An Eye on Alzheimer's

By Christine Gorman

When Ronald Reagan's physicians first suspected that the former President's memory lapses were caused by Alzheimer's disease, they had no easy way to confirm the diagnosis. To determine whether Reagan, now 83, had the degenerative brain disease that affects perhaps 4 million Americans, the doctors gave him a complex series of physical and psychological exams -- mainly to rule out other possible causes of his symptoms. A year passed before he was told that he was indeed in the early stages of Alzheimer's.

Now a group of researchers claim to have found a much easier method of detecting the disease. In a study published in last week's issue of Science, they report that Alzheimer's patients are unusually sensitive to a drug used by ophthalmologists to enlarge the pupils during eye exams. By measuring a person's response to the drug when it is dropped into the eye, physicians may be able to diagnose the dread disorder.

The idea for the eye test came from Huntington Potter, a neuroscientist at Harvard Medical School, who ingeniously followed up on an observation about people with Down syndrome, a genetic disorder that causes mental retardation. Potter knew that almost all Down patients who live long enough eventually develop brain lesions identical to those detected in autopsies of Alzheimer's sufferers. By scouring the scientific literature, he learned that people with Down syndrome are very sensitive to tropicamide, the drug used to dilate the pupil of the eye. Potter then approached Leonard Scinto, a neuroscientist now at Brigham and Women's Hospital in Boston, about the possibility of using the drug to spot Alzheimer's.

Together they studied 58 people whose ages averaged 72 and some of whom had already been given a diagnosis of Alzheimer's. After dropping a weak solution of tropicamide into their subjects' eyes, the researchers found the pupils in the healthy patients dilated only 4%, while the pupils of those with the disease opened at least 13%. Particularly telling was the case of a man whose eye-test results suggested that he had Alzheimer's but who had exhibited none of the symptoms -- until nine months later when his memory deteriorated dramatically.

It might seem futile to try to detect a problem for which there is neither a treatment nor a cure. However, neurologists estimate that at least 25% of all people who are told they have Alzheimer's actually suffer from some problem that can be treated, such as depression. A definitive test for Alzheimer's would advise doctors whether or not to keep looking for the source of patients' memory lapses.

Just as important, researchers are testing drugs that may slow mental deterioration in Alzheimer's patients. For those medications to work, however, physicians must administer them before there is any memory loss. "Otherwise, there isn't enough brain left for the drugs to work," Scinto notes. He and Potter plan to study 400 patients over the next year. If the eye test lives up to expectations, it could be on the market within the next two years.

With reporting by Andrea Dorfman/New York