in the left side blind spot of his car when merging or changing lanes to the left. When making left turns, he was concerned about failing to see oncoming cars (e.g., running a red light). Additionally, he reported a tendency to veer to the right when driving on a straight road.

To mitigate these difficulties, Case 2 implemented several strategies, including scanning more to the left, installing additional blind spot mirrors on his car, frequently checking mirrors, minimizing distractions (no radio or phone use) while driving, driving in the rightward lane (when there were multiple lanes), keeping away from the left lane boundary, and finding an “easy” parking spot away from other cars. He also avoided driving in peak hour traffic, making unprotected left turns across oncoming traffic, rotaries, driving at night, and in adverse weather conditions. He reported sometimes turning right rather than left at a busy intersection with a stop or yield sign (and then finding another less busy left turn). In general, he reported being a very cautious driver.

He drove a 2011 Mercedes Class C and used GPS navigation so that he did not need to look for signs but did not use any other ADAS.

Case 3

Case 3 (73 years) had a lower right homonymous quadrantanopia (extending into the upper quadrant; Figure 1) following a stroke 12 years previously. He did not receive any scanning training or driving rehabilitation. He had driven with the quadrantanopia for almost 12 years. Currently he drove 200 miles per week and did not avoid difficult driving situations.

He did not report many current difficulties but recalled the challenges he faced when first driving after his stroke, including difficulties seeing cars and pedestrians from the right side at intersections and when merging or changing lanes to the right. He mentioned difficulties in seeing children on the right because they are short and would be obscured by his field loss. He reported an incident shortly after the stroke when he had hit something on the right side of his driveway which had made him very aware of his field loss. He had not had any additional car accidents since that time.

To compensate for his field loss, Case 3 reported turning his head to the right a lot and being very careful to check the right side. He reported installing an additional mirror on the hood of his car and angling the rearview mirror to provide a better view of cars coming from behind on the right side. Additionally, he noted leaving more space on the right by taking a lane position away from the right lane boundary.

He drove a Toyota Sienna (2015 or 2016) and found the Blind Spot Warning system very helpful for warning of cars in the right-side blind spot. He also noted making use of GPS (route directions and warns of traffic situations), rearview camera (helpful because “there are so many things to look at when backing up”) and cruise control.

Case 4

Case 4 (67 years) had an upper left homonymous scotoma (maximum horizontal diameter 40°; Figure 1) following a stroke 11 years previously. He did not receive any scanning or driving rehabilitation training. After the stroke he taught himself how to scan while cycling and mentioned learning from a couple of close calls when riding his bike. Cycling was a “bridge” that helped him build confidence and resume driving. He had driven with the quadrantanopia for about 10 years and currently drove 100 miles per week. He avoided peak hour traffic and high traffic roads for reasons that were not related to his vision loss.

He reported that when he was looking straight ahead and he forgot to tilt his head and gaze upwards, he had difficulties seeing cars and pedestrians on the left at intersections. Cars from the left could disappear into the blind area in his vision and then suddenly reappear, which he described as “startling”. He also reported problems with his scotoma obscuring traffic lights (he did not see a left turn signal to the left of a signal for going straight) and obscuring the road ahead when he looked down at the speedometer. He noted more difficulties in the first year of driving with the field loss than he has currently. His biggest concern in the early years was not seeing pedestrians on the left, causing him to avoid urban areas and busy parking lots where pedestrians could come from any direction.

To compensate for his field loss, Case 4 reported moving the scotoma up “in the air” by tilting his head and gaze upward and then scanning the road with the “good part” of his vision. When merging or changing lanes to the left he mentioned the importance of keeping his gaze up, using mirrors and turning his head far to the left. He reported being extra vigilant when driving, checking areas where pedestrians or cars might appear and being very careful to check for cars in the oncoming lane at intersections (because there was one incident where he did not see an oncoming car turning right across his path). He drove slowly when first resuming driving and avoided freeways and urban areas. He no longer avoids these areas, but still avoids unprotected left turns and driving in bad weather.

He drove a 2014 Toyota Venza and used GPS, rearview camera, and cruise control, but reported that these systems did not help compensate for his field loss. However, he did find a blind spot warning system helpful in compensating for his field loss when driving a family member’s car.

Discussion

The four cases were all active drivers with a regular driver’s license, first licensed to drive in their teenage years, currently driving at least 75 miles per week. Their experience of driving with HVFL ranged from 1 to 12 years. Cases 1 and 2 had received scanning training and driving rehabilitation whereas Cases 3 and 4 had not. (In the state where these four participants resided, driving rehabilitation was not mandatory for persons with homonymous quadranopia or scotoma before returning to driving following a stroke). All cases reported at least some difficulties consistent with those found in on-road and driving simulator studies of individuals with HVFL (Bronstad et al., 2011; Bowers, 2016b; Wood et al., 2009). Over time they each reported developing a set of strategies for coping with the field loss that enabled them to be active drivers with relatively few self-imposed restrictions. Cases 1 and 3 did not self-restrict their driving while Cases 2 and 4 did report avoiding some difficult driving situations because of their vision loss.

As expected, the main self-reported difficulties related to seeing objects on the side of the field loss, especially at intersections and when merging or changing lanes. Cases 1, 2 and 4 with left-sided field loss reported specific problems with left turns and seeing oncoming cars at intersections (which would be obscured by the field loss when looking straight ahead). Cases 1 and 4 with left homonymous scotomas both described how cars disappeared into and then suddenly reappeared out of the scotoma. This phenomenon was not reported by Cases 2 and 3 who each had complete quadranopia and no peripheral vision beyond the temporal edge of the field loss. Only Case 2 reported problems with lane position, specifically veering toward the seeing side.

Case 1 reported the greatest number of difficulties with the most detailed descriptions, which may have been because he had the least experience of driving with field loss (only 12 months). However, it is also possible that he tended to drive in more challenging situations or was just more aware of his difficulties. Cases 3 and 4, each with more than 10 years driving with field loss, reported many difficulties in the early years but fewer difficulties as they became used to driving with field loss. They both reported incidents soon after the onset of the field loss which made them more aware of their vision loss and how it could impair detection of potential hazards when driving.

All four cases described scanning to the side of the field loss, including large scans with head movements, as a strategy to address difficulties with seeing objects on that side, especially at intersections and when merging/changing lane. Interestingly, Case 4 with a scotoma in the upper field, was the only person to report using a strategy of moving the scotoma vertically (in his case upward) so that it did not impede his view of the road ahead and he could scan laterally using the seeing part of his field (below the scotoma in visual field space). In contrast, Cases 1, 2 and 3 with predominantly lower field loss did not report any strategies to move the field loss vertically further down (but might unconsciously have been doing so).

Other strategies reported by at least two of the cases included using of rearview/side mirrors (all cases) or adding extra mirrors to their cars (Cases 2 and 3), leaving more space on the side of the field loss (Cases 2 and 3), avoiding unprotected left turns (Cases 2 and 4) and avoiding driving in bad weather (Cases 2 and 4). Driving defensively, looking ahead for potential problems on the side of the field loss, and checking multiple times on the side of the field loss were also common themes in the narrative reports. Finally, all cases reported using at least one ADAS which helped with difficulties resulting from their vision loss and Case 1 had purposefully purchased a new car with a range of modern ADAS. Blind Spot Warning and GPS navigation were the two ADAS most commonly reported as being helpful, providing warning of cars in the blind spot on the side of the field loss and obviating the need to look for signs, respectively. A Rearview Camera was also reported to be helpful by Cases 1 and 3.

We acknowledge that this study only reports experiences from four male drivers with homonymous quadranopia or scotoma and might not generalize to other people with different genders, races, ages or with other durations or types of HVFL (e.g., homonymous hemianopia). Furthermore, drivers with HVFL from countries that drive on the left side of the road (e.g., UK, Australia) may have different experiences. Data on ADAS usage is limited to whatever ADAS were present on the participant’s own vehicle. Nevertheless, this study provides useful and detailed insights into how drivers with homonymous quadranopia or homonymous scotoma cope with their driving difficulties and how it may be possible for drivers with HVFL to use ADAS technologies to assist their driving.

Implications for vision rehabilitation professionals

From a driving rehabilitation perspective, the findings highlight the importance of ensuring that people with homonymous quadranopia and scotomas have a clear understanding of the potential problems the vision loss can cause when driving. The narrative reports provide specific examples of problem situations and coping strategies for drivers with left and right HVFL (when driving on the right) which can be used by vision rehabilitation professionals as a basis for discussion with patients with homonymous quadranopia and scotomas without spatial neglect before they return to driving. The data highlight how a “close call” incident soon after driving made two of the cases much more aware of their field loss. This suggests a need not only to discuss but also demonstrate the effects of the field loss, for example using a driving simulator, if available. Finally, the findings suggest that vision rehabilitation professionals should consider the potential of ADAS when discussing return to driving. The narrative reports provide examples of the ADAS that the four cases found most helpful which can be used as a guide for discussion.