The Max Planck Institute for Biological Cybernetics in Tübingen has done a study on how rats see, and it turns out they see things very differently than we do. I have seen websites that try to mimic the way rats perceive the world, as they are believed to have poor eyesight. However, the quality of their vision is not the only difference in what they see. While human beings have stereoscopic vision, with both eyes looking at the same point and combining the image into one picture, a rat's eyes move in different directions independently of each other and thus they have two different field of views. The way their eyes move provides them with a constant view of what is above them - most likely a defense mechanism to protect them from birds of prey.
For more information, check out the article Rats Have a Double View of the World from Science Daily.