The eye is a complex organ that directly influences the way a person interacts with the world. Light waves are received through the cornea where they are bent, refracted and focused by the cornea, lens and vitreous. The light rays come to a sharp focus on the retina, resulting in an upside-down image. The light rays are converted to electrical impulses that travel a pathway along the optic nerve through the thalamus to the back of the brain, where they register on the primary visual cortex. From there, visual impulses reach out to other parts of the brain, creating an instantaneous mental image of a colorful, three-dimensional world perceived in an upright position.

The eye is composed of many small parts, each vital to normal vision. The ability to see clearly depends on how well these parts function and work together. Here are the principle components parts of the eye:

Cornea. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber and provides most of an eye's optical power. Light passes through the cornea and as it passes through, is focused so we can see.

Pupil. The pupil is variable-sized black circular opening in the center of the iris that regulates the amount of light that enters the eye.

Lens. The lens is a transparent, biconvex intraocular tissue that helps bring rays of light to a focus on the retina.

Iris. The iris is pigmented tissue lying behind the cornea that gives color to the eye (e.g., blue eyes) and controls amount of light entering the eye by varying the size of the pupillary opening.

Sclera. The sclera is the opaque, fibrous, protective outer layer of the eye ("white of the eye") that is directly continuous with the cornea in front and with the sheath covering optic nerve behind.

Endothelium. A single layer of cells which line the posterior surface of the cornea.

Descemet's Membrane. A transparent, highly elastic apparently structureless membrane that covers the posterior surface of the cornea and is lined with endothelium.

Stroma. The stroma is regularly arranged collagen fibers in the cornea that comprises 90% of the cornea’s thickness.

Bowman's Membrane. The thin outer layer of the substantia propria of the cornea, immediately underlying the epithelium

Epithelium. Amembranous cellular tissue that covers the anterior surface of the cornea

For a comprehensive look at the anatomy of the eye and a complete glossary of ocular terms, go here.