How the eyes works, using the terms cornea, pupil, iris, retina, and optical nerve?

Light initially enters the eye through the cornea, it protects the eye and helps to focus light rays into the retina at the back of the eye. The passage of light continues through the pupil which looks like a black circle in the centre of the eye. The pupil is not a structure itself but helps to control the amount of light entering the eye. The iris surrounds the pupil, is the coloured part of the eye. It is a ring of muscles which expand or contract to change the size of the pupil and control the amount of light. The optic nerve carries the visual information from the retina to the primary visual cortex. The optic nerve exits the eye at the back of the retina, the same point where blood vessels enter and exit the eye.