The retina is a thin sheet of nerve tissue in the back of the eye where light rays are focused and transmitted to the brain. The vitreous is a gel-like substance that fills the eye and is connected to the retina, optic nerve and many blood vessels. Problems with the retina and vitreous -- including retinal tear, retinal detachment, severe intraocular infection (endophthalmitis) and trauma -- can lead to vision loss and even blindness. Surgery can correct problems before vision is lost or prevent further deterioration from occurring.