figure 5.20 Eye Light from the environment passes through a series of structures in the front of the eye: the cornea, pupil, and lens. Sensory receptors are in the eye’s retina. As you can see from the light bulb, images appear upside down (and left–right reversed) on the retina—yet you see them right side up (a). The size of the pupil opening is controlled by the iris (b).