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| Researchers hope that eye exams could one day help screen people in their 40s and 50s for the possibility of later developing Alzheimer's disease long before symptoms appear |
Advances in
eye exam technology could one day help doctors diagnose people with Alzheimer's
disease long before symptoms appear, researchers said Thursday.
Using
equipment similar to the kind already available at most eye doctors' offices,
researchers detected signs of Alzheimer's in a small sample of 30 people,
according to a study published in the Journal of the American Medical
Association (JAMA) Opthalmology.
Those
enrolled in the study -- all in their mid-70s with no outward symptoms of
Alzheimer's -- underwent PET scans or sampling of spinal fluid.
About half
came back with elevated levels of the Alzheimer's proteins amyloid or tau,
suggesting they would eventually develop dementia.
In this
group, researchers also found thinning in the retina, something that experts
had previously seen in autopsies of people who died from Alzheimer's disease.
"In
the patients with elevated levels of amyloid or tau, we detected significant
thinning in the center of the retina," said co-principal investigator
Rajendra Apte, professor of ophthalmology and visual sciences at Washington
University in St. Louis.
"All
of us have a small area devoid of blood vessels in the center of our retinas
that is responsible for our most precise vision. We found that this zone
lacking blood vessels was significantly enlarged in people with preclinical
Alzheimer's disease."
The study
did not, however, reveal if the participants with thinning retinas went on to
develop Alzheimer's or not.
For that
reason, Doug Brown, chief policy and research Officer, Alzheimer's Society,
called the area of research "fascinating" but sounded a note of
caution.
"Without
confirming that any of the people with preclinical Alzheimer's actually went on
to develop the disease, we would need to see this carried out on a much larger
group over a longer period of time to draw any firm conclusions," said
Brown, who was not involved in the study.
Sara
Imarisio, head of research at Alzheimer's Research UK, agreed.
"While
the eye tests used in this research are relatively quick, inexpensive and
non-invasive, as only 30 people took part in the study, we still need to see
more research before we can tell how useful this method could be for
highlighting early signs of Alzheimer's"
Dementia
on rise
Experts say
brain damage from Alzheimer's disease can begin up to two decades before signs
of memory loss appear.
Close to 50
million people are living with dementia around the globe, and the toll is
expected to mount in the coming decades as the population ages.
Alzheimer's
is the most common form of dementia, and there is no cure. But earlier
detection may make it possible for drug or lifestyle interventions that may
stave off the disease.
Currently,
doctors use PET scans and lumbar punctures to help diagnose Alzheimer's -- both
expensive and invasive techniques.
The type of
technology used in the JAMA study is called optical coherence tomography
angiography (OCT-A).
It is
commonly used to shine light into the eye so that a doctor can measure the
thickness of the retina and optic nerve.
Researchers
say the retina and central nervous system are interconnected, so changes in the
brain can be reflected in the cells of the retina.
"This
technique has great potential to become a screening tool that helps decide who
should undergo more expensive and invasive testing for Alzheimer's disease
prior to the appearance of clinical symptoms," said the study's first
author Bliss E. O'Bryhim, a resident physician in the Department of
Ophthalmology and Visual Sciences at Washington University.
The study
authors agree that more work is needed to confirm if the technique works in
larger populations, but are hopeful that it could one day help screen people in
their 40s and 50s.
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