DME starts when your blood sugar isn't well controlled. Consistently high blood sugar harms blood vessels throughout your body, like in your heart, as well as the small blood vessels in your retina -- the tissue at the back of your eye that sends images to your brain.
Without healthy blood vessels, your retina can't work the way it's supposed to.
Your body tries to help out by making more of a protein called vascular endothelial growth factor, or VEGF. But too much of it weakens those blood vessels. In time, they can tear and leak blood and fluid into your retina. Your retina will swell and get thicker, a condition called diabetic retinopathy. The leaking fluid also causes swelling in the macula, the place in the center of the retina that gives you sharp, clear vision.
Diabetes is the main cause of macular edema. But it can happen for other reasons, too, including cataract surgery or other operations on your eyes, macular degeneration, swelling in the uvea (the middle part of your eye), and blocked veins in your retina or damage from radiation.
Who Gets It?
Your chances of DME go up when:
You're more likely to get DME if you:
Types of DME
There are two main ones:
- Focal DME is small spots of fluid leaking.
- Diffuse DME has leaks and swelling throughout your macula.
Your eyesight may be worse with diffuse DME.
You could have DME and not know it because it doesn't hurt, and your vision may change so slightly or slowly that you don't realize it's happening.
The macula is the part of your eye where light gets focused, like a movie screen. The extra fluid and swelling in your macula distort that surface, and things look wavy or blurry. It may be harder to recognize a friend's face, read, watch TV, and drive.
You might not notice this if you have DME in just one eye.
Your macula is also key for seeing in color. DME can make colors look faded or washed out.