Victims of hemianopia may not to be able to detect pedestrians easily while driving.
Hemianopia is a condition in which one half of the visual field in both eyes is blinded, usually the result of a stroke or head injury.
Scientists from Schepens Eye Research Institute have found patients with hemianopia have significantly more difficulty detecting pedestrians (on their blind side) than normally sighted people.
"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," said 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," said first author, Dr. Alex Bowers, who is an Assistant Scientist at Schepens.
During the study, research team compared 12 subjects with hemianopia to 12 visually normal people.
All the participants 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.
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 45pct 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 6pct to 100pct) with the lower rates found among the older subjects.
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.
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 results are published in the Investigative Ophthalmology and Visual Science.