8 Risk Factors for Diabetic Macular Edema
If you’ve been diagnosed with diabetes, losing your eyesight might not be the first thing you’re worried about. But it’s more common than you think: Two in five diabetics have diabetic retinopathy, a condition that damages the minuscule blood vessels at the back of the eye. Of those, 50% develop diabetic macular edema (DME)—it’s the most common cause of vision loss for diabetics. “DME affects people’s central vision—the ability to read, for example, and drive,” says Thomas Gardner, M.D., professor of ophthalmology and visual sciences at the University of Michigan.
Here’s what happens: In people with DME, “the retinal blood vessels stretch and form little pouches, called microaneurysms, which can leak blood into the retina itself,” says Ian Han, M.D., assistant professor of ophthalmology and visual sciences at the University of Iowa. He likens the process to “muddy water flowing through pipes”; the pipes can corrode and leak fluid, which in turn causes the retina to swell. The good news: “DME is highly treatable, and the prognosis is far better today than 10 years ago,” says Dr. Gardner. Get a head start on the disease by knowing these risk factors.
Risk: High Blood Sugar
Because DME is expressly a form of diabetic retinopathy, it means that high blood glucose levels—the root of diabetes—is a key risk factor. Ultimately, high blood glucose levels will affect your entire body, but it begins with those areas most vulnerable to changes in blood flow. “Every single organ in the body requires blood flow,” says Dr. Han. “But damage from rising blood sugar levels tends to occur to the smallest blood vessels first, like those in your eyes.”
Just as diabetes is a risk factor for hypertension (high blood pressure), hypertension can lead to diabetic macular edema by causing blockage in small veins leading to your retina. Over time, blocked and damaged blood vessels can leak fluid into the retina, compromising its ability to process light. “I tell patients that a normal retina is like a dry sponge—it’s thin and light,” says Dr. Gardner. “But with DME, it becomes like a soggy sponge—it swells,” resulting in distorted vision, blurriness, and other symptoms.
Risk: Low Blood Protein Levels
Hypoalbuminemia, or low levels of the blood protein albumin, can lead to a buildup of fluid in your retinal tissues, according to researchers at the Beetham Eye Institute at Harvard Medical Center. Made in your liver, albumin plays an essential role in preventing fluid from leaking out of your blood vessels. Hypoalbuminemia can be caused by inflammation in your body, or too little protein or calories in your diet, and is treated with medication as well as dietary and lifestyle changes.
While there is limited direct evidence that smoking cigarettes causes DME, experts believe there may be an indirect connection. “There isn’t too much evidence that smoking is a direct risk factor for DME,” says Dr. Gardner. “But generally speaking, people who smoke or drink heavily are often not taking care of themselves in other ways. So smoking might need to be addressed as a factor in other fundamental aspects of a patient’s diabetes.” Translation: Smoking is terrible for your health. Just don’t.
During pregnancy, blood pressure can rapidly swing from normal to high, placing stress on blood vessels throughout the body, including your eyes. And although gestational diabetes, which effects up to 10% of pregnancies in the U.S. annually, does not cause retinopathy, “we sometimes see an acceleration of existing retinopathy in young women who have been diabetic for a while and get pregnant,” says Dr. Gardner. One reason: Pregnancy may disrupt diabetes treatment, leading to hypertension.
Certain racial and ethnic groups, including African Americans, Hispanics, Native Americans, and Pacific Islanders, have a higher prevalence of diabetes than Caucasians, and African Americans are 50% more likely to develop diabetic retinopathy than non-Hispanic whites. Possible reasons include dietary choices, economic differences, and lack of access to preventive care. “Patients who don’t have access to preventive care might not be able to get something like an insulin pump,” says Dr. Han. Without the tools to control their diabetes, the risk of DME rises.
Risk: Fluid Retention
You know that edema, or swelling, in DME is brought about when blood from damaged vessels leaks into the retina. But those blood vessels don’t spontaneously begin oozing on their own. Instead, it’s the result of a pooling of fluid that increases pressure in your body’s tissues, causing them to swell. “Fluid retention from any cause increases capillary hydrostatic pressure, which in turn drives fluid from the vascular spaces into the surrounding retina,” according to Harvard researchers.
In a recent University of Pennsylvania study, scientists found that anemia was associated with an increased DME risk. The mechanism is unclear, although it’s likely that any condition that affects hemoglobin and oxygen levels in the blood (like anemia) will also have adverse effects on blood vessels. The good news: Anemia, like many of these risk factors, is treatable. If you have diabetes, talk with your doc about all the risks for DME, and if you’re concerned about your vision, it’s a good idea to have your eyes checked. Early is best when it comes to DME.
Diabetes, Diabetic Retinopathy, and DME Statistics: National Eye Institute. (2019). “Diabetic Retinopathy.” nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/diabetic-retinopathy
High Blood Pressure and DME: NIH: U.S. National Library of Medicine. (n.d.) “Retinal Vein Occlusion.” medlineplus.gov/ency/article/007330.htm
Hypoalbuminemia and DME: Digital Journal of Ophthalmology. (1997). “A Review of Diabetic Macular Edema.” djo.harvard.edu/site.php?url=/physicians/oa/387
DME and Vision Loss: NIH: U.S. National Library of Medicine. (n.d.) “Risk Factors Associated with Diabetic Macular Edema.” ncbi.nlm.nih.gov/pubmed/23380134
DME and Hypertension: University of Michigan Medicine: Kellogg Eye Center. (n.d.) “Diabetic Retinopathy.” umkelloggeye.org/conditions-treatments/diabetic-retinopathy
DME and Pregnancy: Centers for Disease Control and Prevention. (2019). “Gestational Diabetes.” cdc.gov/diabetes/basics/gestational.html
DME and Anemia: Eye. (2019). “Anaemia and the Risk of Progression From Non-Proliferative Diabetic Retinopathy to Vision Threatening Diabetic Retinopathy.” ncbi.nlm.nih.gov/pubmed/31586167