FOR RELEASE AT 4 P.M. ET, MONDAY, MARCH 22, 1999
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Vision Problems, Not Confusion, Cause Alzheimer's Patients to Become Lost
ST. PAUL, MN -- One of the most debilitating effects of Alzheimer's disease is a tendency to become lost in familiar surroundings. Medical researchers have commonly attributed this loss of orientation to mental confusion. However, a new study suggests that people with Alzheimer's become lost not because they are confused, but because their vision is impaired.
The condition, called "motion blindness," may be the result of isolated damage in one part of the brain, according to the study published in the March 23 issue of Neurology, the scientific journal of the American Academy of Neurology.
"This study gives us a whole new insight into what's going wrong with the brain in Alzheimer's, and also gives us a way to measure how debilitated an individual will be by the disease," said neurologist and study author Charles Duffy, MD, PhD, of the University of Rochester in New York.
Researchers studied the ability of six healthy young people, 12 healthy elderly people and 11 people with Alzheimer's disease to see and interpret visual patterns. In one test, participants viewed a panoramic computer display with radiating patterns of visual motion simulating what you see as you move through your surroundings. Participants were then asked whether it looked like they were moving to the left or the right. The Alzheimer's patients had more than twice as much difficulty interpreting the patterns than either the healthy young people or the healthy elderly.
The researchers also tested the participants' spatial navigation by walking them from the hospital lobby to the lab, telling them they would be asked questions about the route. The young people were able to answer correctly 88 percent of the time and the healthy elderly 73 percent of the time. But the Alzheimer's patients answered correctly only 32 percent of the time.
The researchers concluded that Alzheimer's greatly impairs the ability to see what they call the radial patterns of optic flow, or the spatial patterns of visual stimulation healthy people use to orient themselves.
This study counters the generally accepted impression that Alzheimer's is just a memory disorder, Duffy said. He said, "People with Alzheimer's get lost not because they don't remember where they've been, but because they can't see where they're going."
This visual disorientation is often one of first symptoms that shows up in Alzheimer's patients; therefore, it could be useful in early diagnosis of the disease. The tests could also be used to identify those at particular risk for getting lost, Duffy said, such as those who shouldn't be driving due to their visual disorientation.
The researchers have also begun studying the hypothesis that the visual impairment of Alzheimer's patients is so specific that patients may have retained other perceptual mechanisms or strategies for finding their way around, Duffy said. Identifying those might suggest ways to retrain Alzheimer's patients to use other clues to find their way, he said.
Improving care for patients with neurological disorders through education and research is the goal of the American Academy of Neurology, an association of more than 15,000 neurologists and neuroscience professionals.
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