Vision Anatomy


external image 4453-12596-14410-49917.jpg
I chose this picture because it give all the names and parts of the eye.
I chose this picture because it give all the names and parts of the eye.






The Eye!
The human eye ball is about 0.9 meters in diameter and is not completely round both the front and back is flattened a little bit. The eye has three parts to it the outer fibrous or sclera, the middle uveal or choroid layer, and the inner retina.

How the Human Eye Works!
http://www.afb.org/section.aspx?Documentid=201

An eye can be compared to a camera. In a camera, an image is created on film but on the eye, the image is created on the retina, a thin layer of light sensitive cells located in the back of the eye. The lens of the eye bends, or refracts, light that enters the eye.
The cornea a clear transparent covering in the front portion of the eye also contributes to focusing light on the retina. Nerve fibers extending back from the retina's nerve cells come together behind the retina to form the optic nerve, nerve fibers(also known as cables) connect the eye with the brain.
The optic nerve transmits messages about what we see from the eye to the brain. Like a camera, the human eye controls the amount of light that enters the eye through the lens under different light conditions.

20/20 Vision.
One chart that is commonly used for measuring 20/20 vision is the Snellen chart, which has letters of the alphabet arranged in lines , each line of letters from the bottom to the top. The letters on the lowest line are the smallest letters on the chart, and the letter at the top is the largest. The characters on the bottom line represent 20/20 vision; the large letters at the top represents 20/200, legal blindness.