Diabetic retinopathy occurs when elevated sugar in the blood causes damage to blood vessels in the body over time, known generally as diabetic retinopathy. With progressive damage, the blood vessel shape and integrity can become altered. In one common situation, the blood vessels become leaky and cause swelling in the retina. This is known medically as macular edema and can be treated with a combination of lasers and intravitreal injections (medications injected into the eye). Another type of blood vessel abnormality in diabetes occurs when the blood vessels become closed down. Areas of the eye supplied by these non-functioning blood vessels become ischemic, meaning they are starved for nutrients and oxygen, and they then stimulate the production of new blood vessels, which can bleed or tug on vital structures. This is known medically as proliferative diabetic retinopathy, and it can be treated with lasers to areas of ischemic tissue. Sometimes bleeding or tugging from new blood vessels can require surgery to clear the blood or release traction.