Iris
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina.
Introduction to the Eye
The eye is a complex optical system which collects light from the surrounding environment; regulates its intensity through a diaphragm; focuses it through an adjustable assembly of lenses to form an image; converts this image into a set of electrical signals; and transmits these signals to the brain, through complex neural pathways that connect the eye, via the optic nerve, to the visual cortex and other areas of the brain.
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber.
Optic Nerve
The optic nerve, also called cranial nerve II, transmits visual information from the retina to the brain.