Although there is little evidence to support an association between
vision and car accidents, a vision screening law in Florida that
targets drivers age 80 and older seems to have reduced the number of
adults in this age range who die from motor vehicle collisions. The
findings are published in the November issue of Archives of
Ophthalmology.
“Older drivers represent the fastest-growing segment of the driving
population,” write Gerald McGwin Jr., M.S., Ph.D. (University
of Alabama at Birmingham) and colleagues. “As this segment of the
population expands, so too have public safety concerns, given older
drivers’ increased rate of motor vehicle collision involvement per mile
driven. Research has suggested that this increase may be partly
attributed to medical, functional and cognitive impairments.”
Visual acuity has not been firmly linked to involvement in motor
vehicle collisions, but that did not stop the State of Florida from
implementing a law that required vision tests for drivers 80 years and
older before renewing licenses in 2004. This change in law combined
with data from the National Highway Traffic Safety Administration and
the U.S. Census Bureau on rates of motor vehicle collision deaths from
2001 to 2006 provided McGwin Jr. and colleagues the necessary tools for
a quasi-experimental analysis. The researchers also looked at death
rates from motor vehicle accidents in Alabama and Georgia, neighboring
states that had no change in license renewal policy.
Between 2001 and 2006, Florida saw an overall but non-significant
increase in its overall death rate from motor vehicle collisions.
However, drivers age 80 and older demonstrated a linear decrease in
this rate. Compared to the period before the law (from 2001 to
2003), the fatality rate in the period after the law (from
2004 to 2006) among all drivers increased from 14.61 per 100,000
persons
per year to 14.75 per 100,000 – a 6% increase. The rate specific to
older drivers decreased from 16.03 per 100,000 persons per year to
10.76 per 100,000 – a 17% decrease. In the comparison states, Alabama
and Georgia, there was no change in death rates among older drivers.
The authors try to explain the decrease in the decrease in death rates
among older Floridian drivers: “Perhaps the most apparent reason is
that the screening law removed visually impairment drivers from the
road…However, in reality, the situation is significantly more
complex.”
According to the authors, only 7% of drivers were unable to receive a
license renewal. This means that only a small percentage of drivers
were removed from the road because of failure to meet vision standards.
In addition, it is possible that many drivers who did not pass the
vision requirement sought vision care and were able to receive a
license after being treated. This could have improved overall vision
function of drivers. A third suggestion is that drivers with poor
vision selected themselves to be removed from the road because they
assumed that they would not receive a renewal.
“Ultimately, whether the vision screening law is responsible for the
observed reduction in fatality rates because of the identification of
visually impaired drivers or via another, yet related, mechanism may be
inconsequential from a public safety perspective,” conclude the
researchers. “However, the importance of driving to the
well-being of older adults suggests that isolating the true mechanism
responsible for the decline is in fact important.”
The Impact of a Vision Screening Law on Older Driver Fatality
Rates
Gerald McGwin Jr; Scott A. Sarrels; Russell Griffin; Cynthia Owsley;
Loring W. Rue III
Archives of Ophthalmology (2008).
126[11]: pp. 1544 – 1547.
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: Peter M Crosta