Scanning the eyes with lasers could help detect signs of Alzheimer's disease even before symptoms of the neurological illness appear in the brain.
These laser tests could improve patients' chances of starting Alzheimer's treatments early, before the onset of irreparable damage to the brain.
"We need to catch the disease before symptoms emerge to give us the greatest chance to alter its course and ultimately cure it," researcher Lee Goldstein, an interdisciplinary neuroscientist at Harvard Medical School, told LiveScience.
In 2003, Goldstein and his colleagues discovered that the same malformed amyloid beta proteins that are hallmarks of Alzheimer's disease can also be found in the eye's lens and its surrounding fluid.
Last year, they revealed a pair of non-invasive tests that scan the eye for these tell-tale molecules to potentially detect the disease in its earliest stages.
Both tests very briefly shine a low-power near-infrared laser into the eye. The light is safe, not visible to the patient, and does not cause any discomfort.
One test scans for clumps of the aberrant protein in part of the lens where it collects to form cataracts.
The other test is used in conjunction with special eye drops that bind only to the protein molecules and fluoresce in response to the laser.
While the eye-drop test provides more detailed molecular information about the proteins, the first test yields more biophysical data, such as the number and size of the particles.
In his latest experiments, Goldstein and his colleagues found that they could pick up signs of the malformed proteins in the eyes of mice even before they began accumulating in the mice's brains.
The researchers have also recently completed initial human clinical trials of their tests.
The tests are slated to enter phase III multicenter human clinical trials over the next year.
In the end, the tests might cost less than $300 per patient.
Goldstein hopes they can become a routine part of annual physical exams, starting in patients' middle age.
He is co-founder of Neuroptix, a company that is developing these tests for clinical use, although Goldstein is not receiving any sponsorship from the company.
Goldstein noted the tests could also potentially speed up the development of new Alzheimer's drugs by giving investigators rapid feedback on whether medicine being tested is doing its job of removing the harmful proteins from the body.
"We're having great difficulty testing the many drugs against Alzheimer's we have in the pipeline right now," he said. "Testing is the real bottleneck when it comes to developing these drugs."
Goldstein will present his team's latest findings on Oct. 9 at the annual meeting of the Optical Society of America in Rochester, N.Y.
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