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 and detachment, macular degeneration, diabetic retinopathy, infection and trauma — can lead to vision loss and blindness. Early detection and treatment are critical in correcting problems before vision is lost and preventing further deterioration from occurring.