The science of vision seems like magic in and of itself. To think a tiny little 1-inch-diameter (2.54 centimeter) organ is responsible for our being able to see the world around us -- all of its color, light and depth. To achieve this miracle of sight, light enters the eye through the cornea and makes its way to the back to the retina, located in the middle of the eye. Within the retina are a variety of rod cells and cone cells that are responsible for seeing color and detail. The retina also contains something known as visual purple, or rhodopsin for those science buffs out there. It is this chemical that takes the messages from the eye and translates them into electrical impulses for the brain to interpret [source: Bianco]. If it weren't for the brain, vision would not be possible either. In fact, it is the brain that is key to 3-D vision, not the eye.
Because we all have two eyes that are set apart, each eye takes in a slightly different view of the world. Have you ever taken your 3-D glasses off during a movie? That slightly blurred image that looks like layers of the same image that haven't quite been lined up properly is how your eyes see the world. However, once these images are turned into electrical impulses for the brain to interpret, the brain creates the illusion of depth and stereoscopic, or three-dimensional, vision.
So what does the science of vision have to do with eye puzzles? Ever since the discovery of stereoscopic vision, scientists have been trying to create the illusion of 3-D from flat objects based on the way the eyes and brain create depth in our three-dimensional world. We'll dive further into the history of 3-D vision and autostereograms on the next page.