Reversed Image on Retina

Although you always see everything right side up and never get the impression that people are walking on the ceiling, the lens of your eye is actually focusing an upside-down image on your retina. This is due to the special properties of the lens, in relation to the size and shape of the eye. The upside-down image is what is transmitted to the visual centers of the brain through the optic nerve. The brain simply transposes the picture to make it conform to what it knows it should be seeing.