The pupil is centrally located in the iris, or the colored part of the eye. This is the muscle responsible for constricting and dilating the pupil to control the amount of light which enters the eye. The pupil constricts when an environment is well lighted, or when focusing on objects close to the eye. It dilates when we are in an environment that is poorly lit, or to focus on objects in the distance. Behind these structures lie the lens, the retina, the macula, and finally the optic disc in the very posterior portion of the eye. The lens is the refracting medium within the eye, keeping objects in continual focus on the retina. The retina is the receptive layer of the eye where the light waves are localized and transmitted into nerve impulses where they form the optic disc. The macula is located on the retina and is responsible for our central field of vision (Jarvis, 2012, p. 282). Additional structures outside of the ball of the eye, but still essential to maintaining its full functionality include the optic nerve, optic tract, and occipital lobe of the brain. These all run from the back of the eye through to the most posterior (back) part of the brain (Montgomery, 2014). .
More than half of our neocortex, or the "wormy" lobe part of the brain, is dedicated to processing visual information sent by our eyes. A huge misconception is that we see images with our eyes. The eye only processes the light that an object reflects or emits (Jarvis, 2012, p. 279, 283). Therefore, the eye cannot detect objects when light is totally absent. When the light is reflected it passes the cornea, through the pupil, then the lens. At this point, the light pattern being reflected turns both backwards and upside-down. The light continues to travel, passing through the liquid vitreous humor; which is the clear gel that constitutes approximately 80% of the eyes volume, and landing on the retina (Montgomery, 2014).