Rod+Cells+-+SMB

=Introduction= toc The eye is 0.9 inch in diameter. It is not perfectly round, it is slightly flattened in the front and back. The eyeconsists of three layers, the sclera, the choroid, and the retina. Without the eye the world around you would be left unseen. In this teeny tiny circular ball, is millions of rod and cone cells. in each eye there are 126 million rod cells and 6 million cone cells.

What are the layers of the eye?
The retina is the innermost layer of the eye. The retina is a thin, delicate, sensory tissue composed of layers of light sensitive nerves.The retina begins at the ciliary body and encircles the entire interior. The choroid is a thin **membrane** lying underneath the sclera. The choroid is composed of a dense pigment and numerous blood vessels that nourish the internal tissues of the eye. The sclera is the outer fibrous(define) layer.It encases and protects the eye. The piece of the sclera visible is the white of the eye. When the sclera is irritated it is know as a “bloodshot eye”. A “bloodshot eye is when your the sclera is irritated, the color is of the sclera is a brighter red color.

**Diseases**
Farsightedness is when you can see things that are far away but objects up close are blurry. The cause can be that the eyeball is to short or the lens is to weak. Nearsightedness is when you can see objects up close but you see objects that are far away are blurry.
 * Farsightedness ** and **nearsightedness** are common vision disorders. They occur because of a defect in the shape of the eye.
 * Glaucoma** is a serious vision disorder caused by a buildup of aqueous humor. The amount of fluid causes pressure up against the retina, affecting your sight. If untreated glaucoma will result in permanent blindness.

What is the job of rod cells?

 * Rods**, nerve cells of the retina, convert light first to **chemical energy** then to electrical energy. Rods can not detect color, but they are the first cells to detect movement. Rods function well in a dim lighted environment. These are the cells that allow us to see the stars.

Why do rods not see red?
Rods see mostly blue. They do not respond the red light. They dont respond to red light because they only see in black and white. Its the cones job to see the color. If you go without rod cell or cone cells you will be color blind.

What is the job of the cone cells?
in each eye there are about 126 mill ion rods and 6 millio n cones.
 * Cones ** function best in bright light. they are sensitive to light.

Conclusion
the job of the eye is very important, without it well you wouldn't see anything. it would be harder to walk and get around. so that's why we have them.