Study Finds Many People With Hemianopia Have Difficulty Detecting Pedestrians While Driving, Advocates for Individual Testing

Study Finds Many People With Hemianopia Have Difficulty Detecting Pedestrians
While Driving, Advocates for Individual Testing

BOSTON, Nov. 12 /PRNewswire-USNewswire/ -- Scientists at Schepens Eye Research
Institute have found that -- when tested in a driving simulator -- patients
with hemianopia (blindness in one half of the visual field in both eyes) have
significantly more difficulty detecting pedestrians (on their blind side) than
normally sighted people. These results, published in the November 2009 issue
of Investigative Ophthalmology and Visual Science, fly in the face of some
recent on-road studies that have found most people with hemianopia safe to
drive.

"The results are important because they mean we need to continue to look
carefully at people with this condition and evaluate them individually to
determine their fitness to drive," says Dr. Eli Peli, principal investigator
of the study and senior scientist at Schepens Eye Research Institute.

In at least 22 states and many other countries, people with hemianopia are
prohibited from driving because they do not meet the visual field requirements
for licensure.

"Our study urges caution in opening the door for people with hemianopia to
start or continue driving again," says first author, Dr. Alex Bowers, who is
an Assistant Scientist at Schepens. She and Peli believe the Schepens study,
because it was conducted in the safety of a driving simulator over a longer
period of time and "miles" than a typical "on-road" study, provides new
insights into detection failures of drivers with hemianopia. These detection
failures might not be revealed in a short on-road test in which there is
little control over the appearance of potential "blind-side" hazards.

More than a million people suffer from hemianopia, a condition in which one
half of the visual field in both eyes is blinded, usually the result of a
stroke or head injury. People with hemianopia often do not know what they
can't see and frequently bump into and trip over objects while walking.
Driving is a whole other challenge.

Peli and his research team compared 12 subjects with hemianopia to 12 visually
normal people, matched by age, sex, and years of driving experience. All
subjects drove for about 120 minutes along city roads and rural highways.
During the journey pedestrians appeared at random intervals along the roadway
and at intersections.

Subjects pressed the horn button every time they saw a pedestrian. The team
then measured detection rates and response times based on these horn-press
responses.

The scientists found that drivers with hemianopia had much lower detection
rates on their blind side than normally sighted subjects (or their own seeing
side), detecting on average only about 45% of pedestrian figures. When
pedestrians were seen on the blind side, response times were about twice as
long as those of the normally sighted drivers. They also found a large
variability in blind-side detection rates among the individuals with
hemianopia (from 6% to 100%) with the lower rates found among the older
subjects.

Although overall most subjects with hemianopia had detection rates that seem
incompatible with safe driving, Bowers cautions that "the relationship of our
simulator detection performance measures to on-road performance has yet to be
established, another reason to treat each person with hemianopia individually
as they seek approval to get back on the road."

The next step for the team is to determine whether an optical aid that
expands the visual field - peripheral prism (expansion prism EP) glasses -
might be a useful device for drivers with hemianopia. Specifically, they plan
to conduct another driving simulator study to investigate whether drivers with
hemianopia have better detection rates for pedestrians on the blind side when
using the glasses than when driving without them.

The study's authors are-- Alex Bowers, Aaron Mandel, Robert Goldstein and Eli
Peli.

Schepens Eye Research Institute is an affiliate of Harvard Medical School and
the largest independent eye research institute in the nation.

SOURCE Schepens Eye Research Institute

Patti Jacobs, +1-617-864-2712, pjacobs12@comcast.net, for Schepens Eye
Research Institute