"The retina is like a sheet of cellophane attached to the entire back wall of the eye. The tears usually occur in the periphery where the gel may be tugging on it. If a tear occurs, then fluid inside the eye can travel through the tear and track between the retina and the back wall of the eye thereby separating the retina off the back wall of the eye. This is called a retina detachment. Wherever the retina is detached there is no vision. Since this usually occurs first in the periphery it may be experienced as a total loss of vision in the peripheral field of view as if a curtain is being pulled across the vision from the side and it may advance across the center of vision."