Eyes

Question 1

Eye anotomy
(fluids)

Answer 1

There are 2 areas of fluid which give the eyes their shape.

• Vitreous humor (back)
• Aqueous humor (front)

Question 2

Eye anotomy (front)

Answer 2

Cornea - transparent layer protecting the eye on the ouside. Allows light to enter the eye and fall on th lense via iris
Iris - coloured area that changes size depending on the amount of light going throu it via the pupil. In low light, they enlarge. In bright less they are smaller.
Lens - located byhind the iris and changes change/stretches with assistance of ciliary muscles, to control focus. the greater the curvature, the greater the focus (occurs at a near object)

Question 3

Eye anotomy (back)

Answer 3

Retina: Light focused by the lense on a light-sensitive membrane

In the Retina, there are Rods and Cones photoreceptors connected to nerve cells

the most sensitive area of the Retina is Fovea because it has lots of ‘cones’ only

Rods and cones are not distributed evenly

Question 4

What are Rods

Answer 4

dark-seeing
help with peripheral vision
sensitive to movement
seeing in low light
not colour sensitive (only grey, blacks, whites)

located outside the foveal

Question 5

What are Cones

Answer 5

Light seeing - help with seeing in bright light / daylight:
- colour sensitive
- seeing in detail
- distant objectives

located in the central section of the retina (foveal)

Question 6

Visual interpretation

Answer 6

Retina converts the focused light into electrical impulses that reach the lower end of the brain and then routed to the visual vortex to interpret the info received from both eyes.

This info is then passed on to the cerebellum via the optic nerve, which helps us control movment and balance.

Question 7

What is Field of View

Answer 7

it’s the portion of the world we see with each eye (monocular vision) when stationary

usually 120 degrees Horizonal
150 degrees vertical

Question 8

What is the field of view when using binocular vision

Answer 8

there is an overlap of field of view at 60 degrees from the centre of the field

Question 9

What is the blind spot

Answer 9

In the binocular vision in each eye there is an area in the retina without rodes or cones(light sensitive cell) ‘5 degrees blind spot’ - it’s usually where the optic nerve leaves the eyeball.

the info/image missing in one eye’s blindspot is compensated by what the other eye sees - hence you need binocular vision.

“must move your focus of attention frequently to scan your surroundings’

Question 10

what is central vision

Answer 10

in the Fovea, there is an area of cone vision (1 degrees) that has the most visual acuity

Question 11

Peripheral vision

Answer 11

area that detects movement but can’t distinguish details (you will see it best you move your sight to the sides, as opposed to centre in dark light)

Question 12

what is binocular vision and its benefits

Answer 12

Binocular: using both eyes to focus

Benefits:
Eliminate risk of blindspots

Can see depth better: when looking at an object, each eye receives light from the object at different angles. The 2 images help the brain determine the distance of the object. The difference in both objects is greater when close vs far.

see in 3D

Question 13

What kind of vision (binocular or monocular) gives us depth and distance

Answer 13

binocular

Question 14

Types of depth and distance illusions

Answer 14

Parallax
head movements cause distant objects to appear to move relative to each other

Perspective
converging parallel

Relative size
Distant objects look small/closer objects look large

Relative motion
Distant objects appear to move slow/ closer objects appear to move fast

Overlapping motion
object in front of another appears closer

Aerial perspective
Distribution of light at a distance makes objects look blue

Question 15

How to protect the eyes from bright light

Answer 15

Eyes take a wide range of light conditions ranging from light to dark

High energy lights - blue and ultraviolets found at high altitude

Bright light is dangerous due to high UV wavelength. The effectds are cumulative and can lead to blindness

Use 100% UV protective sunglasses
high quality optical glass
impact resistant
thin frames
reduce glare and increase contrast in the dark

avoid photosensitive glasses as they don’t adapt to changing lights

avoid polarised glasses as they can conceal important colours in the instruments you use

Question 16

Affects of Dim light on the eye

DARK ADAPTATION

Answer 16

Dim lights reduce the resolution of objects, especially at a distance because cones don’t work in dark light and generally need brightt light to focus.

the pupils try to dilate to allow more light in (this takes seconds) but the Cones take 9 min and** rods take 30 min to fully adapt**

*anything affecting vision like hypoxia usually is more noticeable at night, even if below 10,000 ft)

Night vision can deteriorate at 4000 ft

*bright light inside affects vision at night

Question 17

how to manage with dim lights

Answer 17

• avoid bright white light (strobes, flashing, landing lights) 30 min before flying at night.
• avoid white light even inside the cockpit
• move your eyes 10 degrees to the side of an object, so that the light hits the rodes area more than the cones. Rodes help focus on objects in dim light

use red light in cockpit - it has less effects on the retina compared to green and bue

when switching from bright to dark - close one eye whilst the other is open

Question 18

Vision -
What is accommodation

Answer 18

ability of the eye to focus on close and distant objects

ie. far to close/close to far

deteriorates with age and tiredness

Question 19

what is myopia

Answer 19

Reflective Error due to shape of the eye or power of the lens

short sightedness
can focus up close but not far

need concave lense to fix

Question 20

hyperopia

Answer 20

long sightedness
can focus at a distance but not close
(ie reading)

need convex lens to correct

Question 21

Use of corrective lenses by pilots

Answer 21

Avoid using reading lenses because distant objects will be blurred

Use half moon lenses

Use bifocal lenses (not vifocal lenses)

Question 22

Visual system is comprised of 2 things:

Answer 22

optic nerve + visual vortex

Question 23

what’s the visual vortex

Answer 23

part in the brain responsible for processing info received by the eyes - processes motion, colour and shape

Question 24

function of the tear duct

Answer 24

washes the surfaces of the eye with antibiotic solution.

needs to be kept moist to help oxygen difuse thru

and protect from damage from dust particles

Question 25

visual acuity

Answer 25

capacity of the eye to resolve detail (depends on density of photoreceptors) depending on distance

12 megapixel resoultion vs 3megapixedl

with more distance, the less detail you can resolve

Question 26

where can alpha neumeric info be resolved

Answer 26

in the fovea because it’s the part of the retina that can process visual detail

Question 27

which part of the retina is better for resolving objects at night

Answer 27

rods that help with peripheral vision can detect movement of objectts in dim light or at night

Question 28

what are the 2 movements of the eye

Answer 28

Saccade and pursuit movements

Question 29

explain the movement of the eye

Answer 29

Saccades are directed towards stationary targets to align our visual axis to the object

pursuit is directed at moving targets

our eyes combine both movements with no conscious

eyes move by 6 muscles

Question 30

Normal acuity

Answer 30

ability to see 20/20 (6/6)

Question 31

in snellen chart, what does 20/40 mean?

Answer 31

a person is able to read the letters at a visual acuity of 20 feet compared to a normal person who can read it at 40 feet - this is a near sighted person

Question 32

factors affecting Visual Acuity

Answer 32

which angle of the eye you are seeing from

dark conditions

age

disease

dead photoreceptors

hypoxia

smoking, drinking, medication

short/near sightedness

external conditions (dust, weather, water, or anything that physically obscures object)

Question 33

why avoid photochromic sungalsses

Answer 33

don’t respond to changing light conditions, especially going from light to dark

they require UV light to function

Question 34

why avoid polarised glasses

Answer 34

adds polarising effects on screens and displays which hinders your visibility

Question 35

what is empty field myopia

Answer 35

if the eye has nothing to focus on, it resumes a default focus 1 - 2 metres.

if you are looking at distant threats, you will be unable to see them at first and must refocus

Look at distant objects in the environment, distant or at the horizon or even your wingtips - should do continuous scanning

Question 36

Detecting objects in the dark

Answer 36

1) the more the pupil enlarges, the less focus it has. It puts a lot of reliance on the lense to adjust focus

2)we have less rods near the fovea so hard to see objects i the dark in central view, so you may have to look at objects from the side a bit where there are more rods

Question 37

Tips for look out

Answer 37

• involve** a degree of frequent eye movement **to cover blind spots

BUT frequent eye movement might stop you from detecting ‘relevant movement’

• move attention to one erea, then keep still for a period (to help detected movement), then move to next area. Make sue that your vield of vision at each stop overlaps the previously searched area by 10 degrees
• **you can be on a collision course with another aircraft because there is no apparent relative motion between you and the other aircraft. Aircraft will get bigger and bigger.
  If you are flying 100 knots and aircraft is fying 500knots, then the rate of closure is 600knots (10nn per min)

the time you see the other aircraft depends on when you see the aircraft and the rate of closure.

If you see the aircraft at 1nm, you have 1/10th of a minute (6 seconds)
if you see the aircraft at 3nm, you you have 18 seconds

• **look at distant objects **in straight direction for focus
• **avoid empty field myopia **by consciously look at distant objects like a cloud, a wing tip otherwise your eyes will only focus at 1-2 m ahead and miss a distant aircraft

*be aware that in hazy conditons aircrafts whose edges are blurry/unclear may appear further than they really are.

LOOK OUT AT NIGHT

• need to rely on peripheral vision
• scan the sky more slowly than daylight
• look at objects from the side 10-20 degrees

Question 38

what is scotopic vision

Answer 38

distinguish light and dark - ie rods

Question 39

photobic vision

Answer 39

ability to detect colour - cones

Question 40

Color blindness (photopic)

Answer 40

Inability of detecting some colour due to imperfection in the cones or absense of hte cones - usually red and green

dangerous because you can’t see certain lights like nav lights or lights from ATC tower

Question 41

Ishihara cards

Answer 41

to test colour blindness

Question 42

Refractive errors

Answer 42

defect in shape of the eyeball or deffects in the power of the lens

here the plane of focus does not align with the retina, therefore need corrective lenses to bring the focus on the retina

Question 43

Astigmatism

Answer 43

imperfection in the shape of the cornea or lens. Causes uneven refractions of rays

so results in different optical power in different areas of the cornea or lens

difficult to resolve detail - image is distorted

can be corrected by lenses

Question 44

Symptoms of astigmatism

Answer 44

sometimes no symptoms

but with age it can become common

can cause headaches, blurred vision, lack of focus, squinting to focus

Question 45

Glaucoma

Answer 45

pressure on the retina impacting blood supply resulting in death of retina cells

happens suddenly and progress fast, by then treatment is too late — can cause lack of focus on details and blindness

can be medicated or surgery

caused with age

Question 46

cataracts

Answer 46

clouding of the lenses of the both eyes at same time

slow and progressive - can cause blindness

caused by age or chronic exposure to UV lights

in some cases you need to remove lenses and replace with artificial ones

Question 47

presbyopia

Answer 47

form of long sightedness but related to elasticity of the lense

causes difficulty in accommodation of near vison

can’t read small print in poor light or when tired

need lenses that don’t correct distant visioun but required for reading vision. Can use half moon convex in lower part of the lenses

Question 48

Sight is very sensitive when?

Answer 48

during hypoxia, or under drugs/alchohol or meds

G force

Question 49

How do eyes move?

Answer 49

Via the brain

3 Types of movements:
1) eyes are stationary but head moves
2) eyes move but head is stationary
3) both eyes move in harmony to track objects

Question 50

what is double vision

Answer 50

when eye muscle coordination fails/ hindered due to fatigue

Question 51

effects of glare

Answer 51

Pilot exposed to high intensity lights from all angles and is not protected from them.

also glare caused by bright environment and dark cockpit can make it hard to adjust quickly to read charts and instruments.

wear protective sunglasses as long as they don’t affect acuity

Question 52

effects of flickering lights

Answer 52

caused by sequence of light and shade (ie movement of propellor) usually affects hilicopter pilots

causes uneasiness

should wear sunglasses

should cover eyes or window

Question 53

Depth & distance perception

Answer 53

• Binocular vision helps
• clues from memory and experience that the eyes and brains use
• mathematical (ie size of object): bigger object appears closer
• Texture: the more visible the texture, the more close the object is.

Relative motion: closer objects appear to move fast compared to distant objects

Question 54

Texture

Answer 54

1) on final approach as you near the runway, its texture appear to flow outwards in all directions. It helps you maintain a constant approach slope to the aiming point

2) as you approach **flare height for landing, the texture of runways or grass passing by teh cockpit beccomes noticelable **

3)In hazy conditions, its difficult to see edges and details or texture so objectics appear closer ( you might down down closer)

Question 55

Visual illusions

Answer 55

images seen by the eyes are misinterpreted by the brain.

what we see in our brain isn’t the reality

Autokinesis
False expectation
Interpretting patterns
False horizone
Approaches: black hole, night approach, slope, size, obscuured

Question 56

Autokinesis

Answer 56

usualy happens at night

when you stare at a light object in the dark background at stationary position but you think it’s moving. This is because you lose focus at night and your eye is trying to focus.

This confuses pilot and might thing the object afar is moving when it’s not.

move your eyes in normal scanning, look at your instruments, focus on distant objects briefly

Question 57

false expectations

Answer 57

ex:

we expect a pencil to be smaller than a tree
but when both are seen next to each other in the same angular area of the retina, we assume the tree is further away.

A small image formed in the retina could be a distant rapid aircraft of a spec of dust

if you land at same runway, you are used to its width/length but if you land in a different runway, you are presented with different view even if the approach slope is correct

Question 58

Interpretation of pattersn

Answer 58

our brain makes sense of patterns of lines but interpretation may not always be correct

ex:
windshield has rain
you are appraoching and you perceive the runway to be in a specific location becdause your eyes see it this way but in fact, it is in a different location because of the light refacting on the water in the windshield.

Question 59

false horizon

Answer 59

cloud layers slope or angled lines seen at night may give a sense of horizon that is wrong

2 aircrafts at opposite ends of a sloping cloud look like they are on the same level

need check altitude and balance ball regularly

Question 60

Runways slopes

Answer 60

If the runway is on an up-slope, it will appear longer. You will feel you are high on slope and will tend to** make a shallower approach**

If the runway is on an down-slope, it will appear shorter. You will feel you are low on slope and will tend to make a higher approach

Question 61

runway size

Answer 61

**runway that is larger **than usual, will **appear close **than the reality

a runway that is smaller than usual will appear far than the reality

a wide runways, because of hte angle you view it in final stages of the approach, will cause illusion of being too low. **You will fly higher appraoch and overshoot/or land further after the runway threshold
**

a narrow runway, will causeillusion of being too high, and you might make contact with the runway earlier and harder. yOu will tend to fly a lower approach and land short

Question 62

haze

Answer 62

you might be closer to the runway than you may appear to be

Question 63

The night approach

Answer 63

Ideally use powered approach at night to ocntrol the lower rate of descent - here use PAPI

for correct tracking - try to ensure that the runway is symmetrical in the windshield

to guide you make the correct approach slope - look at the runway edge lights:

if only runway lights are used:
if you are too low, the lights intervals will be close
if you are too high, the ight intervals will be further

Question 64

black hole approach

Answer 64

when approaching a runway that ight have its edge lights but not other lights from the surrounding environment or terrain..common in runways surrounded by desert, waterbodies

you might think you are higher than the reality

might make steep descends/lower approach

use ILS or VASI or rely on altimeter and vertical speed indicator to control slope and rate of descent

Question 65

obscured approach

Answer 65

runnway obscured by snow for example, making depth and slope perception more difficult

Question 66

during the night, at 10000ft, your visual acuity has decreased.

what to do?

Answer 66

use supplementary oxygen

Question 67

Binocular cues

Answer 67

Depth perception:
using both eyes to get 2D images and form 3D images when you include the brain’s interpretation.

Retial disparity:
Depth perception at up to 60m.
Helps judge length of runway at up to 200 ft

using both eyes to get 2D images to form 3D images and the brain analyzes the difference to deduce distance.

Convergence
Produces depth info over 6-20 ft

when each eye moves inwards as an item gets closer and each eye sees an object from a different angle.

Question 67

Binocular cues
(for short distances)

Answer 67

Depth perception:
using both eyes to get 2D images and form 3D images when you include the brain’s interpretation.

Retial disparity/steropsis:
Depth perception at up to 60m.
Helps judge length of runway at up to 200 ft

using both eyes to get 2D images to form 3D images and the brain analyzes the difference to deduce distance.

Convergence
Produces depth info over 6-20 ft

when each eye moves inwards as an item gets closer and each eye sees an object from a different angle.

Question 68

Monocular vision
(for further distances)

Answer 68

Texture
Seeing extreme details mean items is close,
Seeing smooth surface mean items is far

Atmospheric/relative brightness:
items that are far are pale/blue

Motion Parallax:
when you are moving but stationary items at various distances appear to move at different speeds

Obstruction/overlap - objects covered by others look further away

Relative size/Retinal size: 2 items of same size, the closer one looks bigger

Linear perspective: more convergence, more distance

Height in visual field
if 2 items are on the same height relative to the angle of the observer, the item that occupies the retina spot the most is the ‘closer’ item

Question 69

spatial orientation

Answer 69

misinterpretation of aircraft speed, altitude or position because of conflicting info from senses (vision, equillibrium and seat of the pants’

Question 70

Even in case of spatial orientation…rely on your…

Answer 70

vision and instruments

Question 71

how long does it take to adapt to light and darkness

Answer 71

10 seconds to light

30 min to darkness

Question 72

pupil

Answer 72

regulates amount of light hitting the retina

Question 73

contact lenses can only be worn if

Answer 73

pilot is short sighted (as in he can see close, but cannot see far and requires long distance correction)

Question 74

contact lenses can cause issues in flight…

Answer 74

can dry up, cause itching, burning, etc

can increase corneal damage due to dehydration and mild hypoxia of the eye

they can dislodge and reduce visual acuity

usually good with peripheral vision than glasses

humidity doesn’t affection lenses

Question 75

if you fly into clouds in IMC, which sense should you rely on

Answer 75

Vision

Question 76

when scanning, how doesn the eye move and how is smooth vision achieved

Answer 76

the eye does jerky movements called ‘saccades’

smooth vision is achieved in the visual cortex of the brain

Question 77

if you see thunderstorms, you should

Answer 77

lightning might provoke a residual image in your retina, appearing in your vision for few minutes

to adapt to this high level of light, turn up the cockpit lights

Question 78

visual acuity at high altitude can be affected by

Answer 78

hypoxia and CO poisoning
smoking
anemea

Question 79

What is the order of light frequency we see (colour)

Answer 79

ROYGBIV
Lowest frequency to Highest
Red
Orange
Yellow
Green
Blue
Indego
Violent

combination of all = white light
Lack of all = Blackness

Question 80

what’s the % of info we process comes from

Answer 80

70% of info is visual from the eyes

Question 81

Acuity

Answer 81

Clarity / ability to see detail

The main focus of detail occurs within **10-15 degrees **

Seeing detail is affected by:

hypoxia
atmosheric clarity
distance from viewer
countor of object
relative movement
amount of light present
contrast

Question 82

field of view

Answer 82

120 degrees - left and right

150 degrees - up and down

overlap of 60 dgrees where bincolur view occurs

Question 83

colour blind

Answer 83

subtle
can be detected by specialized tests

Question 84

Night vision affected by

Answer 84

Hypoxia = 5000 ft

age, smoking, cabin pressure, drinking = 8000+ft

compensatory stage = 15,000 ft

Question 85

what should you do at night with cockpit light

Answer 85

**increase the lighting **to also prevent low vigilence

cockpit uses RED light as it affects Rods less than white light

Question 86

how do we see

Answer 86

—>50% of info enters the eyes
1) eye does jerky quick movements (saccade) and will (fixate) on an item =fraction of a second

2) eyes take 30-40 images per second which is what detects movement

3)2D images

–> 50% of info processed by braind
3) brain takes 1/50th of a second to process
–3D is learnt/created by. the brains
–expectectations and expereince is used
–brain fills the gaps
–illusions

Question 87

glare

Answer 87

too much light entering pupils

Question 88

red eye

Answer 88

when not all the light can be absorbed and some is reflected back

Question 89

old vs young people

Answer 89

old people need twice as much light than young people

Question 90

Visual Purples

Answer 90

these are rhodpsin in the Rods that help build up from light to dark in 30 min

need vitamin A

Question 91

Rods and Short vs Long wavelength

Answer 91

Rods can detect Blue objects instead of Red because blue has ‘short wave length’

rods are sensitive to shorter wavelength

Question 92

Photopic
Scotopic
Mescopic

Answer 92

Photopic - cones/central vision used in high intensity light

scotopic - rods/used for peripheral vision (see shades of grey) in low light

Mescopic: using rods and cones together but cones start to reduce colour perception. During dawn, dusk, full moon

Question 93

cornea bends light by %?
Lens bends light by %?

Answer 93

70%
30%

Question 94

function of the lens

Answer 94

helps with accommodation - focusing light into the retina

Question 95

what damage can the eye have

Answer 95

cornea is affected by** lack of humidity** (dries up) esp if wearing contacts

also the lens can be damaged by lack of humidity but also can get dislodged by g+ foce and rubbing

hypoxia

decompression - causes bubbles to form under the cornea

Question 96

ciliary muscles

Answer 96

help keep the lense focused

can get tired from too much focus

Question 97

pupils

Answer 97

control how much light enters

In low lights
big pupils = high depth of field = seeing less sharp or focused

in high light
small pupils = low depth of fiedl = seeing sharp/focused

Question 98

defective vision

Answer 98

Hypermytopia:
eyeball is short. image reflected behind retina. Longsightedness/farsightedness. can see far but not close
Convex lens required

myopia:
eyeball is long. image reflected infront retina. shortsightedness. can see close but not far. Concave lens required

Night myopia
myopia but see even better at night

Presobypia
A form of hypertopia where seeing close is difficult
hardening of lens. lower accommodation
comes with age

redlight presobypia
cannot see close/small intrustment print in red cockpit light

cataract - opague lens

glaucoma:
increase pressure of liquid in eyeball
interferes with accommodation
progressive narrowing of field of vision

astigmatisation: uneven curvurture of the lense . fixed with cylindriacal lense

Question 99

DERP

Answer 99

Design eye reference point

system/standard put in place to ensure you are sitting incockpit with best visibility of the outside and inside while making as head movements as possible

Question 100

sunglasses

Answer 100

Must:

abosorb most of visible light -85%

eliminate glare

do not decrease visual acuity

absorb UV and IR radiation

**ideally :
**neutral-grey
non polaraized
not photochromic (take 30 min bleaching time to adapt, can conceal instruments, may absorb more light then they should, rely on UV light which is blocked by windscreen)

Question 101

Wet winshield/prismatic effect

Answer 101

looking below at wet part, makes objects look Higher or Closer

Question 102

Rain

Answer 102

Makes you feel closer
forces low approach

Question 103

reflection on windshield

Answer 103

creates false horizon

Question 104

white out

Answer 104

when you see dark object with no shadow, background, horizon or anything

so you lose depth perception

Question 105

fog/haze

Answer 105

objects look far

Question 106

blackhole/Kraft

Answer 106

dark terrain with little lights
make you feel higher and further
so you make steep approach and land short

Question 107

upslope and downslope runway

Answer 107

Upslope:
feels like you are high
tend to undershoot/make low approach

Downslope
feel like you are low
tend to do high approach/overshoot

Question 108

Wide and narrow

Answer 108

Wide:
Feels low
high approach

Narrow
feels high
low approach

Question 109

bright light

Answer 109

makes you feel low
so you do high approach

Question 110

Mountain terrain

Answer 110

hard to fly level due to different sloping ground