1. Why do you think you have eyebrows?
What do you think your eyelids and
eyelashes do?
Take a guess at how many times the
average person blinks a day!

2. How do we see?
Eye is about as big as a ping pong ball. Sits in the eye socket which is a hollow socket in the skull. Has more than 2 million working parts. We are born with the size eye we have now! The white part of the eyeball is called the sclera- very tough material. It has tiny blood vessels that deliver blood to the sclera.

3. A transparent tissue covering the front of the eye.
cornea
Cornea – transparent dome is in front of the colored part of the eye. Helps the eye focus as light makes it way through.
A transparent tissue covering the front of the eye.

4. Hole allows light to pass through
pupil
Pupil is the black circle in the center of the eye. Its really just an opening which lets light enter.
cornea
Hole allows light to pass through

5. Muscle that controls the size of the pupil
iris
The iris is the colorful part of the eye. It has muscles attached to it that change its shape so it can control how much light goes through the pupil.
under
dim light
under
bright light

6. Thick in middle, transparent and elastic . The lens focuses images.
pupil
After light enters the pupil it hits the lens. It is clear and colorless and its job is to focus light rays on the back of the eyeball. It is similar to the lens of a movie projector at the movies.
cornea

7. Distant object Near object - Focusing muscles contract
- Focusing muscles relax
- Lens becomes thicker
- Lens becomes thinner

8. lens pupil cornea Vitreous humor
The biggest part of the eye sits behind the lens and is called the vitreous humor. It gives the eye its shape.
cornea
Clear jelly-like fluid that helps to maintain the eyes shape
Vitreous humor

9. Contains receptors that respond to the light
lens
retina
pupil
The back of the eyeball is called the retina. It holds millions of cells that are sensitive to light. The retina takes the light the eye recieves and changes it into electrical signals so the brain can understand what the eye is seeing.
cornea
Vitreous humor

10. cones rods There are two types of light-sensitive cells on the retina:
Photoreceptors are rods and cones. We have about 120 million rods and 7 million cones in each eye. Rods see in black and white and shades of grey and tell us the shape of something. Allow us to see when it is very dark. Cones sense color. Three types of cones and each is sensitive to one of three different colors. They work together to sense combinations oflight waves that enable us to see millions of colors.

11. Transmits information from the retina to the brain
lens
retina
pupil
Optic nerve is the great messenger in the back of the eye. The rods and cones change the colors and shapes into millions of electrical nerve messages and the nerve carries them from the eye to the brain- like a high speed telephone line! The image on your retina is actually upside down but the brain knows how to flip flop the image.
cornea
optic nerve
Vitreous humor