If your blood glucose stays high over time, it can damage the tiny blood vessels in the back of your eyes. This damage can begin during prediabetes, when blood glucose is higher than normal, but not high enough for you to be diagnosed with diabetes. Damaged blood vessels may leak fluid and cause swelling. New, weak blood vessels may also begin to grow. These blood vessels can bleed into the middle part of the eye, lead to scarring, or cause dangerously high pressure inside your eye.
Diabetic eye disease includes diabetic retinopathy, diabetic macular edema, cataracts, and glaucoma.
Over time, diabetes can cause damage to your eyes that can lead to poor vision or even blindness.