1. The Eye

2. Facts about the Eye Receptor organ for light About 2.5 cm in diameter
-Eye video (movie trailer)

3. ANATOMY

4. Ciliary
muscles
Zonular
ligaments
Macula

5. The 3 Layers of the Eye (from outside to inside)
All 3 are opaque (not transparent)
1) Sclera
White of the eye
Gives the eye its shape
Protects the eye
Becomes transparent in front of the eye (cornea)

6. 2) Choroid
Dark brown
Contains many blood vessels
Becomes the the colour part of our eye (iris) in front of the eye
-The iris is made up of 2 muscles and has an opening called the pupil
-The iris controls how much light enters the eye through the pupil by contracting its muscles
-The circular muscles close the opening of the pupil by contracting
-The radial muscles open the opening of the pupil by contracting

7. 3) The Retina -pinkish-beige membrane -the retina can sometimes detach due to violent shocks -composed of different types of the nerve cells, including the vision receptors -The two vision receptors (neurons) are rods and cones -there are 20 times more rods than cones

8. Cones:
-the cones are concentrated in a small circular area called the macula in the middle of the retina
-they can detect colour
-three types of cones: red, green, and blue
-certain colours stimulate one or more of the cones.
-white light stimulates all 3 cones
-cones provide the clearest image

9. Rods:
-the rods are located around the macula and throughout the retina
-detect contrasts not colours (ex. when you are in a dark room)
-more sensitive to light

10. -the optic disc contains no rods or cones, it is where the optic nerve begins.
-the optic disc is also called the blind spot

11. Ciliary
muscles
Zonular
ligaments
Macula

12. The Transparent Structures of the Eye
How light travels through these structures
Light -> cornea -> aqueous humour -> lens -> vitreous humor
Cornea:
-extension of the sclera
-its spherical shape helps transmit and converge light rays
2) Aqueous humour
-liquid, consisting mostly of water and a bit of glucose
-this liquid is continually replenished
-supplies glucose and oxygen to the lens and cornea

13. 3) Lens -lies behind iris -flexible -biconvex in shape -normally completely transparent, but with aging or illness can be come opaque (cataracts) -focuses the image onto the retina 4) Vitreous humor -lies between lens and retina -gelatinous liquid, mostly made of water -exerts pressure on the membranes which gives the eye its shape

14. Structures near the Eye and Their Functions
Eyebrows: stop sweat from running into eyes
Eyelashes: trap dust
Eyelids: spread tears over surface of eyes
Conjunctiva: covers the surface of the eye
Lacrimal glands: secrete tears
Tears protect the eyes by cleaning them with a bacterial agent
Excess tears run down your nose

15. PhysiologY

16. Lens Accomodation
When light passes through transparent structures it refracts or bends
Lenses also do this to light
The lens of our eye changes in shape to accommodate what we are looking at

17. The lens becomes more curved when trying to focus an object that is closer in order to converge the more divergent rays

18. Even though the image we see is inverted on our retina, our brain interprets it as being upright

19. Eye Problems and how to Correct them
Myopia or near-sighted
Cannot see far
-slightly elongated eyeball or overly curved lens
-clear image is in front of retina
-correction:
diverging lens (concave)

20. Hypermetropia (far-sighted) -difficulty seeing close objects -slightly shortened eyeball or under curved lens -clear image is located behind the retina Correction: converging (convex) lens

21. Presbyopia is similar to hypermetropia except that it is caused by loss of elasticity of the lens (usually related to agin)
Astigmatism is when your lens has an irregular curvature of cornea or lens
There is no clear image
You have difficulty seeing distant and nearby objects
Correction: cylindrical lenses

22. Nerve Impulse Pathway

23. Role
Pathway
Light
Receptor
Eye
Processor
Rods and Cones
Conductor
Optic nerve
Analyser
Visual Area of the brain