We use vision for almost everything in our lives, but have we really thought about how we see things. First there has to be light to see things. The cornea is the part of the eye that bends and focuses the light before it enters our eyes. The next part is it has to go through the lens of the eye, which is behind the pupil. From there the light travels to the vitreous body. After that it finds its ways to the retina, which is the light-sensitive membrane on which images are cast by the cornea. They names of the light sensitive cells are rods and cones. The rods let us see in dim light. Cones let us see bright light and color. Light stimulates rods and cones in the retina, and a nerve impulse is transmitted to the brain through the optic nerve. Then you can see. You can also test the sharpness of your eye by reading an eye chart from a certain distance.