The eye is an organ. Behind its visible portions is a complicated array of delicate mechanisms that work in unison to transmit an image to the brain.
Vision, ability to see the features of objects we look at, such as color, shape, size, details, depth, and contrast. Vision is achieved when the eyes and brain work together to form pictures of the world around us. Vision begins with light rays bouncing off the surface of objects. These reflected light rays enter the eye and are transformed into electrical signals. Millions of signals per second leave the eye via the optic nerve and travel to the visual area of the brain. Brain cells then decode the signals into images, providing us with sight.
Almost all animals respond to light. The one-celled amoeba responds to light by turning in its direction. Bees have complicated eyes that contain many lenses for sensing colors and shapes of flowers. However, it is the vertebrates (animals with backbones) that have eyes and a brain that work together to process light into true images. Human vision is particularly unique in that the human brain can process visual images and use them to create language and pictures and to store information for future use.
The eyes of many vertebrates are specialized for certain situations. Bats see best at night. Birds of prey, such as hawks and eagles, are able to see extremely small details, such as tiny rodents viewed from high in the air.