Eye Crash Course

The Eye

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Eye anatomy

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Cornea: Transparent front surface of eye.

•  Protects the eye from dust and exterior objects.

• Acts as a lens bending rays of light.

 

Aqueous Humor: watery fluid fills space between cornea & iris.

•  Nourishes the cornea and lens.

• Gives the front of the eye its form and shape.

 Conjunctiva: Lines the inside of the eyelid.

• Covers the front of the white part of the eye or sclera.

• Its job is to produce mucus and lubricates the eye.

​https://www.youtube.com/watch?v=cEDIeQA3Oek

Open Ended

What is conjunctivitis (Pink Eye)?

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Sclera: white part of the eye.

•  Its job is to cover most of the eyeball.

 

 Iris: Ring of colored muscle around the pupil.

•  Changes the amount of light that enters the eye.

• Gives the eye its color.

 

Pupil: Hole through which light enters the eye.

•  Black in color.

• Covered by clear cornea.

• Controls the amount of light that enters the eye.

 

https://www.youtube.com/watch?v=55xE5Eh3kLU​

Poll

What color eyes do you have?

• Brown

• Blue

• Hazel

• Green

• Purple

Open Ended

Why do people have different eye colors?

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Dim light = pupil widens  = allows more light in.

         

Bright light = pupil narrows = allows less light in.

Multiple Select

Why do our pupils widen and contract?

• To let less light in

• to let more light in

• To let no light in

• They do not contract or widen

​Lens: Convex lens that directs incoming light.

• Located behind the pupil.

• Convex in shape.

• Refracts light and forms an image on the lining of the eyeball.

 

Ciliary Muscles: Controls accommodation of the lens.

• Contract to make the lens longer and thinner to see a distant object.

• Relax to make the lens shorter and fatter to see an object close-up.

Retina: layer of cells that lines the inside of the

eyeball.

• An upside down image formed on the retina.

• Made up of millions of rods and cones.

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Rods: Cells on the retina that detect dim light.

• Rods distinguish among black, white, & grays. 

• Allows you to see dim light. (night vision)

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Cones: Cells on the retina that detect color.

• Three types of cones: one detects red light, one detects green light, and one detects blue light. 

• Only functions in bright light; this is why it is hard to see colors in dim light.

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​https://www.youtube.com/watch?v=iUj7y7eqzkU

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Open Ended

How is the eye affected if someone is color blind?

Optic Nerve: Short, thick nerve that carries signals from eyes to the brain.

• The brain automatically turns the image right-side up.

• Your brain combines the two images, one from each eye, into a single three-dimensional (3-D) image.

 

Blind Spot: Part of retina where optic

nerve begins. – no rods or cones.

• You cannot see light that fall

  on the blind spot.

Vitreous Humor: Thick transparent fluid that fills the center of eye.

• Composed mainly of water.

• Comprises about 2/3 of the eye’s volume.

• Allows the eye to return to normal

  shape: flexibility.

 

Extraocular Muscles: Surround the eye &

controls its movement.

• There are a total of 6 tiny muscles.

•  Primary function is to move the eye

  left to right and up and down.

• Also moves eye inward & outward.

Normal vision

​https://www.youtube.com/watch?v=ypF037wlYZg

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When you focus on a DISTANT object, the ciliary muscles CONTRACT, making the lens LONGER and THINNER.

 

When you focus on a NEARBY (close-up) object, the ciliary muscles RELAX and the lens becomes SHORTER and FATTER.

 

Correcting vision

​https://www.youtube.com/watch?v=ypF037wlYZg

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The lens of your eye is a convex lens.  It is not a hard rigid lens, but rather a soft, flexible one.  So it can easily change shape to allow you to see clear images of both near and distant.

 

In some people, the eyeball is too long or too short, so the image on the retina is slightly out of focus so they must wear contact lenses or eyeglasses.

 

Some lenses in eyeglasses are convex and some are concave.

 

The type of lens used depends on whether the eyeball is too long or too short.

 

• Condition that causes a person to see distant objects as blurry.  They can see NEARBY (close-up) objects clearly.

• The eyeball is a little too long.

• The lens focuses the image in front of the retina.

• A nearsighted person can wear eyeglasses with concave lenses to see more clearly.

Nearsightedness

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Farsightedness

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• Condition that causes a person to see nearby (close-up) objects as blurry. They can see FAR or distant objects clearly.

•  The eyeball is a little too short.

• The lens focuses the image behind the retina.

• A farsighted person can wear eyeglasses with convex lenses to see more clearly.