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Perception Block 12 > Color Vision Anomalies > Flashcards

Color Vision Anomalies Flashcards

1
Q

____% of the population manifests anomalous color vision

A

4.5

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2
Q

Most prevalent color vision anomalies

A

Inherited

  • noprogressive and pose no threat to vision
  • may have profound effect on the performance of cortina activities, including those encountered at school and on the job
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3
Q

Acquired color vision anomalies

A
  • Less prevalent than hereditary anomalies
  • secondary to disease or drug toxicity
  • can be important diagnostic tool
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4
Q

Missing one of the three cone photopigment

A

Dichromacy

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5
Q

When does deuteranopia occur

A

When chlorolabe is missing

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6
Q

Protanopia

A

Absence of erythrolabe

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7
Q

Tritanopia

A

Absence of cyanolabe

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8
Q

The commonly accepted replacement model of deuteranopia and protanopia

A

The missing photopigment is replaced by a remaining photopigment

  • deuteranopia: chlorolabe replaced by eryhthrolabe
  • protanopia: erythrolabe replaced by chlorolabe
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9
Q

Three photopigment present, but the absorption spectrum of on of these photopigment is displaced to an abnormal position

A

Anomalous trichromacy

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10
Q

Deuteranomalous trichromacy (deuteranomaly)

A

Chlorolabe spectrum is displaced toward longer wavelgnth

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11
Q

Prtanomalous trichromacy (protanomly)

A

Erythrolabe spectrum is displaced towards shorter wavelgnth

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12
Q

Anamolous trichromacy: these diplacesmnt of the cone photopigment from their optimal positions results in

A

Deficiency color discrimination

-the greater the displacement of the photopigments, the more severe the color vision anomaly

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13
Q

Deutranomly

A

M cone spectrum displaced toward longer wavelgnth

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14
Q

Protanomly

A

The L cone spectrum is displaced toward shorter wavelgnth

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15
Q

Erythrolabe affected

A

Protan

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16
Q

Erythrolabe missing

A

Protanopia

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17
Q

Erythrolabe absorption spectrum is displaced

A

Protanomalous (anomalous) trichromacy

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18
Q

Chlorolabe is affected

A

Deutan

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19
Q

Chlorolabe is missing

A

Deuteranopia

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20
Q

Chlorolabe absorption spectrum is displaced

A

Deuteranomalous trichromacy

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21
Q

Cyanolabe affected

A

Tritan

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22
Q

People with ____ and ____ vision tend to confuse reds and greens

A

Protan and deutan

  • RGcolor vision anomaly
  • inherited usually
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23
Q

Individuals with ____ vision confuse blue and yellow

A

Tritan

  • BY color vision anomaly
  • rarely inherited and almost always acquired
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24
Q

Do people with color vision proces chromatic information differently than individuals with normal color vision?

A

Yes

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25
Q

Characteristics that distinguish anomalous color vision are

A

Spectral sensitivity, wavelgnth discrimination, color confusion lines, and the perception of saturation

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26
Q

What is the rarest color vision anomaly

A

Inherited tritan anomalies

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27
Q

The protanopia Vlambda curve is displaced how

A

Substantially displaced toward shorter wavelengths

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28
Q

The deuteranopia Vlambda curve is different how

A

Shoes a very slight displacement toward longer wavelengths

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29
Q

The displacement of the deuteranopia luminosity function is _____

A

Minimal

-for clinical purposes it may be considered normal

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30
Q

Which color vision anomaly has a relatively normal luminance curve

A

Deuteranopia

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31
Q

What does the normal Vlambda function result from

A

The addition of M and L cone inputs

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32
Q

The absence of erythrolabe and the luminance curve

A

Protanopia, causes the luminance curve to be displaced toward shorter wavelengths

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33
Q

The absence of chlorolabe (deuteranopia) and the luminance curve

A

Causes the Vlambda function to be displaced toward longer wavelengths

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34
Q

The greater dislocation of the protanopia luminance function suggests what

A

That L cones play a greater role in generating the normal Vlambda function than do M cones

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35
Q

Why do people with protanopia find it difficult to see certain red objects

A

The Vlambda function is displaced toward shorter wavelgnth

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36
Q

Projecting a beam of light of 680nm light (red laser) onto a screen: normal vs protanopia

A

This is easily seen as a bright red spot in normal color vision, but it is invisible to a person with protanopia
-since erythrolabe is absent, the 680,nm quanta of light are simply not absorbed

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37
Q

The luminosity functions in anomalous trichromacy vs dichromatic functions

A

Manifests the same general dislocation as dichromatic functions, but less pronounced

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38
Q

Protanomalous trichromacy and the luminosity function

A

The luminosity function is displaced toward shorter wavelgnth but less so then in protanopia
-as with protanopia, it may be difficult to see certain red objects

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39
Q

Deuteranomalous trichromacy and the luminosity function

A

Manifests minimal displacement of the luminosity toward longer wavelengths
-this displacement is even less than that found in deuteranopia, resulting in a function that is clinically normal

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40
Q

Which types of color vision anomalies have well-developed wavelengths discrimination in the region of 490nm

A

Protanopia and deuteranopia
-at longer wavelengths (>545) there is no ability to discriminate between stimuli on the basis of wavelgnth differences alone

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41
Q

What what wavelength is there no ability to discriminate between stimuli on the basis of wavelgnth differences alone in protanopia nad deuteranopia

A

Above 545

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42
Q

How many cone pigments do patients with deuteranopia and protanopia have that’s can absorb beyond 545nm

A

One

-this manifests monochromatic color matching in this region of the spectrum

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43
Q

How are protanopia and deuteranopia patients able to discriminate stimuli longer than 545nm?

A

Based on luminance

  • a stimulus at 575nm would appear brighter than an equal energy stimulus of 600nm
  • when equated for luminance, these stimuli are indistinguishable
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44
Q

Origin of color confusion lines for each color vision anomaly is referred to as

A

Copunctal point

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45
Q

All colors falling along _______ are indistinguishable

A

Color confusion lines

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46
Q

Patients with deuteranopia and protanopia tend to confuse which two colors

A

Reds and greens, hence the term RG color anomaly

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47
Q

In tritanopia, which two colors are confused

A

Blues and yellow,s thus the term blue-yellow anomaly

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48
Q

In normal trichromacy, ___nm appears less saturated (more whiteish) than other wavelengths

A

570

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49
Q

Deuteranopia function for saturation shows the least amount of saturation at

A

498

-appears white and are called neutral points

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50
Q

The protanopic function for saturation shows the least amount of saturation at

A

492

-appears white and are referred to as neutral points

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51
Q

Neutral point in deuteranopia

A

498

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52
Q

Neutral point in protanopia

A

492

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53
Q

Neutral point in tritanopia

A

569

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54
Q

Neutral point in those with normal color vision and anomalous trichromacy

A

Do not manifest neutral points

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55
Q

How can you determine a neutral point based on color confusion lines in deuteranopia and protanopia

A

Where the confusion line passes through the white

-all stimuli falling along one of these lines are confused with white

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56
Q

A person with dichromacy may report that a certain free traffic light appears

A

White

-these traffic signals are approximate metamers of the dichromatic neutral points

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57
Q

Anomalous trichromacy and neutral points

A

They do not experience neutral points

-the do display abnormal saturation perception

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58
Q

Deuteranomalous trichromacy and the least saturation

A

498

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59
Q

What wavelength shows the least amount of saturation in protanomalous trichromacy

A

492

60
Q

Individuals with RG dichromacy are essential monochromatic for wavelengths beyond

A

Approximately 545

-still label colors surprisingly well especially when other cues are available

61
Q

What can people with RG dichromacy not label correctly

A

They can label apples and bands properly because they know that other people call these objects certain colors

They cannot label patterns on a shirt that are plaid green and red
-may assign color labels on the basis of brightness cues and the context within the garment is worn

62
Q

How does the spectrum appear to deuteranopia and protanopia patients /

A

Divided into blue and yellow regions separated by the neutral point wavelength, which is perceived as white

63
Q

Where is wavelgnth discrimination best in deuteranopia and protanopia

A

In the region of the neutral point

64
Q

How does the spectrum look for tritanopia

A

Red and green with a neutral point separating the two colors at 569

65
Q

Between deuteranopia and protanopia, which one has a decrease in brightness in longer wavelengths

A

Protanopia

66
Q

The majority of RG anomalies are ________

A

Inherited

-X-linked recessive

67
Q

RG anomalies are more common men or women

A

Men

68
Q

Prevalence of RG anomalies is ____ dependent

A

Race

-highest in whites

69
Q

The most commonly inherited anomaly is

A

Anomalous trichromacy (protanomaly; dueteranomaly)

70
Q

How are inherited tritan anomalies inherited

A

Autosomal dominant

Extremely rare

71
Q

A females must be _____ in order to express the color vision anomaly

A

Homozygous

-the gene is recessive and she is usually just a carrier

72
Q

Boys always receive the defective color vision gene from their

A

Mothers

73
Q

If the father is affected with color deficiency and the mother us unaffected and not a carrier, how will that affect their offspring?

A

Sons will be unaffected

All daughters will be carriers

74
Q

If unaffected father and a carrier mother for color anomalies has offspring, how \will they affected?

A

50% of sons will be affected

50% of daughters will be carriers

75
Q

The highly homologous genes for the M and L photopigment opsins are positioned on the _____ chromosome in a ______ array

A

X

Head-to-tail array

76
Q

Head-to-tail array of M and L cones on the X chromosome suggests what

A

Erroneous crossover of genetic information could occur when the pair of X chromosomes aligns and exchanges genetic information during meiosis

The gene encoding for the M cone opsin could erroneously align with the gene encoding for the L cone opsin, leading to an unequal exchange of genetic information

  • one of the X chromosomes does not have the gene coding for the M cone opsin
  • offspring could have deuteranopia with this gene
  • other chromosomes has multiple copies and will not be affected
77
Q

The resultant hybrid gene from intragenetic crossover leads to

A
  • normal photopigment, or
  • the nonexpression of the photopigment (dichromacy), or
  • an aberrant photopigment (anomalous trichromacy)
78
Q

Molecular bassi of anomalous trichromacy

A

An aberrant photopigment from the hybrid genes resulting from intragenetic crossover of genetic material

79
Q

A hybrid gene that differs substantially from the normal gene may result in

A

Severe anomalous trichromacy

-the deviant photopigment absorption spectrum almost completely overlaps that of the other long wavelgnth photopigment

80
Q

When the hybrid gene is more similar to the normal gene, the result may be

A

A milder form of anomalous trichromacy

-the location of the deviant absorption spectrum is almost normal

81
Q

Acquired anomalies of color vision

A

Secondary to disease or toxicity and may be B-Y or R0G

-because B-Y are so rare, it must be assumed that such an anomaly is acquired until proven otherwise

82
Q

Inherited anomalies are secondary to

A

Stable physiological variations

-remain unchanged throughout life and result in clear-cut results on color vision tests

83
Q

The pathological processes that produce acquired anomalies are often

A

Variable in their course

-result in color vision anomalies that may not be stable and may not produce clean test results

84
Q

Inherited anomalies are unilateral or bilateral?

A

Bilateral and symmetric

85
Q

Acquired anomalies are bilateral or unilateral?

A

May be unilateral or asymmetric

86
Q

It must be assumed that any difference in the color vision of the two eyes is due to

A

An acquired anomaly

-important to perform these monocularly when screening for conditions

87
Q

Why is it important to test color vision monocularly

A

Because if someone has acquired anomaly in one eye and not the other, it could be missed and results could seem notrmal

88
Q

Kollners rule

A
  • Changes in the transmission properties of the crystalline lens secondary to aging result in blue-yellow color vision anomalies
  • outer retinal disease also result in blue-yellow color vision anomalies
  • disease of the inner retina, optic nerve, visual pathways, and visual cortex results in RG anomalies
89
Q

Aging changes in the lens leads to ______ color visions anomalies

A

Blue-yellow

90
Q

Outer retinal diseases result in_________ color anomalies

A

Blue-yellow

91
Q

Disease of the inner retina, optic nerve, visual pathways, and visual cortex results in _______ color anomalies

A

R-G

92
Q

The nature of a______ defect can change over time

A

Acquired

Can change from RG to BY

93
Q

Can a patient manifest both a BY and RG anomaly simultaneously

A

Yes

  • sometimes referred to as non selective loss
  • optic neuritis
94
Q

Rare conditions where the patient manifests monochromatic (or nearly monochromatic) vision

A

Achromatopsia

95
Q

The most common achromatopsia

A

Autosomal recessive

-can be complete and incomplete (residual M/L cone function)

96
Q

Signs and symptoms of achromatopsia

A

No or very poor color discrimination, nystagmus, photophobia, and VA of 20/200

97
Q

What kind of lenses minimize the bleaching of rhodopsin

A

Dark red

  • permit rod function under brighter lighting conditions
  • may be recommended
98
Q

X linked achromatopsia

A

Very rare
Recessive manner
Magenta lenses
Contains S cones and rods

99
Q

Cone monochromacy

A

Rare
VA normal, but monochromatic color matching
-defect in postreceptoral processing of color information

100
Q

Retinal and cerebral achromatopsia

A

Retinal is inherited and cerebral is due to a lesion in extrastriate cortex
-prior to developing the lesion, the patient has normal color perception, but subsequently perceives a black and white world

101
Q

These are not true color vision anomalies because they do not typically p[roduce a decreased ability to discriminate colors, they represent a distortion of color visions, like looking through a colored filter

A

Chromatopsia

-patients report that objects have a colored or tinged halo

102
Q

When do chtromatopsias occur

A

Secondary to various medications

  • digitalis (xanthopsia)
  • fluorescein (xanthopsia)
103
Q

Chromatopsia may follow

A

Cataract extraction

  • removal of nuclear sclerotic cataract exposed the retina to more blue light than it has experience in some time
  • results in cyanopsia
  • eventually diminishes
104
Q

Most commonly used color vision tests

A

Pseudoisochromatic plate tests

  • straightforward and easy
  • number plates arranged in a book
105
Q

Typical design of pseudoisochromatic plates

A

Vanishing plates

  • consist of a figure embedded in a spectral different background
  • the colors that constitute the figure and the background all fall on a common color confusion one
106
Q

What do pseudoisochromatic plates not distinguish between

A

Dichromatic and anomalous trichromatic vision

107
Q

What do pseudoisochromatic plates distinguish between

A

Protan and deutan anomalies

108
Q

Do all color tests have plates to distinguish BY anomalies

A

No

109
Q

Limitations of computer based vision tests that use pseudoisochromatic plates

A

The chromaticities of the plates may vary from computer to computer due to variations in hardware and software settings

110
Q

Waggoner computerized color visio test

A

Monitor color calibrated is performed to overcome variations

111
Q

Consists of 15 colored caps that form a hue circle within the CIE diagram

A

Farnsworth dichomatous test

112
Q

The D-15 test is referred to as an

A

Arrangement test

113
Q

How is the farnsworth D-15 test scored

A

By connecting the cap numbers in the sequence arranged by the patient
-anomalies may show crossovers on the hue circle that corresponds to color confusion lines

114
Q

What does the farnsworth D-15 tesl allow

A

The differentiation of protan, duetan, and tritan anamolies

115
Q

What does the farnsworth D-15 not allow

A

The differentiation of dichromacy from anomalous trichromacy

116
Q

Because the farnsworth D-15 has low sensitivity, what can happen

A

Certain individuals with anomalous trichromacy may pass the test

117
Q

Advantage of the farnsworth D-15

A

Capacity to detect tritan losses (unlike ishihara)

118
Q

What color test can detect tritans

A

Farnsworth D-15

119
Q

HRR plates can differentiate

A

Protan
Deutan
Tritan

120
Q

What can HRR not differentiate

A

If they shave anaomlous trichroamcy or if they are dichromat

121
Q

Rabin cone contrast test (CCT)

A
  • Allows assessment of the functionality of each of the three types of cones
  • uses computer
  • each column contains optotypes that are detectable based on contrast as defined for only one of the three cones
  • as the patient reads down a column, the cone contrast decreases until a threshold is reached
  • this test allows a cone threshold to be obtained for each of the three differnt cones
  • staircase procedure
122
Q

Used for military

A

Rabin cone contrast

123
Q

What is the only color vision test that can determine between a dichromat or a trichromat

A

Nagel anomaloscope

124
Q

For nagel anaomaloscope, in protanopia, the luminance function is displaced

A

Toward shorter wavelgnth

125
Q

The 546nm stimulus in nagel anomaloscope: protanopia

A

Appears bright

126
Q

Nagel anomaloscope: protanopia, a the 670nm appears

A

Dim

127
Q

A apatient with _______ adjusts the 590mn test field to a high radiance when matching 546nm and to a low radiance when matching 670nm

Nagel anomaloscope

A

Protanopia

128
Q

_____ color anomalous remain stable throughout life and pose no threat to vision

A

Inherited

  • can interfere with performance of cortina visual related activities
  • let teachers know
129
Q

Acquired color loss in child

A

Could indicate a central nervous system lesion and must be thoroughly investigated

130
Q

Color vision standards and occupations

A

Some occupations have color visions requirements

131
Q

People with RG color anomalies may have difficulty distinguishing among colors that are ________ or ________ if these colors fall along the red green confusion lines

A

Dark or desaturated

132
Q

Do colored sunglasses interfere with the ability of patients with inherited anomalies to quickly and correctly identify color traffic signals?

A

Certain non-neutral tints may make it more difficult for these individuals to detect and recognize traffic lights
-this suggests that color sunglasses should not be recommended for patients who have anomalous color vision

133
Q

Protan anomalies have been associated with an increased frequency of what kind of accedes

A

Rear end becasuse they cant tell the tail lights are red

134
Q

Acquired anomalies are most commonly

A

BY

135
Q

How should acquired color testing be

A

Monocularly

136
Q

Lighting conditions for color vision testing

A

Standard illumination C lighting condition

Macbeth lamp

137
Q

Incandescent lightning and color vision testing

A

The patient may perform better than if the proper illumination were usd

138
Q

Red contact lens used best in

A

Monchromat I

-lets them act as a dichromat if worn in one eye

139
Q

Are glasses a cure for someone with color deficiency

A

No

140
Q

Gene therapy for color deficiency

A

The replacement of defective genes in people with color deficiencies offers the promise to cure color blindness

141
Q

The ___ cone system is apparently more vulnerable to certain pathological processes than the other two cones

A

S cone

142
Q

SWAP

A

Short wavelgnth automated perimetty

-low number of S cones

143
Q

Assess S system function in certain eye diseases

A

SWAP

144
Q

Background for SAWP

A

Yellow to suppress M and L cones

145
Q

Red desaturation test

A

Comparison between two eyes looking at a red cap if you suspect one eye is has a deificneicy
-good for central and peripheral vision as well

Perception Block 12 (6 decks)

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