E like eye

E as in Eyes

Your eyes are at work from the moment you wake up to the moment you close them to go to sleep.  They take in tons of information about the world around you — shapes, colors, movements, and more.  Then they send the information to your brain for processing so the brain knows what's going on outside of your body.

Big as a Ping Pong Ball

The eye is about as big as a Ping-Pong ball and sits in a little hollow area (the eye socket) in the skull.  The eyelid protects the front part of the eye.  The lid helps keep the eye clean and moist by opening and shutting several times a minute.  This is called blinking, and it's both a voluntary and involuntary action, meaning you can blink whenever you want to, but it also happens without you even thinking about it.

The eyelid also has great reflexes, which are automatic body responses, that protect the eye.  When you step into bright light, for example, the eyelids squeeze together tightly to protect your eyes until they can adjust to the light.

The white part of the eyeball is called the sclera.  The sclera is made of a tough material and has the important job of covering most of the eyeball.

The cornea, a transparent dome, sits in front of the colored part of the eye.  The cornea helps the eye focus as light makes its way through.  It is a very important part of the eye, but you can hardly see it because it's made of clear tissue.  Like clear glass, the cornea gives your eye a clear window to view the world through.

Iris Is The Colorful Part

Behind the cornea are the iris, the pupil, and the anterior chamber.  The iris is the colorful part of the eye. When we say a person has blue eyes, we really mean the person has blue irises!  The iris has muscles attached to it that change its shape.  This allows the iris to control how much light goes through the pupil .

The pupil is the black circle in the center of the iris, which is really an opening in the iris, and it lets light enter the eye.

The anterior chamber is the space between the cornea and the iris.  This space is filled with a special transparent fluid that nourishes the eye and keeps it health.

Light, Lens, Action!

Doctors use special microscopes to look at these inner parts of the eye, such as the lens.  The lens sits behind the iris and is clear and colorless.  The lens' job is to focus light rays on the back of the eyeball — a part called the retina.

Your retina is in the very back of the eye. It holds millions of cells that are sensitive to light.  The retina takes the light the eye receives and changes it into nerve signals so the brain can understand what the eye is seeing.

A Muscle Makes It Work

The lens is suspended in the eye by a bunch of fibers.  These fibers are attached to a muscle called the ciliary  muscle.  The ciliary muscle has the amazing job of changing the shape of the lens.  That's right — the lens actually changes shape right inside your eye!  Try looking away from your computer and focusing on something way across the room.  Even though you didn't feel a thing, the shape of your lenses changed.  When you look at things up close, the lens becomes thicker to focus the correct image onto the retina.  When you look at things far away, the lens becomes thinner.

The biggest part of the eye sits behind the lens and is called the vitreous  body.  The vitreous body forms two thirds of the eye's volume and gives the eye its shape. It's filled with a clear, jelly-like material called the vitreous humor.

Rods and Cones Process Light

The retina uses special cells called rods and cones to process light.  Just how many rods and cones does your retina have?  How about 120 million rods and 7 million cones — in each eye!

Rods see in black, white, and shades of gray and tell us the form or shape that something has.  Rods can't tell the difference between colors, but they are super-sensitive, allowing us to see when it's very dark.

Cones sense color and they need more light than rods to work well.  Cones are most helpful in normal or bright light.  The retina has three types of cones.  Each cone type is sensitive to one of three different colors — red, green, or blue — to help you see different ranges of color.  Together, these cones can sense combinations of light waves that enable our eyes to see millions of colors.

Helping You See It All

Rods and cones process the light to give you the total picture.  You're able to see that your friend has brown skin and is wearing a blue hat while he tosses an orange basketball.

Sometimes someone's eyeball shape makes it difficult for the cornea, lens, and retina to work perfectly as a team.  When this happens, some of what the person sees will be out of focus.

To correct this fuzzy vision, many people wear glasses.  Glasses help the eyes focus images correctly on the retina and allow someone to see clearly.  As adults get older, their eyes lose the ability to focus well and they often need glasses to see things up close or far away.

Have No Fear, You Have Tears

For crying out loud, the eye has its own special bathing system — tears!  Above the outer corner of each eye are the lacrimal  glands, which make tears.  Every time you blink your eye, a tiny bit of tear fluid comes out of your upper eyelid.  It helps wash away germs, dust, or other particles.

Your eyes sometimes make more tear fluid than normal to protect themselves.  This may have happened to you if you've been in a dusty or smoky area, or if you've been near someone who's cutting onions.

The eyes you have will be yours forever — treat them right and they'll never be out of sight!

NIMBLE  has a great variety of exercise to help and exercise your eyesight!