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. In addition, your eyelids involuntarily open and close (blink) every few seconds. During each blink, fluid produced by tear glands passes over the cornea and lubricates the surface of each eye. This helps keep your eyes moist and washes away germs, dust and stray eyelashes.
The front of your eye has three major parts, including the:
A thin transparent tissue called the conjunctiva covers the sclera. Blood vessels visible in the white part of your eye are located within the conjunctiva.
Behind the scenes, other parts of your eye work to help you see, including the:
Structures at the back of your eye include the:
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 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.