Animal eyes, including yours, have one important job in common, and that’s to collect light so they can see.
No animal can see in total darkness—not even a cat, as some people mistakenly believe.
Animal eyes have many of the same basic parts for collecting light. First, they need a pupil, or a hole to let in the light, and they also need a lens to focus that light. Without a lens, images would be very fuzzy. Finally, eyes have a retina (RET-ih-na)—which is sort of like a movie screen—where the light is projected. Chemicals in the retina change the light images into nerve signals that the brain can understand.
We know what parts animal eyes have in common, but what makes them different from each other?
