Diabetic retinopathy (pronounced: Die-uh-BET-ik Ret-ih-NOP-uh-thee) is when the back of the eye, known as the retina, is damaged by diabetes.
When a person has diabetes, it is possible for the blood vessels in the eye to break and leak out blood/fluid into the eye, which can cause many problems, depending on the severity of the disease. Since these vessels are in the back of the eye were you cannot see them, people are unaware that they have broken.