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Colour Vision > 316 Colour Vision > Flashcards

316 Colour Vision Flashcards

1
Q

3 theories of colour vision

A

Young

Helmholtz

Hering

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2
Q

CV theory by young

A

Thought 3 primary colours in colour mixing = RGB

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3
Q

CV theory by helmholtz

A

Introduced overlapping spectral sensitivities that explains what happens at PR level of retina

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4
Q

CV theory by Hering

A

There’s 4 primary colours RGBY arranged in opponent pairs where third pair is luminance mechanism

Helps explain after images and proven as no reddish green colour

Current understanding of what happens from Ganglion cell level onwards

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5
Q

Characteristics of inherited colour vision defects

A

Present from birth where type and severity is same throughout life

Type can be diagnosed precisely

CVD affects BE equally but VA and VF normal

Mainly Red-Green and males

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6
Q

How are the confusion loci different from anomalous trichromats

A

Lines are shorter for an anomalous trichromatic and don’t include the full range of colours

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7
Q

What are monochromats

A

Can only see B&W cuz they only have rods or 1cone+rod (atypical)
SO VA is bad, they have photophobia and nystagmus

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8
Q

What are dichromats (Opias)

A

Have only 2 types of photo pigment (1 missing) so they have confusion Loci where colours that look the same

Note if luminance is controlled then they see a limited number of colours

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9
Q

What are trichromats

A

Have all 3 colour pigments and so can be colour normals or anomalous trichromats

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10
Q

What’s an anomalous trichromats

A

One photpigment has a different sensitivity

MOST COMMON CVD but can be mild or severe as dichromat

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11
Q

What’s an extreme anomalous trichromat

A

Px with possible abnormal medium AND long photopigments causing matching range of an anomalous cope extending to both sides of normal range instead of just one side in protanomal/deuteranomal

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12
Q

Prevalence of CVD

A

Anomalous trichromat

Deutan-> protan -> Tritan

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13
Q

Characteristics of acquired CVD

A

Onset after birth where type and severity changes with time

Hard to diagnose/classify

Monocular differences in severity CVD and decrease in VA/VF defects

Greater chance of B-Y defects and affects both Males and Females equally

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14
Q

What are the 2 common types of acquired CVD classification systems and what’s impt about it

A

Verriests Classification

Kollners rule

Impt as classifications can change v quickly if different optoms grade a CVD since acquired CVD changes as pathology worsens and different systems are used

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15
Q

Describe Verriests Classification (acquired CVD) Type 1

A

Protan like mild to severe confusion of RG hues

Little/no loss of BY

Moderate/severe reduction in VA

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16
Q

Describe Verriests Classification type 2

A

Deutan like, mild to severe confusion of RG hues

Mild loss of BY

Moderate to severe reduction in VA

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17
Q

Describe Verriests Classification type 3

A

Tritan like mild to moderate confusion of BY hues

Lesser impairment of RG

VA normal or moderately reduced

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18
Q

What does Kollners rule state and how is it innacurate

A

Blue-Yellow CVD are from disorders of retina while Red-Green CVD is from disorders of optic nerve

Many exception where many pathologies start with BY CVD and then become RG

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19
Q

Example of type 1 Verriest acquired CVD - protan like

A

Progressive cone dystrophies

RPE dystrophies

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20
Q

Example of type 2 Verriest classified acquired CVD (deutan like)

A

Optic neuritis

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21
Q

Example of type 3 acquired CVD Verriest - Tritan like

A

CSR/AMD

Rod and Rod-Cone dystrophies

Retinal vascular disorders

Peripheral retinal lesions

Glaucoma

AD optic atrophy

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22
Q

What’s acquired achromatopsia

A

Total colour blindness from injury to central occipital lobe

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23
Q

What’s Colour agnosia

A

Inability to recognise a colour while being able to perceive or distinguish it e.g thinking a blue banana is normal

Injury to V4

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24
Q

What’s colour anoma

A

Can point to colour of object but can’t say name

Injury to V4

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25
Q

What’s chromatopsia

A

Vision appears to have a coloured tint like looking through tinted lenses BUT colour discrimination is normal

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26
Q

What’s Cyanopsia and it’s cause

A

Blue vision

Cataract removal as it was supposed to absorb blue light

Viagra

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27
Q

What’s xanthopsia and it’s cause

A

Yellow vision

From medication e.g digoxin

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28
Q

What’s erythropsia and it’s cause

A

Red vision

Snow blindness or atropine use

29
Q

What’s chloropsia and it’s cause

A

Green vision

Epinephrine or lead poisoning

30
Q

What’s Ianthinopsia or violet vision

A

Violet vision

Cannabis use

31
Q

Why illumination important in Cv

A

Diff illumination changes appearance of colours so could be easier so px with CVD pass or harder so ppl with good discrimination make mistakes

32
Q

What are the types of CV tests

A

Pseudoisochromatic plates - identify letter from background

Hue discrimination/sorting tests - arrange hues in sequence

Colour matching

Colour naming

33
Q

Example of hue discrimination/sorting test

A

D15

Desat D15

100hue

34
Q

Example of colour matching

A

Anomaloscope

MedmontC100

35
Q

Example of colour naming

A

Falant Lantern

CAD

36
Q

Tests good for detecting THERE IS a CVD

A

Ishihara pseudoisochromatic plates

Red desat test

Farnsworth D15

Lanthonys Desat D15/Tritan album

Etc

37
Q

What’s good at DIAGNOSING the type of CVD

A

Medmont c100

Anomaloscope

Lantern and CAD

Rabin come contrast test

38
Q

Why’s medmont c100 good for diagnosing CVD

A

Because it can differentiate programs and deutan

CANT between dichromat and trichromats tho

39
Q

How does anomaloscope diagnose CVD

A

Looks at length of matching range and it’s orientation to give diagnosis of severity and type

Uses R+G = Yellow And looks at limit of matching so which colours look the same

40
Q

How does lantern and CAD diagnose CVD type

A

Identify px with certain occupations

41
Q

How does Rabin come contrast test diagnose by defect type

A

Sees if only one cone is affected or more than one cone affected

42
Q

What does the anomaloscope determine

A

If normal or CVD

if protan or deutan

If dichromat or anomalous trichromat

MOST reliable if matching wavelength widely separated

43
Q

On an anomaloscope what do dichromat results look like

A

Dichromat - can match every red greed mix with a yellow luminance so line touches both ends matching 0 and 73

44
Q

On an anomaloscope what do anomalous trichromat results look like

A

Have small matching range away from normal but if severe then have large matching range but not touching both ends

Protanomals ~ 40-73

Deuteranomals ~ 0-40

45
Q

What do results if deutan and protan look like on anomaloscope

A

Deutan - luminance level is contact so best fit line is horizontal

Protan luminance level is less when more reds is added so best for line is downward slope

46
Q

The munsell system defines colour by hue value and chroma what are these three

A

Hue is colour as commonly defined There’s 10 hues and Each hue has 10 steps

Value is amount of light reflected where 0 is black and 10 is white

Chroma is amount of colour present

47
Q

How does farnsworth munsell 100 hue work

A

Sorting test or hue discrimination

4 boxes of colour caps each box has 21 caps except first of 22 so has total of 85 and these caps vary only by hue so NOT value or chroma

Finds error score and compares to pop normals where performance is age related and there can be learning effects

48
Q

How is error score calculated on F M 100 hue

A

Compares each cap with one beside it and if in order there’s a difference of 1 each side giving total of 2

Subtract 2 from each result so if in order it’s a result of 0

Add score for each box and if <20 hrs superior CV, 20-100 average, >100 below average

49
Q

What is 100 hue used for

A

Not a screening test so no pass or fail BUT used to monitor or ass acquired CVD - beware learning effect

ALSO used to identify colour normals with very good colour discrimination like printing industry

50
Q

What’s computer analysis if sorting tests for

A

Reduced noise so helpful when error score is large when trying to find the axis of confusion

Uses vector analysis where S index is measure of randomness and C index is severity

51
Q

What’s Rabin come contrast test

A

Computer based test testing each cone function

Monocular test using similar letter to Bailey Logie but larger sizes for blue cone

Letter appear for 1-1.6 sec and if px doesnt select an answer within the time it’s markedlas incorrect

52
Q

Describe lantern test

A

Colour naming

Where one or 2 lights are shown and their colour has to be named

Usually can only use 3 or 4 names so have to decide if a yellowish light is closer to white or green or red

53
Q

Why is lantern important for occupation

A

Pilots have to be able to tel green from red lights to navigate and at night no other clues are available so have to be strict

54
Q

Describe Farnsworth Lantern “Falant”

A

2 vertically separated lights where px names lights using only red green and white

Normal room illumination with 8 feet test distance

One light of each pair is dimmer than the other so luminance cannot be used to distinguish colours

55
Q

Describe Holmes-Wright Lantern

A

Uses signal colour so 2 red 2 green + white

9 combinations used at test distance of 6m

Type A is aviation and 2 lights separated vertically

Type B is marine and 2 lights separated horizontally

56
Q

Describe CAD Colour Assessment and Diagnosis

A

CV test to establish colour discrimination limits that’s safe for pilots in civil aviation

Deuteranomalous px with CAD threshold <6SN and protanomlous px with <12SN have to do the PAPI test as well as normal trichromats

57
Q

Why do we need History and VA in full colour vision assessment

A

History - prev known/fam Hx, diff between eyes or time and wearing colour CL

VA - needs to be good for tests
most lanterns require clear distance vision
Other test are closer so needs reading glasses

58
Q 
In a full CV assessment what are things to watch out for in 
Ishihara 
D15
Medmont C100 
Optec900
Anomaloscope
CAD
Farnsworth munsell 100 hue
A

Ishihara monocular random order

D15 monocular and repeat if failed but I’d pass then go desat d15

Medmont C109 need average of 7 readings

Optec900 binocular distance glasses with lights

Anomaloscope if know inherited then either eye but if suspect acquired DO each eye separately

CAD and 100 hue blah blah

59
Q

General CV assessment order for occupations

A

Pass ishihara but if fail other test usually lantern needs to be passed

Often exclude protan but accept mild deter animals

60
Q

Reasons for CV standards

A

Safety as many lives stake and quick reaction time needed

Accuracy to identify correctly

Repeatability

61
Q

Name CV tasks in aviation WITH AND WITHOUT redundancy

A

Without - PAPI precision Approach Path Indicator, parking lights

WITH - navigation lights, rotating beacons on ground vehicles, Runway threshold

62
Q

Police CV standard

A

Ishihara 24 plate edition where if 3 or more errors made on plate 2-17 then need further check

With 100 hue, D15 or Falant confirmed with medmont c100

Criteria not met if any of further checks failed or protan defect found

63
Q

Armed forces CV standard

A

CPA is pass with ishihara or equivalent plates

CPB is fail with ishihara but pass with approved lantern

CPC is fail with both ishihara and lantern

64
Q

Civil aviation authority CV standard

For class 1 2 or 3 medical certificate

A

Ishihara 24 plate edition

If ishihara failed then (Holmes Wright lantern OR Falant) AND anomaloscope

If either lantern is passed and anomaloscope shoes CVD isn’t protan/anomalous then can get any of 3 certificates

If either lantern fails OR Falant pass with anomaloscope saying protan/anomalous then ONLY class 1 or 2 issued WITH restrictions

65
Q

Can a person with CVD fly

A

They need to be able to distinguish colours used in air navigation and correctly identify aviation coloured lights

So if they can’t do this then they can’t have a class 1 licence but can have class 2 with condition of flying only in daytime

66
Q

Marine CV standard

A

Must pass Holmes Wright Lantern B

67
Q

Railways (Tram Driver) CV standard

A

Pass with ishihara but if failed then practical test used to assess suitability

Tram drivers have no CV requirement

68
Q

Firemen CV standard

A

No CV requirement

69
Q

Electrical engineering CV standard

A

Pass on D15 means less mistakes when selecting electrical wiring

Live/active =brown or red
Neutral = light blue or black
Earth = green-yellow stripe or green

Colour Vision (2 decks)

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