Vein leakage is an eye condition that has numerous causes incuding
direct physical damage to the eye (i.e. trauma) or as a result of other underlying
medical conditions (e.g. diabetes).
The image below is a photograph of the back of the eye of a person with this condition
Digital Retinal Photography.
In this case, one of the major veins has leaked and the blood obscures the vision.
Some vision may return depending on severity and position.