Your eyes are your windows to the world — but they need to be shielded from the elements to keep you seeing clearly.
Upper and lower eyelids protect the front of your eyeballs by blocking foreign objects and bright light. Your eyelids also involuntarily open and close (blink) every few seconds when you're awake.
One of the muscles involved in blinking is called the orbicularis oculi. During each blink, fluid produced by tear (lacrimal) glands passes over the protective dome of clear tissue at the front of your eyes (cornea) and lubricates the surface of the eyes.
Fluid drains out of the eye through the lacrimal ducts. This process helps keep your eyes moist and washes away germs, dust and stray eyelashes.
The front of your eye has major parts:
Behind the scenes, other parts of your eye work to help you see:
Structures at the back of your eye:
Each eyeball has six muscles attached to the sclera — the white part of your eye. These muscles, five of which are shown above, allow you to move your eye and track an object without turning your head. The eye muscles also allow you to shift your field of gaze left, right, up, down and diagonally. Your brain coordinates these eye movements so that both eyes can move together when tracking an object.