Dear Doctor: I've heard that there's finally a test for Alzheimer's disease, and that it has to do with your eyes. What is it, and how does it work?
Dear Reader: Although researchers continue their search for a single and definitive diagnostic test for Alzheimer's disease, they haven't reached that goal at this time. However, they continue to make advances in the field, including recent studies that suggest impaired eye movement may be a predictive symptom in some cases. We don't yet have a cure for Alzheimer's disease, but early intervention has been linked to better outcomes for patients, including an improved quality of life. That makes any developments that aid in diagnosis important.
As most of you probably know, Alzheimer's is a progressive disease. Physical changes that occur within the brain gradually result in cognitive impairment and dementia. Although Alzheimer's disease is most often seen in older adults, it is not considered a normal part of aging. Symptoms include a decline in memory, thinking, speech, judgment, concentration and the ability to carry out tasks. The disease also results in changes to mood and personality. Other types of dementia and cognitive impairment share many of the same symptoms, which makes early diagnosis more challenging. A diagnosis of Alzheimer's involves a range of screening processes, including a neurological exam, tests to assess cognition and mental status, genetic testing and brain imaging scans. For some patients in the early stages of the disease, watchful waiting is a necessary -- and sometimes frustrating -- part of the process.
The study you're asking about looks into impaired eye movement as a diagnostic tool in at-risk patients. Participants with two different types of cognitive impairment were assigned visual tasks on a computer screen. For example, they were asked to look at the left side of the screen whenever a flashing icon appears on the right side. A device that can measure 500 eye movements per second then analyzed how well each person completed the task. The researchers found that the visual behavior of each group was unique enough that they could differentiate between the two types of dementia just by the results of the tests. Even more promising was the fact that the eye movement pattern in one type of dementia, where people struggled to look at the correct side of the screen, was similar to those with an Alzheimer's diagnosis.
The takeaway here is that eye tracking shows potential for predicting whether someone with mild cognitive impairment is likely to progress to Alzheimer's disease. That means instead of waiting for advancing symptoms, more patients could begin treatment earlier than is now possible.
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