Your eyes and your brain work together to see. Your eyes use special nerves to send what you see to your brain, so your brain can process and recognize what you’re seeing. In eyes that work correctly, this process happens almost instantly. When this doesn’t work the way it should, a person may be visually impaired, or blind. The problem may affect one eye or both eyes. When you think of being blind, you might imagine total darkness. But most people who are blind can still see a little light or shadows. They just can’t see things clearly. People who have some sight, but still need a lot of help, are sometimes called legally blind.