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Almost 8% of individuals with pre-diabetes have detectable early diabetic retinopathy, according to research presented June 12 at the 65th Scientific Sessions of the American Diabetes Association (ADA) in San Diego.
Among those with very early diabetes (diagnosis within 6 to 12 months of the onset of diabetes), almost 13% have diabetic retinopathy, investigators found.
"A good retinal exam for patients as they transition from pre-diabetes to very early diabetes is important because it's clear that retinopathy is happening there, and that was very underappreciated prior to these results," reports Richard Hamman, MD, DrPH, of the University of Colorado School of Medicine.
ADA's chief scientific and medical officer, Richard Kahn, PhD, says the big news is finding that the complications of diabetes begin years before a typical diagnosis. "We have not known when the changes start to occur," he says.
Previous research shows as many as one-third of patients diagnosed with diabetes have some degree of eye disease, and almost 5% at presentation have more advanced eye disease, says Emily Chew, MD, of the National Eye Institute, which funded the study.
It can be hard for primary care clinicians to see the early signs of retinopathy, Chew says. "Because we don't know how long most patients have had diabetes, as soon as they are diagnosed they should always be evaluated" for eye disease, she says. Then the message that patients need to be in good control of their blood glucose, blood pressure, and lipids can come from both their regular physician and their eye doctor.
THE EVIDENCE
The retinopathy study is a follow-up of the Diabetes Prevention Program (DPP) trial of 3,234 people with impaired glucose tolerance and elevated fasting glucose, now called pre-diabetes.1
The DPP Outcomes Study has followed almost 90% of those patients since the original DPP ended in 2001. It tests participants every 6 months for fasting blood glucose and every year with an oral glucose tolerance test, which helps accurately date the onset of diabetes.
In a random sample of DPP participants, fundus photographs from 302 subjects with pre-diabetes (blood glucose 100–125 mg/dl) showed 7.6% had lesions that indicated early diabetic retinopathy, the leading cause of blindness in adults. Photos from 588 people who developed diabetes (blood glucose >126 mg/dl) showed 13% had retinopathy. The mean age of the subjects was about 54 years.
Researchers also observed a relationship between the presence of retinopathy and higher blood pressure and higher glycated hemoglobin (A1C) among those with early diabetes, notes DPP vice chair Hamman. "This suggests to us that some of the same risk factors are operating very early in the course of diabetes and emphasizes how important good blood pressure and good blood [glucose] control are very, very early."
Finally, the appearance of retinopathy in patients with pre-diabetes, and the suggestion that lesions are present at glucose levels below the current diagnostic thresholds for diabetes, could lead experts to reconsider those limits, Hamman says.
But because the study looked at a relatively small sample of people with
pre-diabetes, and because "we're not completely sure of the natural
history of these early lesions," Hamman says it may be too early to
reset the diabetes cut-points. 
Footnotes
ADA retinopathy recommendations:
Source: American Diabetes Association: Standards of medical care in diabetes (Position Statement). Diabetes Care 28 (Suppl. 1):S4–S36, 2005.
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