Good morning everyone! Today we are going on a field trip to the Anatomy Museum.

Wow Ms. Frizzle, is this going to be a normal field trip?

Well Arnold, the class is actually going to be learning about the anatomy of the eye... by entering YOUR eye!

Oh no..

First, the Magic School Bus enters the eye through the cornea, which is the outer layer of the eye

The cornea focuses light and protects the eye!

cornea ---->

The iris is the colored ring in the eye. It is a muscle that contracts to control how much light enters eye through the pupil.

The iris contracts to allow the magic school bus to enter!

The pupil is the hole in the center of the iris which allows light to enter the eye.

iris ---------------->

Next, the bus enters the lens!

The lens' job is to 

focus the light and 

image onto the 

retina. The image 

seen is flipped

upside down and 

projected onto the

retina.

<------ lens

After passing through the lens, the bus moves to the retina at the back of the eye.

The retina contains visual receptors called rods and cones which allow us to see colors and in darkness!

The fovea is central point of focus in the retina. This is where the majority of our cones are.

This is what the retina looks like up close!

This is where the rods (which allow us to see in low light) and cones (which allow us to see in color) are. 

Ms. Frizzle, what would happen if we didn't have any cones?

Great question Phoebe! If we didn't have cones, we wouldn't be able to see any colors. In fact, Arnold seems to be missing his red cone! This means he's partially colorblind and has difficulty seeing the color red!

Most people who are colorblind are red-green colorblind, meaning the cones which let then see 

those colors are weak or missing. Some 

people even have complete color 

blindness and can only see in black and 

white! This is called Achromatopsia, and 

is VERY rare.