Cystoid macular edema (CME) is a condition that happens when blood vessels in your retina leak fluid into a part of your eye called the macula. This can cause a buildup of fluid leading your macula to swell. Swelling due to fluid buildup is called edema.

Your macula is a part of your retina, which is a layer of tissue at the back of your eye. It’s the part of your eye that helps you see color and fine detail.

Macular edema can cause blurry vision and changes to how you see colors — over time, it can even lead to central vision loss. Central vision is what you can see when looking straight ahead.

The most common causes of macular edema are diabetic retinopathy and age-related macular degeneration (AMD). Read on to learn more about the mechanisms behind macular edema, its symptoms, and what treatments are available.

Macular edema happens when fluid leaks into your macula and causes it to swell. The fluid typically comes from damaged blood vessels in your retina.

These damaged blood vessels can occur due to several factors, including:

  • Diabetes. Diabetic macular edema (DME) is a complication of diabetes and the most common cause of vision issues for adults under 65 years old. DME results from a diabetes-related eye disease called diabetic retinopathy. High blood sugar can increase someone’s chances of developing diabetic retinopathy and cause damage to the blood vessels in your retina.
  • Eye surgery. Your risk for macular edema increases after any type of eye surgery, including surgery for glaucoma, cataracts, or retinal disease. Macular edema that occurs after eye surgery is normally mild and temporary.
  • Age-related macular degeneration (AMD). AMD is a common eye condition that causes central vision loss. One type of AMD, wet AMD, is caused by a growth of abnormal blood vessels in your retina that then leak into your macula and cause damage. This can also cause macular edema.
  • Blocked retinal blood vessels. Inflammation, atherosclerosis, high blood pressure, glaucoma, or other conditions can sometimes block retinal blood vessels. When this happens, blood doesn’t drain correctly and can leak into your retina. That fluid can then leak into your macula and cause macular edema.
  • Swelling in your retina. Multiple inflammatory diseases can lead to swelling of your retina and macula. These diseases can break down your macula tissue and lead to eye damage.
  • Aging. As your eye ages, the gel between your eye lens and retina — called the vitreous — begins to detach. Sometimes, it doesn’t detach fully and will pull on the macula. This can lead to swelling and scar tissue.
  • Genetic conditions. Some genetic conditions, such as retinoschisis, can cause macular edema.
  • Eye tumors. Both cancerous and benign eye tumors can cause macular edema.
  • Eye injuries. An injury to your eye can lead to macular edema.

Macular edema generally doesn’t cause any pain.

At first, you might not notice symptoms of vision changes. But when symptoms do occur, they often include:

If you notice any of these symptoms, you should see an eye doctor. Some of these symptoms may occur with other conditions but macular edema can cause significant vision loss or even blindness without treatment.

An eye doctor will likely perform a series of tests to confirm a diagnosis of macular edema. They will often begin with a thorough eye exam and discuss your health history.

After that, they may perform several tests, including:

  • Visual acuity. A visual acuity test involves reading an eye chart. You’ll read letters of various sizes to test the strength of your vision.
  • Dilated eye exam. A dilated eye exam is done using special eye drops that widen your pupils. This allows an eye doctor to see your retina more clearly.
  • Amsler grid. An Amsler grid is a visual test where you look at a grid and say whether you see the lines of the grid as straight or wavy.
  • Fluorescein angiogram. This test is performed by injecting a dye into your arm. The dye travels through your blood vessels and helps highlight damaged blood vessels in your eye. A camera is then used to take pictures of your eye and the highlighted blood vessels.
  • Optical coherence tomography. This test uses a specialized light and camera to take detailed images of the cellular layers of your retina.

The right treatment for your macular edema depends on the underlying cause and on the extent of the damage.

When caused by injury or surgery, macular edema can be temporary and might even resolve on its own.

If the cause is diabetes or inflammatory eye conditions, macular edema is progressive and needs prompt treatment. In these cases, vision loss caused by macular edema can be reversed if it’s caught early. But treatment can stop the progression of macular edema before vision loss becomes significant.

People with diabetes and others with an increased risk of macular edema should get regular dilated eye exams. This helps doctors spot the condition early on, while it’s more manageable and even reversible.

Common treatments include:

  • Anti-VEGF injections. Anti-VEGF injections are the most common treatment for macular edema. These treatments stop the growth of blood vessels in your eyes. This slows down macular edema and prevents further damage.
  • Anti-inflammatory treatments. Anti-inflammatory treatments can reduce swelling in the eye caused by inflammatory eye disease. Corticosteroids in the form of eye drops, pills, or injections are the most common anti-inflammatories used for macular edema.
  • Vitrectomy. A vitrectomy can be performed when macular edema is caused by the vitreous tugging on the macula. This surgical procedure removes the vitreous so that it’s no longer straining the macula.

A variety of conditions and factors can cause macula edema, including diabetes, inflammatory eye conditions, AMD, and eye aging. The cause of your macular edema will determine the most effective treatment options for you.

Any vision loss caused by macular edema can be reversed when it’s caught early, which is why it’s important to see an eye doctor for any unusual eye symptoms. Early treatment can keep vision loss to a minimum and prevent further damage from happening.