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“Snapshots” of eyes could serve as early
warning of Diabetes
Newswise — A new vision screening device,
already shown to give an early warning of
eye disease, could give doctors and patients
a head start on treating diabetes and its
vision complications, a new study shows.
The instrument, invented by two scientists
at the University of Michigan Kellogg Eye
Center, captures images of the eye to detect
metabolic stress and tissue damage that
occur before the first symptoms of disease
are evident.
For people with diabetes — diagnosed or not
— the new device could offer potentially
significant advantages over blood glucose
testing, the “gold standard” for diabetes
detection.
The device takes a specialized photograph of
the eye and is non-invasive, taking about
five minutes to test both eyes.
In the July issue of Archives of
Ophthalmology, Victor M. Elner, M.D., Ph.D.,
and Howard R. Petty, Ph.D., report on the
potential of the new instrument to screen
for diabetes and determine its severity.
If further testing confirms the results to
date, the new instrument may be useful for
screening people who are at risk of diabetes
but haven’t been diagnosed.
“Our objective in performing this study was
to determine whether we could detect
abnormal metabolism in the retina of
patients who might otherwise remain
undiagnosed based on clinical examination
alone,” says Elner, professor, Department of
Ophthalmology and Visual Sciences at U-M
Medical School.
Metabolic stress, and therefore disease, can
be detected by measuring the intensity of
cellular fluorescence in retinal tissue.
In a previous study, Petty and Elner
reported that high levels of flavoprotein
autofluorescence (FA) act as a reliable
indicator of eye disease.
In their new study, Elner and Petty measured
the FA levels of 21 individuals who had
diabetes and compared the results to
age-matched healthy controls.
The Kellogg scientists found that FA
activity was significantly higher for those
with diabetes, regardless of severity,
compared to those who did not have the
disease.
The results were not affected by disease
severity or duration and were elevated for
diabetics in each age group: 30 to 39 years,
40 to 49 years, and 50 to 59 years.
Given the increasing prevalence of diabetes,
the FA device holds the potential to help
address a leading and growing public health
concern.
Some 24 million Americans have diabetes and
an additional 57 million individuals have
abnormal blood sugar levels that qualify as
pre-diabetes, according to the latest report
from the Centers for Disease Control and
Prevention.
In
addition, 4.1 million people over the age of
40 suffer from diabetic retinopathy, an
eye-related complication of diabetes that is
the leading cause of blindness among
working-age adults.
Twelve individuals in the study were known
to have diabetic retinopathy, a disease in
which blood vessels in the eye are damaged.
The individuals with diabetic retinopathy in
at least one eye had significantly greater
FA activity than people with diabetes who do
not have any visible eye disease.
“The abnormal readings indicated that it may
be possible to use this method to monitor
the severity of the disease,” says Elner.
Petty, a biophysicist and imaging expert,
explains that hyperglycemia — or high blood
sugar — is known to induce cell death in
diabetic tissue soon after the onset of
disease but before symptoms can be detected
clinically.
“Increased FA activity is the earliest
indicator that cell death has occurred and
tissue is beginning to break down,” says
Petty, professor of Ophthalmology and Visual
Sciences, and professor of Microbiology and
Immunology at the U-M Medical School.
“FA serves as a ‘spectral-biomarker’ for
metabolism gone awry, and we can use the
results to detect and monitor disease.”
Petty also observes that unlike glucose
monitoring, elevation of FA levels reflects
ongoing tissue damage.
That knowledge, he says, could motivate
patients to intensify their efforts to
manage the disease.
The Michigan researchers also note that
elevated FA does not always mean that an
individual has diabetes.
“Because of the prevalence of diabetes in
our population, individuals with abnormally
high FA would be prompted to undergo glucose
tolerance testing,” says Elner. “If the
findings were negative for diabetes, we
would look for other causes of ocular tissue
dysfunction.”
Both Elner and Petty agree that the device
has great potential as a tool for diabetes
screening and management. “So much damage
occurs before the disease can be detected by
a doctor,” says Elner.
“Early diagnosis will allow us to reduce
organ damage and prevent many complications
that accompany this disease.”
Elner and Petty have filed for patents and
have formed a company, OcuSciences, Inc., to
commercialize the metabolic imaging
instrument.
Reference: “Rapid, Non-invasive Detection of
Diabetes-induced Retinal Metabolic Stress,”
Archives of Ophthalmology, July 2008, Vol.
126, No. 7, pp. 934-938.
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