M9.2 (eyes)

Question 1

Parts of the eye

Answer 1

Cornea
Iris & pupil
Lens
Retina
Fovea

Question 2

Cornea?

Answer 2

Clear window at front of eye, allows light to enter
Shape allows it to act as a fixed focusing device by bending incoming light rays

Question 3

How much of the eyes total focusing responsibility is the cornea responsible for?

Answer 3

70 - 80%

Question 4

Iris?

Answer 4

Varies the size of the pupil to control how much light enters the eye

Question 5

The pupils size can change…

Answer 5

Rapidly

Question 6

What ratio can light be adjusted by?

Answer 6

5:1

Question 7

What part of the eye is the iris?

Answer 7

Coloured

Question 8

What part of the eye is the pupil?

Answer 8

Dark centre section

Question 9

What does the lens use to change its shape?

Answer 9

Ciliary muscles

Question 10

What does the lens do?
And what is this called?

Answer 10

Adjusters the level of focus

Called accommodation

Question 11

When is the lens thickened?

Answer 11

Focus on close object

Question 12

Accommodation is compromised by what and what can it lead to?

Answer 12

Compromised by fatigue or aging

Lead to less sharp vision

Question 13

Where is the retina located?

Answer 13

Back of the eyeball

Question 14

The retina has what which are connected to what?

Answer 14

Nerve cells connected to the optic nerve

Question 15

What are the 2 types of nerve cells in the retina?

Answer 15

Cones and rods

Question 16

Cones?

Answer 16

Work in good light
Colour sensitive
Detect fine detail
Allows eye to see 1000 different colours

Question 17

Rods?

Answer 17

Don’t detect colours
Poor at distinguishing fine details
Good at detecting movement in peripheral vision

Question 18

When do rods take over from cones?

Answer 18

When the light decreases

Question 19

Rods and cones are stimulated by what?

Answer 19

Light

Question 20

Rods and cones transfer what?

Answer 20

Electrical impulses to the visual cortex in the brain via optic nerve

Question 21

Rods and cones transfer what?

Answer 21

Electrical impulses to the visual cortex in the brain via optic nerve

Question 22

What is there where the optic nerve joins the back of the eye?

Answer 22

A blind spot

Question 23

What is there where the optic nerve joins the back of the eye?

Answer 23

A blind spot

Question 24

Fovea?

Answer 24

A small depression in the centre of the retina
Responsible for central vision
Contains many cones
Where visual acuity at its highest

Question 25

Visual acuity?

Answer 25

The eyes ability to perceive sharp detail at varying distances

Question 26

How can visual acuity be assessed?

Answer 26

With a Snellen chart

20/20 vision (see 20 feet away clearly)

Question 27

Hypermetropia?

Answer 27

(Long sightedness)
When you have a shorter then normal eye ball, means the image is formed behind the retina

Question 28

Myopia?

Answer 28

(Short sightedness)
Eyeball longer then normal, image formed in front of retina

Question 29

Cataracts?

Answer 29

Clouding of lens
(Associated with age)

Question 30

Astigmatism?

Answer 30

A miss shaped cornea, distorts visual perception

Question 31

Migraine?

Answer 31

Severe headaches lead to visual disturbances

Question 32

Fatigue?

Answer 32

Temporary affect accommodation

Question 33

How does smoking affect vision?

Answer 33

Causes a build up of carbon monoxide in bloodstream which reduces oxygen supply to the eye.

Known as hypoxia which reduces sensitivity in rods

Question 34

How long does it take for rods and cones to adapt to a dark environment?

Answer 34

Cones - 7mins
Rods - 30 mins

Question 35

Contacts can be worn for how long?

Answer 35

8 - 12 hrs

Question 36

What can impart your vision when wearing glasses?

Answer 36

Dust
Rain
Mist

Question 37

Colour vision deficiency?

Answer 37

Colour blindness

Question 38

What causes colour blindness?

Answer 38

Defect in the structure of colour sensitive cones

Question 39

What % of men and women does colour blindness affect?

Answer 39

Men - 8%
Women - 0.5%

Question 40

What are the most common colour distinguishing for colour blindness

Answer 40

Red and green
Sometimes blue and yellow