A new, noninvasive eye test could someday lead to the detection of Alzheimer's disease in its earliest stages. The test may allow patients to start treatment earlier, and it could also hasten the development of new Alzheimer's drugs.
Alzheimer's disease, the most common form of senile dementia, affects more than 18 million people worldwide. As life expectancy continues to increase, this number is expected to climb rapidly over the next few decades. The new eye test was developed after researchers at Brigham and Women's Hospital in Boston, Mass., discovered that the protein responsible for causing Alzheimer's disease is present not only in the human brain, but also in the lens of the eye.
While the exact cause of Alzheimer's is unknown, most experts attribute it to the development of plaques or tangles in the brain. These structures, which interrupt the flow of messages between brain cells, are created by the accumulation of protein fragments called beta amyloid. According to Lee Goldstein at the Center for Ophthalmic Research at Brigham Women's Hospital, "We've known for years that beta amyloid causes the formation of plaques in the brain, but we've only recently discovered that it also creates a very unusual cataract on the edge of the eye's lens."
Goldstein made the surprising discovery after he found cataracts in both eyes of a laboratory mouse with the animal equivalent of Alzheimer's disease. Dissection of the cataracts revealed that they contained beta amyloid protein. The cataract associated with Alzheime's disease, called a supranuclear cataract, is different from common, agerelated cataracts of the eye. Age-related cataracts develop in a separate location on the lens and do not contain beta amyloid protein. "This isn't your run-of-the-mill, garden-variety cataract," Goldstein pointed out. "It doesn't cause problems with your vision, and it cannot be detected during a routine eye examination." The new test employs a technique known as quasielastic light scattering, which uses low-power infrared laser light to detect beta amyloid protein particles in the lens of the eye. The test is quick, painless and with the proper equipment, easily performed by medical professionals. Goldstein, who has had the test performed on his eyes on several occasions, said, "It's safe, and it's not the least bit uncomfortable. As you focus your eyes on a visual target, you experience a vague sensation of a red pulsation that lasts for less than a second." Currently, the test is considered to be an investigational technique and is not yet approved for widespread use. If the results of ongoing clinical trials are favorable, it's likely that the eye test will be available at ophthalmologists' offices around the country in the very near future.
Goldstein, an assistant professor of psychiatry at Harvard Medical School, said that the ability to detect beta amyloid protein in the lens of the eye represents a tremendous step forward in the search for a cure for Alzheimer's."The good news is that we understand a great deal about this disease, and there are hundreds of treatments in various stages of research and development," he said. "The real obstacle is not the lack of potential therapies for the disease; it is the lack of good diagnostic tests to tell us which patients can benefit from these therapies."In order to be successful, treatment for Alzheimer's must be started early, before brain cells are irreversibly damaged. "By the time the first symptoms appear, the disease is already in an advanced state," Goldstein said. "At that point, it's been going on for years, or even decades."While beta amyloid plaques in the brain are difficult to visualize, even with modern brain scanners, beta amyloid cataracts in the eyes' lenses are relatively easy to detect. In addition, the beta amyloid buildup in the lens may occur long before the protein begins to form plaques in the brain."The lens of the eye is more metabolically sluggish than the brain," Goldstein explained. "It's not as effective at ridding itself of the beta amyloid protein." Goldstein has little doubt that current research will lead to a cure for Alzheimer's disease. "This is not some distant fantasy," he said. "This is something that's going to happen in the very near future."In the meantime, he stressed that one of the best ways to protect yourself from Alzheimer's disease is to keep your body healthy and your brain actively engaged. "Work crossword puzzles or explore the Internet," he said. "It's important to keep learning new and different things to challenge your mind."Rallie McAllister is a family physician in Kingsport, Tenn.Source: Buffalo News. Powered by Yellowbrix.
Source: Health & Wellness
