INTRODUCTION:
The orbit is the bony cavity that contains the eyeball, muscles, nerves, and blood vessels, as well as the structures that produce and drain tears. Each orbit is a pear-shaped structure that is formed by several bones.

STRUCTURE
• Anterior chamber- The region of the eye between the cornea and the lens that contains aqueous humor.
• Aqueous humor- The fluid produced in the eye.
• Ciliary body-Part of the eye, above the lens, that produces the aqueous humor.
• Choroid – Layer of the eye behind the retina, contains blood vessels that nourish the retina.
• Cones- The photoreceptor nerve cells present in the macula and concentrated in the fovea (the very center of the macula); enable people to see fine detail and color.
• Cornea- It is the outer, transparent structure at the front of the eye that covers the iris, pupil and anterior chamber; it is the eye’s primary light-focusing structure.
• Iris- The colored ring of tissue behind the cornea that regulates the amount of light entering the eye by adjusting the size of the pupil.
• Lens- The transparent structure suspended behind the iris that helps to focus light on the retina; it primarly provides a fine-tuning adjustment to the primary focusing structure of the eye, which is the cornea.
• Macula- The portion of the eye at the center of the retina that processes sharp, clear straight-ahead vision.
• Optic nerve- The bundle of nerve fibers at the back of the eye that carry visual messages from the retina to the brain.
• Photoreceptors- The light sensing nerve cells (rods and cones) located in the retina.
• Pupil- The adjustable opening at the center of the iris through which light enters the eye.
• Retina- The light sensitive layer of tissue that lines the back of the eye.
• Rods- Photoreceptor nerve cells in the eyes that are sensitive to low light levels and are present in the pupil, but outside the macula.
• Sclera- The tough outer coat that protects the entire eyeball.
• Vitreous- Clear jelly-like substance that fills the eye from the lens to the back of the eye.