Macular edema is the build-up of fluid in the macula, an area in the center of the retina. The retina is the light-sensitive tissue at the back of the eye and the macula is the part of the retina responsible for sharp, straight-ahead vision. Fluid buildup causes the macula to swell and thicken, which distorts vision.

What causes macular edema?

Macular edema occurs when there is abnormal leakage and accumulation of fluid in the macula from damaged blood vessels in the nearby retina. A common cause of macular edema is diabetic retinopathy, a disease that can happen to people with diabetes. Macular edema can also occur after eye surgery, in association with age-related macular degeneration, or as a consequence of inflammatory diseases that affect the eye. Any disease that damages blood vessels in the retina can cause macular edema.

Structures of the Eye (suggested illustration)

What are the symptoms of macular edema?

The primary symptom of macular edema is blurry or wavy vision near or in the center of your field of vision. Colors might also appear washed out or faded. Most people with macular edema will have symptoms that range from slightly blurry vision to noticeable vision loss. If only one eye is affected, you may not notice your vision is blurry until the condition is well-advanced.

Diabetic macular edema (DME)

Diabetic macular edema (DME) is caused by a complication of diabetes called diabetic retinopathy. Diabetic retinopathy is the most common diabetic eye disease and the leading cause of irreversible blindness in working age Americans. Diabetic retinopathy usually affects both eyes.

Diabetic retinopathy is caused by ongoing damage to the small blood vessels of the retina. The leakage of fluid into the retina may lead to swelling of the surrounding tissue, including the macula.

DME is the most common cause of vision loss in people with diabetic retinopathy. Poor blood sugar control and additional medical conditions, such as high blood pressure, increase the risk of blindness for people with DME. DME can occur at any stage of diabetic retinopathy, although it is more likely to occur later as the disease goes on.

Experts estimate that approximately 7.7 million Americans have diabetic retinopathy and of those, about 750,000 also have DME. A recent study suggests that non-Hispanic African Americans are three times more likely to develop DME than non-Hispanic whites, most likely due to the higher incidence of diabetes in the African American population.

Courtesy: National Eye Institute, National Institutes of Health (NEI/NIH).