The Eye And Vision - Chapter 6

Question 1

Cornea is responsible for ______________% of the focussing of the eye

Answer 1

70% - 80%

Question 2

The lens does what?

Answer 2

The final focussing of the eye

Question 3

Iris controls the amount of…

Answer 3

Light entering the pupil.

This is controlled by the ANS.

Question 4

If the eye observes a close object, the pupil becomes:

Answer 4

Smaller

Question 5

If the eye observes an object at a distance, the pupil becomes:

Answer 5

Larger

Question 6

The lens uses which muscles to make a final focus, and what is the process called?

Answer 6

Ciliary muscles and this is a process of accommodation.

This can be affected by age and fatigue.

Question 7

If the lens focuses on an object close to it, the lens…

Answer 7

Thickens

Question 8

If the lens focuses on a distant object, the lens…

Answer 8

Flattens

Question 9

The image is __________ on the retina

Answer 9

Inverted

Question 10

Light sensitive cells near the retina are called:

Answer 10

Cones and rods

Question 11

Light sticking the rods and cones causes a _________________process which is then sent to the visual cortex via the optical nerve

Answer 11

Chemical, electrical process

Question 12

Centre of the retina is called:

Answer 12

The Fovea

Question 13

The fovea consists of:

Answer 13

Only cones

Question 14

Vision through the rods is

Answer 14

Scotopic vision

Question 15

Vision through the cones is

Answer 15

Photopic vision

Question 16

The C’s stand for?

Answer 16

Cones are Colour sensitive - Central Vision

Question 17

What do the rods see?

Answer 17

Black and white
Peripheral vision
Sensitive to low level light
Sensitive to movement

Question 18

As environmental light diminishes, so does….

Answer 18

Colour vision

Question 19

The Fovea is…

Answer 19

Central part of retina
Consists only of cones
Has the acuity of 20/20
Central vision is found here

Question 20

Alphanumeric Information is….

Answer 20

Reading

Question 21

Alphanumeric information reading is limited to

Answer 21

The Foveal area

Question 22

Visual field is defined as:

Answer 22

Central field + peripheral field = visual field

Question 23

20/20 is defined as:

Answer 23

You can see at 20ft what the normal person can see at 20 ft

Question 24

As your sight moves away from the Fovea, the effect is….

Answer 24

Rapid

Question 25

At 5' from the fovea you can see only ________ what you can at 20/20

Answer 25

Half

Question 26

At 25' away from the fovea you can see only _________ of 20/20

Answer 26

A tenth

Question 27

Acuity is affected by:

Answer 27

Angular distance from the fovea

Question 28

How long does it take the rods and cones to adapt to the light (from dark)

Answer 28

Cones - 10 seconds | Rods - 10 seconds

Question 29

How long does it take the rods and cones to adapt to the dark (from light)

Answer 29

Cones - 7 minutes | Rods - 30 minutes

Question 30

How is night vision affected by hypoxia, what stage is it in and at what altitude does it occur?

Answer 30

Hypoxia can cause a deterioration in night vision, it is in the indifferent stage and occurs at 5,000 ft

Question 31

Which works better for night vision, rods or cones?

Answer 31

Rods and they are more sensitive to low level light

Question 32

Night vision is affected by:

Answer 32

``` Cabin altitude Lack of vitamin A Age Mild Hypoxia Smoking ```

Question 33

Stereopsis

Answer 33

Depth Perception (up to 200ft)

Question 34

Blind spots

Answer 34

No light sensitive cells, found at the optic nerve

Question 35

Empty field myopia

Answer 35

If the eyes are rested, the natural focus distance is 1-1.5m

Question 36

Photochromic sunglasses are _________ for flying

Answer 36

Prohibited

Question 37

Polarised sunglasses are ____________ in flying

Answer 37

Discouraged

Question 38

Eye movement is controlled by how many muscles?

Answer 38

6 extrocular muscles

Question 39

Long sightedness

Answer 39

Hypermetropia

Question 40

Short sightedness

Answer 40

Myopia

Question 41

For both long and short sightedness, the eyeballs are:

Answer 41

Misshaped

Question 42

To fix long sightedness (hypermetropia)

Answer 42

Convex lens

Question 43

To fix short sightedness (Myopia)

Answer 43

Concave lens

Question 44

In short sightedness, the light...

Answer 44

Doesn't reach the back of the fovea

Question 45

In long sightedness, the light...

Answer 45

Makes an image behind the Fovea

Question 46

Presbyopia

Answer 46

Age affects eyesight This is because the ciliary muscles weaken and the lens grows less flexible and so affects accommodation. Causes a form of long sightedness.

Question 47

Astigmatism

Answer 47

Caused by a mis-shaped cornea

Question 48

Cataracts

Answer 48

Clouding of the lens This can be cured by surgery

Question 49

Correcting Specs

Answer 49

Another, spare pair is to be carried at all times whilst flying where they're easy to access.

Question 50

Glaucoma

Answer 50

Caused by a pressure rise of the liquid in the eye ball If left untreated, can lead to blindness Symptoms: - Acute pain in the eye - Blurred Vision - Sensitivity to high light levels - Visual field deterioration - Red discolouration of the eye

Question 51

Contact Lens's

Answer 51

Can cause damage to the cornea with low humidity May be dislodged by the rubbing of the eye, or an accidental knock Bifocal contact lenses are prohibited Must carry a pair of spare spectacles

Question 52

Colour blindness

Answer 52

Doesn't affect acuity Total colour blindness is rare Caused by defects in the cones Passed on through genes

Question 53

Monocular vision

Answer 53

A person with vision in only one eye cannot be accepted by EASA as fit to fly