Your eyes are one of the most important ways you sense the world around you. Without your having to think about it, these amazing organs make sense of the beams of light that bounce off objects and into your eyes. Your eyes then tell your brain about the colors, shapes and movements you are seeing, all within split seconds. You can only see a portion of your eye, but altogether it is about the size of a ping pong ball, according to the website Kids Health.
Iris and Pupil
Your eye color is determined by the color of your iris---you may have blue, brown or green irises, or one of many shades in between these colors. In the center of the iris is a black-colored opening called the pupil, which determines the amount of light coming into the eye. The pupil constricts, or grows smaller, in bright light, and opens wider when there is less light.
Cornea and Anterior Chamber
Even though it is visible, you may not be aware of the cornea, because this part of the eye is transparent and serves as a kind of window, according to the Pasadena Eye website.This dome of clear tissue covers the iris and pupil and helps the eye focus. Between the cornea and iris is a space called the anterior chamber, filled with a transparent fluid necessary for eye health.
Sclera
The sclera is the white part of the eye. Although you only notice the small white part that is outside the iris, the sclera actually covers most of the eyeball, even the parts you don't see. You may sometimes notice tiny red lines in the whites of your eyes---these are blood vessels that nourish the sclera.
Lens, Retina and Optic Nerve
After light enters the pupil, it reaches the lens, which is located behind the iris. The lens, controlled by the ciliary muscle, serves to focus light onto the retina at the back of the eye. The retina, filled with millions of special cells called rod and cones, translates light into nerve signals and sends them to the brain via the optic nerve, which acts as a messenger between the eye and the brain.
Vitreous Body
Sitting behind the eye's lens is the vitreous body, which gives shape to the eye and makes up 2/3 of its volume. It consists of a clear jelly-like liquid called the vitreous humor.
Lids, Lashes and Tear Glands
Your eye has built-in safeguards that protect the delicate system that gives you vision. The lacrimal glands make tears, which bathe the eye with fluid. Each time you blink, a bit of tear fluid is released from your upper eyelid, helping to keep your eyes from drying out and also washing away any dust or germs. The fluid drains into the lacrimal or tear duct at the inside corner of your eye. Your eyelids allow you to shut out light when you are sleeping and close quickly if something is about to hit your eye; the lashes serve to trap dust or debris.
