Eye, Function

Question 1

What does the Cornea do?

Answer 1

It refracts (Bends) light as it enters the eye

Question 2

What does the Iris do?

Answer 2

It controls how much light enters the pupil

Question 3

What does the Lens do?

Answer 3

It focuses light onto the retina

Question 4

What does the Retina do?

Answer 4

It contains the light receptors

Question 5

What does the Optic Nerve do?

Answer 5

It carries impulses between the eye and the brain

Question 6

What do Rod Cells do?

Answer 6

They allow us to see in dimly lit areas

Question 7

What do Cone Cells do?

Answer 7

They allow us to pick up colour

Question 8

What is the way of remembering the function of Cone cells?

Answer 8

There are coloured cones in sport

Question 9

How many sets of muscles are there in the Iris?

Answer 9

2

Question 10

Which are they?

Answer 10

Circular Muscles & Radial Muscles

Question 11

What happens to the Radial Muscle when the Circular Muscle contracts?

Answer 11

It expands

Question 12

What happens to the Radial Muscle when the Circular Muscle relaxes?

Answer 12

It contracts

Question 13

What happens when a pupil dilates?

Answer 13

It expands to allow more light in

Question 14

What happens when a pupil constricts?

Answer 14

It shrinks to allow less light in

Question 15

What happens to the eye in bright light?

Answer 15

• Radial muscles of the iris relax.
• Circular muscles of the iris contract.
• Less light enters the eye through the contracted pupil.

Question 16

What happens to the eye in dim light?

Answer 16

• Radial muscles of the iris contract.
• Circular muscles of the iris relax.
• More light enters the eye through the dilated pupil.

Question 17

How do Pupil Reflexes work?

Answer 17

• The eye controls the amount of light falling onto the retina.
• When a receptor is stimulated, it sends a signal to the CNS, where the brain co-ordinates the response.
• But sometimes a very quick response is needed, one that does not need the involvement of the brain.
• Reflex actions are rapid and happen without us thinking.

Question 18

What is short sightedness?

Answer 18

Someone with short-sight can see near objects clearly, but can’t focus properly on distant objects. This is caused by the eyeball being elongated, so that the distance between the lens and the retina is too great. It can be corrected by placing a CONCAVE LENS in front of the eye.

Question 19

What is long sightedness?

Answer 19

Someone with long-sight can see distant objects clearly, but can’t focus properly on near objects. This is because the lens focuses the sharpest image behind the retina, instead of on it. This defect is often age-related, and due to a loss of elasticity in the lens. It is corrected by putting a CONVEX LENS in front of the eye.

Question 20

How do you remember which lens a short sighted person needs?

Answer 20

Concave sounds like conker, which is small.

Question 21

How do you remember which lens a long sighted person needs?

Answer 21

Someone Vexed is big and angry. Something big is usually long.

Question 22

Does a concave lens turn inwards or outwards? How do you remember?

Answer 22

The mouth of a CAVE curves INWARDS.

Question 23

Does a convex lens turn inwards or outwards? How do you remember?

Answer 23

A VEX, comes OUT to attack you.

Question 24

How do our eyes adjust to short distances?

Answer 24

For close objects, the ciliary muscles contract allowing the lens to go fat, thus bending more.

Question 25

How do our eyes adjust to long distances?

Answer 25

For distant objects, the ciliary muscles relax and the suspensory ligaments pull tight. This makes the lens pull thin - the light doesn’t.

Question 26

How does someone see?

Answer 26

Rays of light are refracted (bent) first by the cornea and then by the lens. They focus on the retina.

• The light rays then converge towards the retina.
• The lens is able to precisely focus the image because of its ability to change shape.
• Focusing on a distant object, the lens becomes thinner.
  Focusing on a near object, the lens becomes fatter.

Question 27

What are Cataracts?

Answer 27

• The lens develops cloudy patches, due to a build up of protein.
• Over time, the patches become bigger - causing blurry, misty vision and then eventually blindness.
• When young, our lenses are usually like clear glass, which lets us see through them.
• Cataract surgery involves removing the clouded lens and replacing it with a clear artificial lens.
  The artificial lens is placed in the same place as your natural lens.

Question 28

How does someone focus on objects?

Answer 28

Light is focused onto the retina by refraction at the cornea, and by the lens.
The lens changes shape to make the fine adjustments needed to produce a sharp image.
This is called accommodation.
As we get older, accommodation becomes slower and weaker.

Question 29

How do vision defects work?

Answer 29

• Short-sight and long-sight may be corrected by corneal surgery (‘laser surgery’), or by using appropriate lenses in spectacles or contact lenses.
• In recent years laser surgery has become more popular as a way to correct eyesight.
• The surgery usually involves reshaping the cornea – the transparent layer covering the front of the eye.

Question 30

How is colour blindness caused?

Answer 30

• Colour blindness is inherited meaning it is passed on from the parents to their child.
• The retina contains cells which are sensitive to either red, green or blue light.
• People who are colour blind have a lack of receptors, or have defects in them.
  -Some people can be colourblind with only a couple of colours; red-green colour blindness is when a person has difficulty distinguishing shades of red and green.