10-03-05
Open Your Eyes to Driving
Farrell S. F. Sheffield
Summary
Visual impairments may occur so slowly over time that drivers aren't aware of them. Occupational therapy practitioners can identify and interpret the functional implications of low-vision conditions, and teach drivers to use compensatory techniques.
"Vision is 90% of the information required for driving" (p. 224).1 We make decisions based on what we see. Loss of vision due to aging can be gradual and undetected by a driver if he or she does not undergo regular screenings by an eye professional. Low vision is defined as visual loss that cannot be corrected by lenses and results in disability with daily activities.2 This loss of vision may be the result of disease or simply changes related to aging, but in all cases may result in driver error. For example, glaucoma, diabetes, macular degeneration, and cataracts can affect visual acuity, depth perception, visual search, and visual field. Vision deficits combined with restricted head movements, which also may occur with aging, can delay processing of critical information and combine to affect driving even more.
Changes in vision can have less obvious effects as well. Visual attention is an important aspect of the cognitive skills of divided, selective, and sustained attention. Visual attention is especially important with respect to driver safety. The older driver may take longer to react to and process sensory information. If sensory processing is delayed, hazards on the road can be overlooked, and important information in the environment can be misinterpreted. A driver may not see a pedestrian, or may misread or miss a road sign. Low-light conditions or glare can make it difficult for seniors to identify objects and read signs. Clearly, the gradual nature of many visual changes, combined with the dangers of driving with low vision, point to the necessity of regular eye exams and to the need for compensatory strategies for drivers. The following are common areas of concern among drivers with low vision.
Visual Acuity and Visual Field
Visual acuity, or the ability to see objects distinctly in the central field (straight ahead), is important for reading signs and avoiding hazards.1 Judging oncoming traffic requires using central vision to make decisions about speed and distance.3 Acuity is depressed at sunset and sunrise due to changing illumination (e.g., a driver may not notice a black car at night as easily as during the daytime), so persons with decreased acuity should not drive during these times. Decina and Staplin have inferred that results from visual screening of acuity, fields, and contrast sensitivity is strongly related to crash rates in older drivers.4 With proper training, occupational therapists can assess these visual skills through standardized protocols and tests.
In addition to central field visual skills, a driver depends on peripheral field awareness (seeing objects approaching from the side). The peripheral field allows for movement detection, providing advance warning of objects. Scanning visual fields is essential when controlling a vehicle. A collapsed visual field, exemplified by decreased peripheral or attentional fields, can manifest in its most severe form as "tunnel vision."5 With this condition, eye movements are limited to the central 20°, with a resulting tendency to move one's head (rather than the eyes) to fixate on and follow a visual target. Because driving at night also reduces peripheral field function, even with headlight use, drivers with reduced visual fields should drive only during the day.
Cataracts can distort perception of objects and reduce contrast detection, which is important for judging distance and detecting hazards. Reduced illumination or low-light driving conditions (such as at dawn and dusk) can further reduce the visual information that is critical for driver decisions.
Visual acuity and visual field requirements to drive vary from state to state. See the Physician's Guide to Assessing and Counseling Older Drivers6 online for state Department of Motor Vehicle licensing requirements, including state visual guidelines.
Useful Field of View
The useful field of view (UFOV) is defined as the area where one can take a quick glance to extract visual information without head or eye movement.7 Problems resulting from a reduced UFOV include slowed reaction time, decreased visual attention, and problems processing "visual clutter."8 In other words, a busy and complex visual environment may be confusing to a driver, with hazards overlooked. Many older drivers have increasing difficulty moving their heads quickly or twisting their trunk to improve line of sight and detect hazards, which reduces their UFOV. Cognitive impairment can also reduce UFOV by reducing the area that a driver can visually attend to, thereby increasing risk of a crash.
After a stroke, some persons experience visual field loss called hemianopsia, which may affect one or both eyes, as well as the upper and lower quadrants of the visual field. Someone with this type of visual loss has a smaller UFOV and is unable to see objects in the area of deficit, typically to the extreme right or left, but sometimes also toward the ground or sky. Some states allow driving with hemianopsia if the driver demonstrates the ability to compensate for field loss with adequate scanning, head turning, and anticipation.
An eye professional (optometrist or ophthalmologist) may prescribe prism or special lenses to help compensate for a visual field loss, shift images to where they can be seen, or address problems with eye alignment or depth perception. Although there is a lack of formal research in the use of prisms for driving, they have been used in the clinic to increase client awareness of the impaired visual field. Not all clients are candidates for prisms, however, because when an image is shifted by a prism, the result could be disorienting to the user. Some states allow intermittent spotting with bioptic telescopes mounted on glasses, which improves distance acuity but requires considerable training to use efficiently. Other visual field compensations include panoramic and specialty mirrors, visors, tinted lenses, and keeping vehicle windows clean for optimal viewing.
Glare
Glare, and delayed glare reaction, can be a problem for all drivers. Reflections from objects and the road can be temporarily blinding, and direct glare from the sun or headlights can cause a delay in seeing another vehicle, obstacle, or pedestrian. Older drivers may have the additional challenge of delayed glare recovery, which is often an early sign of glaucoma (which can be detected early and treated through regular eye exams). The effects of glare can be reduced by using tinted lenses prescribed by an optometrist or ophthalmologist, and by not driving at dusk or dawn or at night.
Depth Perception
Depth perception, or stereopsis, is the ability to see the relative distance of objects. Changes with aging, such as a cataract in one eye, may decrease binocular vision. Depth perception is important for judging distances between objects, such as when braking. If one's eyes are not "teaming" properly, then other cues such as shading and size can provide information on relative distances. Clients should be advised that driving at higher speeds can make it more difficult to judge distances and to safely enter the flow of traffic.
Visual Search
Efficient visual search is another important skill, whether walking across the street or deciding when to make a left turn as a driver. Changes after brain injury or with aging may affect fast and slow eye movements, resulting in disorganized scanning, or overshooting or undershooting an object. Occupational therapists can teach clients strategies to compensate for overscanning (e.g., looking from top to bottom and left to right) and to develop organized and efficient scanning patterns (e.g., getting into the habit of rescanning to be sure nothing is missed). Mastering relevant techniques will aid in such driving tasks as finding a parking space.
Professional Roles
The occupational therapist generalist can assess a client with basic visual deficits, and recommend remediation or compensation strategies to improve occupational performance, including providing guidance to help a client compensate for visual loss and enhance safety awareness. The occupational therapy assistant, with proper supervision and training, can also contribute to these activities. The evaluating therapist should observe the client in the community before determining appropriate interventions because clinic behavior may not match community functioning. For example, simulating driving in a parked car will yield some information about a driver, but it does not fully predict performance in a dynamic driving situation on the road.
In any case, a close working relationship between occupational therapy and either an ophthalmologist or optometrist benefits the client's daily function. An excellent model of this working relationship can be found in Understanding and Managing Vision Deficits: A Guide for Occupational Therapists, by Dr. Mitchell Scheiman.9 Developing relationships with ophthalmologists and optometrists is important to expanding the practice of occupational therapy in low-vision rehabilitation. Promoting the unique role of occupational therapy can be done through activities such as providing an in-service at a meeting of ophthalmologists or optometrists. This type of education can lead to mutual understanding of how services can complement, not duplicate, efforts. Presenting occupational therapy case studies can be convincing, leading to referrals for vision loss compensation intervention.
Collaboration with an ophthalmologist or optometrist can increase one's understanding of eye disease, eye health, vision exams and measurements, and lenses and other devices. An optometrist may provide exams and lenses and manage disorders of the visual system, including assessing fixation and binocular skills. An optometrist with a neuro-optometric specialty, also known as a developmental or behavioral optometrist, has specialized training to address visual processing with movement and function.
Beyond Driving
Sometimes a client with visual impairment cannot compensate enough to continue driving. The occupational therapist can be instrumental in pulling together resources for clients and other health professionals, becoming the "go-to" authority in community mobility resources. A good way to get started is to compile a list of alternate transportation and community services for clients with visual impairment and update it regularly. It is also helpful to establish a rapport with case managers or hospital discharge planners by letting them know what services you can offer relative to driving and community mobility. Educating senior groups, instructors of senior driver safety classes like AARP's Older Driver Safety Course, and area physicians creates an information network. If an older driver identifies an occupational therapist as a driver advocate early on, the advocate can help the driver determine how to keep driving for as long as possible, and prepare resources for when that is no longer possible. The relationships among the occupational therapist, occupational therapy assistant, and local eye professionals are critical to meet client needs relative to low vision and driving.
References
1. Higgins, K. E., & Tait, A. (1998). Vision and driving: Selective effect of optical blur on different driving tasks. Human Factors, 41(2), 224-232.
2. Peli, E., & Peli, D. (2002). Driving with confidence: A practical guide to driving with low vision. London: World Scientific.
3. Isler, R. B., Parsonson, B. S., & Hansson, G. J. (1997). Age related effects of restricted head movements on the useful field of view of drivers. Accident Analysis and Prevention, 29, 793-801.
4. Decina, L. E., & Staplin, L. (1993). Retrospective evaluation of alternative vision screening criteria for older and younger drivers. Accident Analysis and Prevention, 25, 267-275.
5. Larroquette, I., & Berthiaume, J. (2005, February). Costly condition. Advance for Directors in Rehabilitation, 63-65.
6. American Medical Association. (2003). State licensing requirements and reporting laws. In Physician's guide to assessing and counseling older drivers (pp. 76-146). Chicago: Author. Retrieved July 29, 2005, from http://www.ama-assn.org/ama1/pub/upload/mm/433/chapter8.pdf
7. Visual Awareness. (n.d.). What is UFOV? Retrieved July 9, 2005, from http://www.visual awareness.com/Pages/whatis.html
8. Higgins, K. E., & Bailey, I. L. (2000). Visual disorders and performance of specific tasks requiring vision. Vision Impairment, 1, 287-315.
9. Scheiman, M. (2002). Understanding and managing vision deficits: A guide for occupational therapists (2nd ed.). Thorofare, NJ: Slack.
Farrell S. F. Sheffield, OTR/L, HTC, CDRS, is an occupational therapist, certified as a driving rehabilitation specialist, with advanced practice in hand therapy. She has been a clinician for more than 25 years in hospital, outpatient, and home health settings, working with children and adults with physical disabilities. She is a member of the Neuro- Optometric Rehabilitation Association, and the founder and coordinator of Tri-City Medical Center's "Good to Go" Driving Rehabilitation program in San Diego County. She received driving instructor training in 2002 from the California Driving School Inc. and was the 2004 AOTA Driver/Driving Network Coordinator.
A special acknowledgment to Susan Daniel, OD, Timothy Holmes, OTR/L, BCN, Janet Berthiaume, OTR, Laura Nelson, MA, OTR/L, and Maryfrances Gross, COTA, CDRS, for their support as consultants for this article.
Clinical Application
Q: A client identified as having mild cognitive impairment and early dementia requests a road test only, with no clinic assessment. She has not seen an eye professional to evaluate her glasses prescription in a few years. Should the occupational therapist fulfill her request?
A: In most cases, a clinic evaluation is important to identify any problem areas before the road test. This evaluation helps the driver specialist focus on those areas and to modify the driving demands, if appropriate. A road test would then be conducted in a more informed manner. However, the most important factor in this and all cases is that the client may have visual changes that can affect safety on the road and that the occupational therapist is not qualified or licensed to detect. Recommend a vision evaluation by an eye professional, and explain the need for the clinic assessment as the next step with a road test to follow if appropriate. Physician support for this approach may positively influence the client's perspective.
For More Information
AOTA CE Workshop: Occupational Therapy and the Older Driver: Addressing the IADL of Community Mobility and Driving
Presented by Susan Pierce, Elin Schold Davis, and Carol J. Wheatley. Indianapolis, IN, October 21-22 (Order #DR1005-MI); Location TBA, February 24-25 (Order #DR206-MI). $355 for members, $495 for nonmembers. To register go to www.aota.org or call toll free 877-404-AOTA.
AOTA CE Workshop: Occupational Therapy Symposium on Driving and Community Mobility
Presented by Vanessa M. Dazio, Linda Hunt, Mary Ellen Keith, Elysa Roberts, Miriam Watson, and Barbara Winters. Orlando, FL, December 3-4 (Order #CM1205-MI). $355 for members, $495 for nonmembers. To register go to www.aota.org or call toll free 877-404-AOTA.
AOTA Online Resources:
Occupational Therapists and Driving Web site
www.aota.org/olderdriver/
Association of Driver Rehabilitation Specialists (ADED)
www.aded.net
How Much Visual Road Information Is Needed To Drive Safely and Comfortably?
By D. deWaard, F. J. J. M. Steyvers, & K. A. Brookhuis, 2004. Safety Science, 42, 639-655.
The Lighthouse Inc.
www.lighthouse.org/
National Highway Traffic Safety Administration (NHTSA)
www.nhtsa.dot.gov/
Neuro-Optometric Rehabilitation Association (NORA)
www.nora.cc/
PhysicianÕs Guide to Assessing and Counseling Older Drivers By the American Medical Association and the National Highway Traffic Safety Association
http://www.ama-assn.org/ama/pub/category/ 10791.html
Predicting Components of Closed Road Driving: Performance From Vision Tests
By K. E. Higgins & J. Wood (in press). Optometry and Vision Science.
Visual Attention and Driving Behaviors Among Community-Living Older Persons
By E. D. Richardson & R. A. Marottoli, 2003. Journal of Gerontology: Medical Sciences, 58, 832-836.
Reference Information:
Sheffield, F. S. F. (2005). Open your eyes to driving. [Electronic Version]. OT Practice, 10(18), 10-13.
©Copyright 2005. The American Occupational Therapy Association. All rights reserved.
