The eyes, long described as the windows to the soul, appear to be windows to the brain, as well: Scientists have developed an eye-scan technique that may detect Alzheimer's disease at its earliest stage, before major symptoms appear.
With early detection, a person could seek treatment for Alzheimer's at a time when therapies would be most effective at slowing the progression of the memory-robbing disease, the researchers said.
The research was presented today (May 5) at the annual meeting of the Association for Research in Vision and Ophthalmology (ARVO) in Seattle.
Alzheimer's disease, the most common form of dementia, is an epidemic that shows no signs of abating, according to the Centers for Disease Control and Prevention. Death rates for Alzheimer's disease are increasing: More than 5 million Americans live with the disease, and by 2050, this number is projected to rise to 14 million, according to CDC statistics.
There is no cure for Alzheimer's, but medicines can slow the development of many of the classic symptoms, such as loss of memory and communication skills, mood swings and depression. [7 Ways the Mind and Body Change With Age]
The cause of Alzheimer's is unknown. The disease appears to be associated with the accumulation of misfolded proteins in the brain called beta-amyloid and tau. The misfolded proteins can form tangles in the neural network of the brain, disrupting normal communication between neurons.
Doctors can only be sure that a patient had Alzheimer's after he or she dies, because an autopsy is needed to provide definitive proof of the presence of these microscopic brain tangles. PET scans of the brains of living people can provide doctors with evidence that amyloid and tau are accumulating, but these scans are expensive and invasive, requiring the patient to be injected with radioactive tracers that bind with these proteins and glow during the scan.
In the new report, researchers in New England devised a different, noninvasive approach to finding Alzheimer's early, using optical coherence tomography (OCT), an established medical imaging technique used to observe microscopic details. The OCT machine can be configured to painlessly scan a patient's retina, the tissue in the back of the eye, to look for abnormalities.
The researchers recruited 63 study participants who were at high risk for Alzheimer's disease, based on emerging symptoms and family history. The researchers first conducted PET scans to establish the extent of the participants' beta-amyloid accumulation. Then, they performed OCT scans and compared the results. [6 Foods That Are Good For Your Brain]
The researchers used a technique called blue laser autofluorescence in conjunction with the OCT, which causes certain cellular components to glow without requiring the injection of any dye or chemical tracer.
The OCT scan could not directly detect beta-amyloid proteins, but it did reveal shadow-like inclusion bodies — aggregates of cellular material, likely proteins — that correlated well with the level of beta-amyloid close to the retina revealed by the PET scan, according to Cláudia Santos, a graduate student at the University of Rhode Island who led the study.
"There is no treatment for Alzheimer's, [but] it may be because we are trying to intervene too late in the disease [process] and can't reverse the dementia," Santos told Live Science. This OCT technique "might be a good screening tool for preclinical Alzheimer's, since the OCT can be performed at any ophthalmologist clinic."
Santos said the OCT technique, once perfected, could be a first step in assessing the development of Alzheimer's disease. Should the OCT scan reveal evidence of beta-amyloid, doctors could then perform PET scans for a more thorough diagnosis and then prescribe medicines.
"Our study is longitudinal [conducted over time], so we will perform the OCT and PET scan again in about 20 months after these baseline results … to see [if] the level of amyloid-beta is increasing," Santos said. "We hope this study can be replicated with different subjects."
The research was conducted at Lifespan-Rhode Island Hospital in Providence and was co-led by Peter Snyder, a professor of neurology at Brown University, also in Providence.
Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.