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316 Colour Vision Flashcards

(69 cards)

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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
What’s chromatopsia
Vision appears to have a coloured tint like looking through tinted lenses BUT colour discrimination is normal
26
What’s Cyanopsia and it’s cause
Blue vision Cataract removal as it was supposed to absorb blue light Viagra
27
What’s xanthopsia and it’s cause
Yellow vision From medication e.g digoxin
28
What’s erythropsia and it’s cause
Red vision Snow blindness or atropine use
29
What’s chloropsia and it’s cause
Green vision Epinephrine or lead poisoning
30
What’s Ianthinopsia or violet vision
Violet vision Cannabis use
31
Why illumination important in Cv
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
What are the types of CV tests
Pseudoisochromatic plates - identify letter from background Hue discrimination/sorting tests - arrange hues in sequence Colour matching Colour naming
33
Example of hue discrimination/sorting test
D15 Desat D15 100hue
34
Example of colour matching
Anomaloscope MedmontC100
35
Example of colour naming
Falant Lantern CAD
36
Tests good for detecting THERE IS a CVD
Ishihara pseudoisochromatic plates Red desat test Farnsworth D15 Lanthonys Desat D15/Tritan album Etc
37
What’s good at DIAGNOSING the type of CVD
Medmont c100 Anomaloscope Lantern and CAD Rabin come contrast test
38
Why’s medmont c100 good for diagnosing CVD
Because it can differentiate programs and deutan CANT between dichromat and trichromats tho
39
How does anomaloscope diagnose CVD
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
How does lantern and CAD diagnose CVD type
Identify px with certain occupations
41
How does Rabin come contrast test diagnose by defect type
Sees if only one cone is affected or more than one cone affected
42
What does the anomaloscope determine
If normal or CVD if protan or deutan If dichromat or anomalous trichromat MOST reliable if matching wavelength widely separated
43
On an anomaloscope what do dichromat results look like
Dichromat - can match every red greed mix with a yellow luminance so line touches both ends matching 0 and 73
44
On an anomaloscope what do anomalous trichromat results look like
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
What do results if deutan and protan look like on anomaloscope
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
The munsell system defines colour by hue value and chroma what are these three
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
How does farnsworth munsell 100 hue work
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
How is error score calculated on F M 100 hue
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
What is 100 hue used for
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
What’s computer analysis if sorting tests for
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
What’s Rabin come contrast test
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
Describe lantern test
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
Why is lantern important for occupation
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
Describe Farnsworth Lantern “Falant”
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
Describe Holmes-Wright Lantern
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
Describe CAD Colour Assessment and Diagnosis
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
Why do we need History and VA in full colour vision assessment
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
``` In a full CV assessment what are things to watch out for in Ishihara D15 Medmont C100 Optec900 Anomaloscope CAD Farnsworth munsell 100 hue ```
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
General CV assessment order for occupations
Pass ishihara but if fail other test usually lantern needs to be passed Often exclude protan but accept mild deter animals
60
Reasons for CV standards
Safety as many lives stake and quick reaction time needed Accuracy to identify correctly Repeatability
61
Name CV tasks in aviation WITH AND WITHOUT redundancy
Without - PAPI precision Approach Path Indicator, parking lights WITH - navigation lights, rotating beacons on ground vehicles, Runway threshold
62
Police CV standard
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
Armed forces CV standard
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
Civil aviation authority CV standard | For class 1 2 or 3 medical certificate
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
Can a person with CVD fly
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
Marine CV standard
Must pass Holmes Wright Lantern B
67
Railways (Tram Driver) CV standard
Pass with ishihara but if failed then practical test used to assess suitability Tram drivers have no CV requirement
68
Firemen CV standard
No CV requirement
69
Electrical engineering CV standard
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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