Maybe you’ve noticed that street signs look blurry at night when you’re driving. Or maybe tiny dark spots have appeared in your vision. These are among the signs of retinopathy, a common eye complication of diabetes. Often there are no symptoms.
You might even have 20/20 vision and have advanced retinopathy, says Emily Chew, MD, deputy clinical director at the National Eye Institute, part of the National Institutes of Health. Left untreated, retinopathy can lead to vision loss and blindness. That’s why it’s important for people with diabetes to have a yearly dilated eye exam, in which an eye doctor looks for damage. And with advances in diabetes management, eye screenings, and treatment, many people with diabetes may be able to avoid diabetic retinopathy altogether or to slow or stop its progression.
Into the Eye
Diabetic retinopathy is brought on by chronically elevated blood glucose levels that, over time, damage blood vessels in the retina at the back of the eye and cause blurred or cloudy vision or, eventually, complete loss of vision, says Richard Rosen, MD, director of retina services at the New York Eye and Ear Infirmary of Mount Sinai.
n the first stage of the disease, small areas of swelling occur in the retina’s tiny blood vessels. As a response to the damage, the immune system sends red and white blood cells into the small capillaries responsible for nourishing the eye tissue and clogs them. “This starts to shut down the capillaries, and then you get areas that don’t have adequate circulation, oxygen, and other nutrients,” Rosen says.
The lack of circulation causes weakened blood vessels in the eye to leak. As the disease progresses, fragile, rapidly growing blood vessels form on the retina, bleeding and leaking fluid into the eye. Fluid leakage from retinal blood vessels can result in swelling in the part of the eye responsible for central vision, called macular edema, says Chew.
People with diabetes hold the greatest power in keeping their eyes healthy. “If you can stay in good blood glucose control, it’s better than any drugs we can give,” Chew says. In recent years, clinical trials have shed light on how to prevent diabetic retinopathy and its progression.
The Action to Control Cardiovascular Risk in Diabetes (ACCORD) Eye Study found that tight glucose control in adults with type 2—an average A1C of 6.4 percent—reduced the risk of diabetic retinopathy progression by up to 70 percent, compared with those whose average A1C was 7.7 percent.
Interestingly, even though the average A1C (a measure of blood glucose over time) of the tight-control group rose to around 7.8 percent four years after the trial, the group continued to have a 50 percent lower risk of diabetic retinopathy progression. “It’s what we call a metabolic memory, or legacy effect, that continues,” says Chew, the study’s lead author. “It’s really worth it to put that money in the bank [and get your glucose under control] when first diagnosed with diabetes.” Other studies have shown tight control reduces the risk of retinopathy in people with type 1 diabetes as well.
According to a 2017 American Diabetes Association position statement on diabetic retinopathy, published in the March issue of Diabetes Care, maintaining blood pressure of 140 mmHg or lower has been shown to decrease retinopathy progression in people with type 2.
Most ophthalmologists screen for retinopathy by taking a picture of the retina to see if any blood spots are visible. In the last two years, a new form of imaging, called optical coherence tomography angiography, or OCTA, has emerged. It’s not yet widely available but can detect diabetic retinopathy long before vessels start leaking blood and fluid.
This new technology allows your doctor to see into the retina to examine blood flow, swelling, and whether your eye is losing blood vessels, Rosen says. Your ophthalmologist can also measure how the disease has progressed at each visit. “We can tell if [the person] is losing capillaries—and how fast,” says Rosen.
You’ll receive laser treatment when abnormal blood vessels start to grow on the retina. The laser burns 1,000 to 2,000 tiny spots on the outer areas of the retina in order to shrink the fragile, bleeding blood vessels. This saves central vision but sacrifices peripheral, or side, vision.
An experimental treatment may provide an alternative. Instead of burning areas of the retina to get rid of leaky blood vessels, researchers use low-intensity micro-pulses to treat the growth of blood vessels and the swelling in the retina. The idea is that low-level laser energy in the eye could slow the growth of fragile blood vessels and reduce swelling without damaging the tissue responsible for peripheral sight, says Rosen.
A treatment for retinal swelling (macular edema) may hold promise for abnormal blood vessel growth. The FDA recently approved for retinopathy treatment Lucentis, an anti-vascular endothelial growth factor (anti-VEGF) drug that is injected directly into the eye and works to stop damaged blood vessels from leaking (the drug was already approved to treat macular edema). It may reduce the growth of blood vessels and, in some cases, improve vision more than the traditional laser treatment, says Chew. Now, pharmaceutical companies are investigating how to extend the length of time these drugs work in the body to limit office visits. Rather than monthly injections, the aim is to go six months or longer between treatments, says Rosen.
Drug trials are also underway to treat early stages of the disease, most likely with oral medication, which is more appealing than anti-VEGF injections. Researchers have identified molecules that can affect how the capillaries become clogged with red and white blood cells. The goal is to prevent capillaries from closing or to reopen them. “If we can address the disease right at the beginning, then we can change the whole course of it,” says Rosen.
Don’t wait until you notice vision loss, dark spots, or other abnormalities to see an ophthalmologist. With regular screenings, your doctor can detect eye disease early and help to preserve your vision. The American Diabetes Association’s 2017 Standards of Medical Care recommends:
- Adults with type 1 have a dilated eye exam within five years of their diabetes diagnosis.
- Kids who’ve had type 1 diabetes for three to five years should get a comprehensive eye exam at age 10 or after puberty has begun, whichever is earlier.
- People with type 2 have a dilated eye exam at the time of their diabetes diagnosis.
- People with type 1 and 2 have annual dilated eye exams. If there is no evidence of retinopathy for one or more annual exams and blood glucose is well managed, doctors may recommend eye exams every two years.
- Women with diabetes receive an eye exam before becoming pregnant or in the first trimester. Pregnancy can hasten the start or progression of diabetic retinopathy.