Scientists don't know what causes Alzheimer's nor do they know how to cure it. Thus, their best defense against the degenerative disease is early detection and treatment. That was the focus for researchers presenting at the US Society for Neuroscience conference. With mice as their test subjects, they discovered that reduced retinal thickness was an early indicator of Alzheimer's, the BBC reported.
Responsive to light, the retina is located at the back of the eye (see picture) and contains cells, arranged in several layers, that transmit impulses to the optic nerve and onto the brain, where an image is formed.
"The retina is an extension of the brain so it makes sense to see if the same pathological processes found in an Alzheimer's brain are also found in the eye," said Dr. Scott Turner, whose team of researchers studied an area not previously associated with the neurological disease.
Using two groups of mice - one given Alzheimer's by genetic means, the other neurologically healthy - Turner and colleagues found a thinner retina in the diseased mice only. The retinal ganglion cell layer of the genetically engineered mice was nearly half its original size and the inner nuclear layer was reduced by more than a third.
Using the retina as a means of diagnosis is important because of its accessibility. Given the right tools, the researchers believe doctors could check for or diagnose Alzheimer's during a regular eye exam. Current tests are much more invasive, according to the BBC. Equally as important, reduction of the retinal cell layers occurred in the mice before the disorder advanced too far and dementia took over -- meaning alterations of the retina are an early indicator and gives those diagnosed more time to condition their brains to stave off the disease.
"This suggests a new path forward in understanding the disease process in humans and could lead to new ways to diagnose or predict Alzheimer's that could be as simple as looking into the eyes," said Dr. Turner.
Studying changes in retinal cells is also a means to predict glaucoma, a neurodegenerative disorder that causes blindness, the BBC reported.
The results of their research must still convert to human experiments before doctors can begin screening for eyesight, glaucoma, and Alzheimer's all during the same basic exam. If translatable, victims of neurlogical diseases and the dementia that follows will be given more time to retain their mental faculties as early detection has been shown to reduce later memory loss.
"We're hoping that this translates to human patients and we suspect that retinal thinning, just like cortical thinning, happens long before anyone gets dementia," Dr. Turner told BBC News.
Early this year, a graduate student from the University of Florida devised an even more basic test for Alzheimer's when she discovered that those with the disease couldn't smell peanut butter in one nostril. That test, however, is at the moment only a confirmation of an Alzheimer's diagnosis and not yet an instrument for early detection.
