The Eye

1. The Eye • The eye allows us to see and interpret the shapes, colorsand dimensions of objects in the world by processing the light they reflect or emit • The eye is able to see in bright or dim light, but it cannot see objects when light is absent

2. EYE The eye is an extension of the brain

3. Eye brain proximity • Can you see the Spinal cord?

4. Cross section You must know the position of: Pupil Retina Lens Iris Cornea Optic nerve Aqueous Humor Vitreous Humor

5. The Eye When you look at any object • Light waves from that object enter the eye first through the cornea,which is the clear dome at the front of the eye • Light waves progress through the pupil the circular opening in the center of the colored iris • Immediately behind the iris (and pupil) is the crystalline lens, and light passes through that also

6. The Eye • Light waves are bent (converged) first by the cornea, then even more so by the lens, to a point which is immediately behind the lens • At the nodal point, the light waves (image) become reversed (turned backwards) and inverted (turned upside down) • Light waves continue through the vitreous humor, the clear gel that makes up about 80% of the eye’s volume, and then back to a clear focus on the retina behind the vitreous

7. Retina – receives the image • Full of light receptors which are sensitive to: • Color and • Light levels • Massive blood supply is also needed

8. Retina receptors • Light receptors are called rods and cones • Rods are for fine movement • Cones are for color

9. Focusing on objects • The lens and cornea focus the light on the retina

10. Focusing • The lens’ job is to make the rays hit the same point …focus

11. Bending light • Light is bent to focus it as it passes through the lens • Lens thickness can be changed so the amount of bending is changed

12. Near vision-Presbyopia • to bend the light more to focus it • Fat lens needed

13. Far Sighted-Myopia • Rays enter the eye closer together • Need less bending • Thinner lens needed

14. Controlling light levels • Your eyes are very sensitive and can be damaged by harsh light. • Your iris controls light allowed into the eye by changing the size of the pupil

15. Diseases of the Eye • A cataract is a clouding of the eye's natural lens, which lies behind the iris and the pupil • The lens is mostly made of water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it. But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract, and over time, it may grow larger and cloud more of the lens, making it harder to see

16. Diseases of the Eye Glaucoma • Glaucoma represents injury to the optic nerve and pressure inside the eye. • Other patients may progressively lose vision and become blind

17. Diseases of the Eye • Researchers are identifying factors that may cause cataracts such as: • People with diabetes • Users of steroids, diuretics, and major tranquilizers • Users of a lot of salt • Cigarette smoke • Air pollution • Heavy alcohol consumption