Damage to blood vessels in the retina is called diabetic retinopathy . When the blood vessels in the retina are damaged, they leak fluid or blood. The fluid and blood deposits in the retina, causing it to swell. If the swelling takes place in the center of the retina, vision becomes blurry or distorted. This is called macular edema .
Retinal ischemia occurs when small blood vessels, called capillaries, close.
Vision is blurred because the retina no longer has enough blood supply to function properly. The eye forms new, fragile blood vessels in an effort to get enough blood to the retina. These new vessels tend to break and bleed into the vitreous, the clear jelly-like substance that fills the center of the eye. Vitreous hemorrhage can be mild, producing a few dark floaters, or it can be severe, causing a total loss of vision. Vision loss from diabetic retinopathy is largely preventable.