American Academy of Ophthalmology
POLICY
STATEMENT
Index
0.
Vision Requirements for Driving Policy
1.
Background
2.
The components of safe driving include the following
3.
Evaluation
4.
Visual Acuity
5.
Peripheral vision
6.
Useful Field of View: Visual Attention
7.
Contrast sensitivity
8.
Glare
9.
Eye Movement Disorders
10.
Central scotomas
11.
Colour vision
12.
Recommendations
References
Vision Requirements for Driving
Policy
The American Academy of Ophthalmology recognizes the need to
promote road safety. It also recognizes that the responsibility for
credentialing drivers lies with the state departments of motor vehicles and
their advisory boards, but acknowledges that ophthalmologists are regularly
called upon to evaluate candidates for driving based on visual parameters. In
the absence of well-proven test criteria and predictors of unsafe driving
characteristics, ophthalmologists must continue to advise patients according to
the established rules of their individual states.
Ophthalmologists may be called upon to make recommendations to
licensing agencies for candidates who do not meet unrestricted license
requirements. These recommendations, which can involve on-the-road testing for
further evaluation, may also specify restrictions for licensure limiting driving
to certain conditions, destinations, areas, times of day, or equipment. The
Academy recommends establishing evidence-based driver assessment and training
programs to address performance deficiencies. These data will help determine
what tests to administer, to whom, how often, and how to score them and apply
them to licensure.
Background
The preservation of road safety is the prime consideration in
addressing vision requirements for driving. The importance of road safety
demands that the components of safe driving be understood, the criteria for
evaluating candidates be evidence based, and the tests used be valid predictors
of driving ability.
The components of safe driving
include the following
1.The motor ability to scan a rapidly changing environment.
2.The sensory ability to perceive information in this rapidly changing
environment. 3.The attentiveness to process multiple pieces of information.
4.The cognitive ability to judge this information in a timely fashion and to
make appropriate decisions. 5.The motor ability to execute these decisions in a
timely fashion.
The interaction of these factors is complex and cannot be
inferred from the evaluation of one component alone. For example, an applicant
with an excellent visual acuity and fair mobility but impaired cognition may be
unsafe, whereas one whose only impairment is moderate visual acuity may be safe.
Another applicant with a combination of moderately impaired visual acuity,
moderately prolonged reaction time, and moderately impaired motor ability may be
unsafe.
Research is under way to develop tests with proved sensitivity
and specificity to identify high-risk drivers, but more work is needed to
confirm the results and expand on current findings. This is necessary to insure
safety on the roads, to assure fairness in licensing, and to enable
ophthalmologists to provide reasonable guidance to patients and to licensing
agencies and their medical advisory boards. The literature suggests that the
standard tests currently used are not adequate predictors of at-fault crash
involvement (9,10), whereas previous at-fault crash involvement is a more
reliable predictor (2).
Evaluation
The following components of visual sensory ability should be
evaluated for possible inclusion in vision tests to assess an individual's
ability to drive safely:
Visual Acuity
The easiest parameter to test is visual acuity, and in many
states this is the only criterion applied when issuing a driver's license.
However, there are no consistent data confirming that visual acuity is a valid
predictor of driving ability and safety. In fact, current data indicate that
factors other than visual acuity are more accurate predictors of safe driving
(9) and that there is no basis for the requirement of 20/40 visual acuity,
currently the policy in many states.
Although most ophthalmologists agree that severe visual
impairments (20/200 or a 20-degree visual field) should preclude driving, there
is no consensus about drivers with moderate visual impairments. Studies
undertaken in some states have used monocular visual acuity up to and including
20/70 for an unrestricted license and up to and including 20/100 after
evaluation and a road test. Prior to final testing, applicants are offered
training to compensate for their limitations. Unless there are exceptional
circumstances, individuals with visual acuities of less than 20/100 are denied
licensure (13). Some states allow licensure for applicants with visual acuities
up to but not including 20/200 who can demonstrate their ability in a road test.
Glasses or contact lenses should be worn as needed to optimize
visual acuity. More than half of the states allow drivers to use BiOptic
telescopes mounted on glasses, through which they spot traffic lights and
highway signs. It has not yet been demonstrated whether the estimated 2,500
BiOptic drivers in the United States drive more safely with their telescopes
than they would without them (10). The ability to drive safely using BiOptic
telescopes should be demonstrated in a road test in all cases.
The impact of reduced visual acuity on driving safety may be
decreased by restricting travel to familiar surroundings, non-rush hour times,
and low speed areas; by avoiding adverse weather conditions like rain or snow,
and allowing sufficient travel time.
Peripheral Vision
There is evidence that peripheral vision plays an important
role in safe driving (16). Studies have used a variety of definitions of visual
field impairment, however, which has resulted in a lack of consensus on the
breadth of visual field necessary for safe driving. No data exist on the
effectiveness of compensating for a visual field deficit (10). A driver with a
restricted visual field but excellent scanning ability, for example, may be
safer than a driver with a full visual field but no neck rotation.
Testing the mid-periphery is recommended because diseases such
as glaucoma and retinitis pigmentosa can create large discontinuities in that
area. Approximately half of the states in the United States do not require
peripheral visual field testing and, although there is no consensus among those
that do as to the definition of acceptable visual field, screening tests
presently available in vision screeners should be used.
Individuals with some degree of peripheral
visual field loss
who are cognizant of the parameters of their visual field may master
compensatory scanning techniques sufficient to drive safely. Individuals with hemianopic visual fields who have mastered scanning techniques are permitted to
drive in some states, although no formal studies of safety in this group have
been carried out (5). For some peripheral visual field defects, enlarged side
and rear-view mirrors may be useful.
Useful Field of View: Visual
Attention
The useful field of view (UFOV) test has been developed to
access an individual's ability to process and react in a timely fashion to
multiple visual events occurring simultaneously. It defines the visual field
within which rapidly presented visual material can be used. The test includes
processing speed, selective attention, and divided attention. A reduction in the
UFOV has been associated with increased future crash involvement, whereas a
moderate reduction in visual acuity, contrast sensitivity, and visual field were
not (8).
Because the UFOV test relies on both visual sensory and
cognitive skills, it provides a more global measure of visual functional status
than either sensory or cognitive tests alone (2). It is a good predictor of
driving performance for patients with normal acuities but impaired cognition
(3), and it is better than chronological age for identifying drivers at risk for
crashes (2). In some states the UFOV is used experimentally, and elsewhere it is
combined with other screening tests and simulators and used informally for
driver education programs (4, 13). It has been shown that with a modest
investment in training time, UFOV reduction can be partially reversed and
maintained for at least one year, although the impact of this improvement on
driving has not been tested. In some areas such training is offered
experimentally (4, 12).
Contrast Sensitivity
Contrast sensitivity is not currently a licensing parameter in
any state, although a new study has associated severe reduction in contrast
sensitivity with increased crash risk (12). Drivers with reduced contrast
sensitivity may benefit by limiting their driving to the hours between dawn and
dusk, and some find their contrast sensitivity improved by wearing yellow
filters.
Glare
Glare has been discussed as a safety threat, but there are no
studies to date that support this contention (10). Some drivers find that glare
is reduced by wearing yellow filters and polarized lenses.
Eye Movement Disorders
It is known that experienced drivers continuously scan the
road to glean useful information, but there is no research on drivers with eye
movement disorders (10). Neck rotation, which may facilitate scanning and
compensate in part for eye movement disorders, is included in the vision testing
in some states (6)..
Central Scotomas
Individuals with central visual field defects who are
cognizant of the parameters of their defect may learn effective compensatory
scanning techniques. One study found that drivers with Stargardt's Disease and
cone-rod dystrophy affecting central vision had an increased crash risk only for
night driving when compared to controls (14). It may be advisable to limit these
individuals to daytime driving.
Color vision
Some states test color vision, anticipating that it is
important for identifying traffic signals accurately, but drivers with color
deficiencies successfully use clues other than color. Studies show no
association between color deficiency and reduced driving performance (10, 15),
and this component of visual sensory ability should not be included in vision
tests to access an individual's ability to drive safely.
Recommendations
Testing should include cognitive and motor abilities as well
as visual sensory ability. In general it is reasonable to consider performance
on screening tests in three basic ranges. If performance is excellent, driving
ability may be assumed to be normal unless the individual's driving record
suggests otherwise. If performance is in an intermediate range, further
evaluation and, ideally, training would be offered to assist in overcoming
performance deficiencies. The applicant should then have the opportunity to
demonstrate his/her on-the-road ability to compensate for the tested
deficiencies. The licensing authority may then grant an unrestricted license; a
license restricted to certain conditions, destinations, are as, or equipment; or
deny licensing. Performance in the lower range would suggest a combination of
abilities too limited for licensure, unless exceptional circumstances warrant
further consideration.
The license to drive a car on public roads is a privilege
rather than a right. It should not be extended indiscriminately. Nevertheless,
in a society where the personal vehicle is the primary, and often the only mode
of transportation, cessation of driving results in personal hardship (7), and
licensure should not be withheld without clear justification.
References
1. Ball K. et al., Age and Visual Search: Expanding the Useful
Visual field of View, J Opt Soc Am.A, 1988; 5:2210-19.
2. Ball K. et al., Visual Attention Problems as Predictors of
Vehicle Crashes in Older Drivers. Investigative Ophth & Visual Science,
1993; 43: 11, 3110-3123.
3. Duchek J. M., et al, Attention and Driving Performance in
Alzheimer's Disease. J. Gerontol, 1988; 53B:130-41.
4. Gronda S., Samson S., Withrow J., Getting in Gear, St.
Petersburg, FL: Area on Aging of Pasco-Pinellas, Inc., 2000.
5. Lyons J. Vision and Driving Report for the Motor Vehicle
Administration, State of Maryland, 1995.
6.. Marottoli R.A., Development of a Test Battery to Identify
Older Drivers at Risk for Self-Reported Adverse Driving Events, J Am Ger Soc,
1988; 46:562-68.
7. Marottoli R. A., Ostfeld A.M., Merritt S. S., Driving
Cessation and Changes in Mileage Driven Among Elderly Individuals. J. Geront,
1993; 48:S255-S260.
8. Owsley C. et al, Visual Processing Impairment and Risk of
Motor Vehicle Crash Among Older Adults, JAMA, 1998; 279:14, 1083-1088.
9. Charman, W. N., Vision and Driving - A Literature Review
and Commentary, Ophthalmic Physiol Opt, 1997; 17:371-391.
10. Owsley C., McGwin J. G., Vision Impairment and Driving
Survey of Ophthalmology, 1999; 43:6, 535-50.
11. Owsley C., Sloane M. E., Contrast Sensitivity and the
Perception of Real-World Targets, Br J Ophth, 1987; 71:791-796.
12. Owsley C. et al., Visual Risk Factors For Crash
Involvement In Older Drivers With Cataract, Archives of Ophthalmology in press,
2001.
13. Raleigh R., Development and Testing of a Model Driver
Licensing Program in Maryland, Gerontological Society of American, Symposium on
Driving Assessment; Washington, DC, 2000.
14.
Szlyk J. P., Fishman G. A., Severing K., Evaluation of
Driving Performance in Patients with Juvenile Macular Dystrophies, Arch Ophth,
1993; 111:207-12.
15. Vingrys A. J., Cole B. L., Are Color Vision Standards
Justified in the Transport Industry? Ophthalmic Physiol Opt, 1988; 8:257-74.
16. Johnson C.A., Keltner, J. L., Incidence Of Visual Field
Loss In 20,000 Eyes And Its Relationship To Driving Performance, Arch Ophth,
1983; 101 371-375.
Approved by: Board of Trustees, October 2001 | 
