Text referring to the dog reads: 1, light waves bouncing off an object enter your eye through the cornea, pupil, and lens. The dark shaded rounded structure in the center of the eye is labeled pupil. A thin circular structure surrounding the pupil is labeled iris. Text referring to the Iris label reads: 2, Iris dilates and contracts pupil to control amount of light entering eye. A transparent front part that covers iris, pupil, and anterior chamber is labeled cornea. Text referring to the eye in general reads: 3, cornea and lens focus light waves toward the retina, bending the light and projecting an inverted image. A circular structure labeled lens is situated directly behind the iris and the pupil. The inner surface of the eye is lined by retina. A circular structure located in the back of the eye is labeled optic disc. The optic nerve connects the center of the eye to the optic disc and thereafter to the brain at the posterior part of the eye. A tiny pit below the optic disc in the back of the eye is labeled fovea. The fovea shows the inverted image of the dog.
An enlarged section of retina shows the passage of light rays through different cells. Text referring to the light label reads: 4, light strikes the retina, exciting photoreceptors. The retina shows 3 types of spindle shaped cells labeled ganglion cells, bipolar cells, and photoreceptors. The photoreceptors show rod cells and cone cells. An arrow from photoreceptors moves through bipolar cells and ganglion cells and shows a direction toward back of the eye. Text referring to the retina in general reads: 5, in the retina, rods and cones fire, activating bipolar cells, whose axons form the optic nerve carrying messages to the brain.