Cornea	The clear outer part of the eye’s focusing system located at the front of the eye.
Pupil	The opening at the center of the iris. The iris adjusts the size of the pupil and controls the amount of light that can enter the eye.
Iris	The iris is a diaphragm of variable size whose function is to adjust the size of the pupil to regulate the amount of light admitted into the eye. It is the colored part of the eye.
Lens	A clear part of the eye behind the iris that helps to focus light, or an image, on the retina.
Vitreous	A clear gel that fills the inside of the eye.
Retina	The light-sensitive tissue lining at the back of the eye. The retina converts light into electrical impulses that are sent to the brain through the optic nerve.
Macula	The small sensitive area of the retina that gives central vision. It is located in the center of the retina and contains the fovea.
Optic nerve	A bundle of more than one million nerve fibers that carries visual messages from the retina to the brain.
Sclera	It is a tough white sheath around the outside of the eye-ball.
Ciliary body	The ciliary muscle is a ring-shaped muscle attached to the iris. It is important because contraction and relaxation of the ciliary muscle controls the shape of the lens and hence focusing power will be changed.
Choroid	The structure of the choroid itself consists mainly of a dense capillary plexus and of many arterioles and venules transporting blood to and from this plexus. It contains pigment that absorbs excess light.