Tour of the Eye
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How Does the Eye Work?


The eye is an organ with several parts. These parts work together to perform the eye's primary function: to detect light. This page features information about these parts and how they can impact vision.


Eyelid: The eyelid protects the eye and keeps it clean by blinking. Eyelid glands secrete oil, water and other substances that coat the eye with "tear film."  With unhealthy glands, the tear film is missing components and the eye  may feel uncomfortable and have excess tearing. Even with the added tears, the eye will feel dry and scratchy.  Treatments for this condition include using warm compresses or artificial tears. It is best to use artificial tears that are not labeled as "taking the red out."

Sclera:The white part of the eyeball is called the sclera and covers most of the eyeball.

Cornea: The cornea is the clear outer part of the eye located at the front of the eye. It does most of the eye's focusing.The cornea's cells  continuously pump water. If those cells become damaged, the cornea will become swollen and cloudy and a transplant is needed. Corneal transplants are successful because the cornea has no blood vessels. However, there is a constant need for organ donors to provide corneas.

Iris: The iris is the ring-shaped colored part of the eye behind the cornea. It regulates how much light enters the eye.

Pupil: The pupil is the opening at the center of the iris. The iris' muscles change the iris' width which changes the pupil's size. This is how the iris controls how much light can enter the eye.

Lens:The lens helps to focus light onto the retina. A cloudy lens is called a "cataract." Cataract surgery can be done when a person notices that his or her vision is inadequate. The surgeon makes a tiny incision and inserts a long, thin instrument that breaks up the cloudy lens with ultrasound waves and suctions the pieces out of the eye. A clear plastic lens is then placed in the eye. The incision is so small that stitches usually are not needed.

Retina: The retina is tissue that covers the eye's inside surface. It converts light into electrical impulses that are sent to the brain through the optic nerve fibers. Diabetes can cause growth of abnormal blood vessels on the retina's surface. These blood vessels can leak and bleed, and over time they may contract and detach the retina. Diabetes also can cause swelling of the retina. A person with diabetes should have an annual eye exam to check for abnormal blood vessels and retinal swelling. These problems are treated most easily and most effectively when caught early. The best way to prevent vision problems from diabetes is to keep the blood sugar at a healthy level.

Vitrious Gel: The vitreous gel is a clear gel that fills the inside of the eye.

Macula: The macula is a small area of the retina at the center of the back of the eye. It provides central vision. At the center of the macula is the fovea, which allows one to see details sharply. Age-Related Degeneration affects the macula in a dry or wet form. can take In the wet form there is growth of abnormal blood vessels, and the dry form can convert to the wet form.