Estudiante

Sensory Impairment and Driving:
The Blue Mountains Eye Study
Rebecca Q. Ivers, MPH, BOptom, Paul Mitchell, MD, and
Robert G. Cumming, PhD, MPH, MB
Drivers older than 79 years have a
higher accident rate when the rate is measured as a function of exposure, have accidents with more severe and more often fatal
consequences, and are more often judged as
legally responsible for causing anaccident
than are younger drivers.' In recognition of
the role that vision plays in driving, most
countries include a test of visual acuity in the
licensing procedure for car drivers. However, hearing impairment is not seen as a barrier to safe driving: in Australia, totally deaf
individuals may hold a driver's license.2
We aimed to describe the driving habits
of a defined older populationliving in the
Blue Mountains, west of Sydney, Australia,
and to examine the association between different types of visual impairment, selfreported problems with hearing, and selfreported car accidents.

Methods
The Blue Mountains Eye Study is a
population-based survey of eye disease in 2
postcode areas in the Blue Mountains, west
of Sydney, Australia. Details of the survey
methods andprocedures have been described
elsewhere.?5 Briefly, all noninstitutionalized
residents aged 49 years or older were identified by a private census. Of 4433 eligible
residents, 3654 (82.4%) attended the eye
examination.
Subjects completed an intervieweradministered questionnaire. They were asked
about their driving habits, accidents in the
last year, and hearing. A detailed eye examination wasconducted, including subjective
refraction,4 the Humphrey 76-point suprathreshold screening visual field test
(Humphrey Instruments, Inc, San Leandro,
Calif),5 and lens photography.6'7 The contrast
sensitivity of all subjects from the first postcode area (n = 2381) was measured with the
Vectorvision CSV-1000 chart (Vectorvision,
Inc, Dayton, Ohio).
Prevalence ratios8-10 adjusted for age
and sexwere calculated; 95% confidence
intervals are presented in this report. Appropriate clinical cutpoints were used to categorize all variables except for contrast sensitivity, which was dichotomized at the third
quartile.

Results
There were 3654 participants in the
Blue Mountains Eye Study; of these, 2379
(65.1%) reported that they were current drivers. People of both sexes tended to giveup
driving as they got older (31.6% of men and
29.8% of women aged 80 and over reported
having given up driving, compared with
4.5% of men and 8.7% of women aged 49 to
59 years). There were few people driving
with poor visual acuity and even fewer after
refraction (Table 1).
Of people who had stopped driving, 51
(11.5%) reported that they had stopped
because of problems with their vision.Their
vision was worse than that of people who
gave up driving for other reasons: best-eye
visual acuity was 33.1 letters and 45.9 letters, respectively (P = .0001).
Of 2326 current drivers who answered
questions about motor vehicle accidents, 134
(5.8%) reported an accident in the past 12
months. The percentage of people having car
accidents was 5.8% for people aged 49 to 59
years, 5.5%for those aged 60 to 69 years,
5.4% for those aged 70 to 79 years, and
9.1% for those aged 80 years and over.
Table 2 shows associations between
visual acuity, contrast sensitivity, hearing loss,
and self-reported car accidents; some of these
associations were statistically significant.
Visual field was not associated with increased
risk of accidents, nor was the presence of
cataract(data not shown). Of study participants, 37.7% reported having hearing loss.

Discussion
Findings from past studies of vision and
car accidents have been conflicting. Some
studies have found that impaired visual acuity
is predicfive of road accidents," while others
have found only weak associations. '2"3 Some
Rebecca Q. Ivers and Robert G. Cumming are with
the Department of Public Health...