The eye is the organ of sight. Eye pain can be cause by conditions involving the eyeball (orbit) or be caused by conditions of structures around the eye.

The eye has a number of components. These components include but are not limited to the cornea, iris, pupil, lens, retina, macula, optic nerve, choroid and vitreous.

The cornea is the clear front window of the eye that transmits and focuses light into the eye.

The iris is the colored part of the eye that helps regulate the amount of light that enters the eye.

The pupil is the dark aperture in the iris that determines how much light is let into the eye.

The lens is the transparent structure inside the eye that focuses light rays onto the retina.

The retina is the nerve layer that lines the back of the eye, senses light and creates impulses that travel through the optic nerve to the brain.

The macula is a small area in the retina that contains special light-sensitive cells and allows us to see fine details clearly.

The optic nerve is the nerve that connects the eye to the brain and carries the impulses formed by the retina to the visual cortex of the brain.

The choroid is a thin vascular layer between the sclera and the retina that supplies blood to the retina and conducts arteries and nerves to other structures in the eye.

The vitreous humor is a clear, jelly-like substance that fills the middle of the eye.

Medical terms for pain in the eye are ophthalmalgia and ophthalmodynia.

Source: http://www.rxlist.com