The Crazy Fabulous Human Eye
By: Becky Salisbury

The human eye is a really cool part of the body. It is part of the nervous system and is what we see out of. It’s pretty weird to think that we see out of this tiny hole in our eyes, and the eye is a lot more fascinating than some people may think or care. First off, the human eye has three layers. The Sclerotic coat, the Choroid coat, and the Retina make up these three layers. This diagram shows those layers.

So how does the eye work? Well, all the nerve impulses generated in the retina travel back to the brain by way of the axons in the optic nerve (also on diagram above.) The brain then does its thing, and that’s how we see! The lens (also above) is just behind the iris. This helps us to focus and adjust to see far away and close objects- just like a camera lens! The lens (eye’s lens that is) is held in place by zonules, extending from an encircling ring of muscle, called the ciliary muscle. Whether the muscle is relaxed or contracted decides whether the lens’ diameter increases or decreases, helping us adjust to see! Of course this system, like any system, is not perfect, and that’s where another type of lens comes in handy! (Glasses!). So what’s the deal about this? A too short eyeball, or too flat lens causes farsightedness, and too long eyeball or too spherical lens in contrast causes nearsightedness.









http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/V/Vision.html


http://www1.istockphoto.com/file_thumbview_approve/2347508/2/istockphoto_2347508_close_up_of_eye_and_glasses.jpg

http://www.cancerhelp.org.uk/cancer_images/eye.gif

http://hyperphysics.phy-astr.gsu.edu/Hbase/ligcon.html#c1