Color Vision Anomalies Flashcards
(145 cards)
1
Q
____% of the population manifests anomalous color vision
A
4.5
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
3
Q
Acquired color vision anomalies
A
- Less prevalent than hereditary anomalies
- secondary to disease or drug toxicity
- can be important diagnostic tool
4
Q
Missing one of the three cone photopigment
A
Dichromacy
5
Q
When does deuteranopia occur
A
When chlorolabe is missing
6
Q
Protanopia
A
Absence of erythrolabe
7
Q
Tritanopia
A
Absence of cyanolabe
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
9
Q
Three photopigment present, but the absorption spectrum of on of these photopigment is displaced to an abnormal position
A
Anomalous trichromacy
10
Q
Deuteranomalous trichromacy (deuteranomaly)
A
Chlorolabe spectrum is displaced toward longer wavelgnth
11
Q
Prtanomalous trichromacy (protanomly)
A
Erythrolabe spectrum is displaced towards shorter wavelgnth
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
13
Q
Deutranomly
A
M cone spectrum displaced toward longer wavelgnth
14
Q
Protanomly
A
The L cone spectrum is displaced toward shorter wavelgnth
15
Q
Erythrolabe affected
A
Protan
16
Q
Erythrolabe missing
A
Protanopia
17
Q
Erythrolabe absorption spectrum is displaced
A
Protanomalous (anomalous) trichromacy
18
Q
Chlorolabe is affected
A
Deutan
19
Q
Chlorolabe is missing
A
Deuteranopia
20
Q
Chlorolabe absorption spectrum is displaced
A
Deuteranomalous trichromacy
21
Q
Cyanolabe affected
A
Tritan
22
Q
People with ____ and ____ vision tend to confuse reds and greens
A
Protan and deutan
- RGcolor vision anomaly
- inherited usually
23
Q
Individuals with ____ vision confuse blue and yellow
A
Tritan
- BY color vision anomaly
- rarely inherited and almost always acquired
24
Q
Do people with color vision proces chromatic information differently than individuals with normal color vision?
A
Yes
25
Characteristics that distinguish anomalous color vision are
Spectral sensitivity, wavelgnth discrimination, color confusion lines, and the perception of saturation
26
What is the rarest color vision anomaly
Inherited tritan anomalies
27
The protanopia Vlambda curve is displaced how
Substantially displaced toward shorter wavelengths
28
The deuteranopia Vlambda curve is different how
Shoes a very slight displacement toward longer wavelengths
29
The displacement of the deuteranopia luminosity function is _____
Minimal
| -for clinical purposes it may be considered normal
30
Which color vision anomaly has a relatively normal luminance curve
Deuteranopia
31
What does the normal Vlambda function result from
The addition of M and L cone inputs
32
The absence of erythrolabe and the luminance curve
Protanopia, causes the luminance curve to be displaced toward shorter wavelengths
33
The absence of chlorolabe (deuteranopia) and the luminance curve
Causes the Vlambda function to be displaced toward longer wavelengths
34
The greater dislocation of the protanopia luminance function suggests what
That L cones play a greater role in generating the normal Vlambda function than do M cones
35
Why do people with protanopia find it difficult to see certain red objects
The Vlambda function is displaced toward shorter wavelgnth
36
Projecting a beam of light of 680nm light (red laser) onto a screen: normal vs protanopia
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
37
The luminosity functions in anomalous trichromacy vs dichromatic functions
Manifests the same general dislocation as dichromatic functions, but less pronounced
38
Protanomalous trichromacy and the luminosity function
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
39
Deuteranomalous trichromacy and the luminosity function
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
40
Which types of color vision anomalies have well-developed wavelengths discrimination in the region of 490nm
Protanopia and deuteranopia
-at longer wavelengths (>545) there is no ability to discriminate between stimuli on the basis of wavelgnth differences alone
41
What what wavelength is there no ability to discriminate between stimuli on the basis of wavelgnth differences alone in protanopia nad deuteranopia
Above 545
42
How many cone pigments do patients with deuteranopia and protanopia have that’s can absorb beyond 545nm
One
| -this manifests monochromatic color matching in this region of the spectrum
43
How are protanopia and deuteranopia patients able to discriminate stimuli longer than 545nm?
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
44
Origin of color confusion lines for each color vision anomaly is referred to as
Copunctal point
45
All colors falling along _______ are indistinguishable
Color confusion lines
46
Patients with deuteranopia and protanopia tend to confuse which two colors
Reds and greens, hence the term RG color anomaly
47
In tritanopia, which two colors are confused
Blues and yellow,s thus the term blue-yellow anomaly
48
In normal trichromacy, ___nm appears less saturated (more whiteish) than other wavelengths
570
49
Deuteranopia function for saturation shows the least amount of saturation at
498
| -appears white and are called neutral points
50
The protanopic function for saturation shows the least amount of saturation at
492
| -appears white and are referred to as neutral points
51
Neutral point in deuteranopia
498
52
Neutral point in protanopia
492
53
Neutral point in tritanopia
569
54
Neutral point in those with normal color vision and anomalous trichromacy
Do not manifest neutral points
55
How can you determine a neutral point based on color confusion lines in deuteranopia and protanopia
Where the confusion line passes through the white
| -all stimuli falling along one of these lines are confused with white
56
A person with dichromacy may report that a certain free traffic light appears
White
| -these traffic signals are approximate metamers of the dichromatic neutral points
57
Anomalous trichromacy and neutral points
They do not experience neutral points
| -the do display abnormal saturation perception
58
Deuteranomalous trichromacy and the least saturation
498
59
What wavelength shows the least amount of saturation in protanomalous trichromacy
492
60
Individuals with RG dichromacy are essential monochromatic for wavelengths beyond
Approximately 545
| -still label colors surprisingly well especially when other cues are available
61
What can people with RG dichromacy not label correctly
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
How does the spectrum appear to deuteranopia and protanopia patients /
Divided into blue and yellow regions separated by the neutral point wavelength, which is perceived as white
63
Where is wavelgnth discrimination best in deuteranopia and protanopia
In the region of the neutral point
64
How does the spectrum look for tritanopia
Red and green with a neutral point separating the two colors at 569
65
Between deuteranopia and protanopia, which one has a decrease in brightness in longer wavelengths
Protanopia
66
The majority of RG anomalies are ________
Inherited
| -X-linked recessive
67
RG anomalies are more common men or women
Men
68
Prevalence of RG anomalies is ____ dependent
Race
| -highest in whites
69
The most commonly inherited anomaly is
Anomalous trichromacy (protanomaly; dueteranomaly)
70
How are inherited tritan anomalies inherited
Autosomal dominant
| Extremely rare
71
A females must be _____ in order to express the color vision anomaly
Homozygous
| -the gene is recessive and she is usually just a carrier
72
Boys always receive the defective color vision gene from their
Mothers
73
If the father is affected with color deficiency and the mother us unaffected and not a carrier, how will that affect their offspring?
Sons will be unaffected
| All daughters will be carriers
74
If unaffected father and a carrier mother for color anomalies has offspring, how \will they affected?
50% of sons will be affected
| 50% of daughters will be carriers
75
The highly homologous genes for the M and L photopigment opsins are positioned on the _____ chromosome in a ______ array
X
| Head-to-tail array
76
Head-to-tail array of M and L cones on the X chromosome suggests what
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
The resultant hybrid gene from intragenetic crossover leads to
- normal photopigment, or
- the nonexpression of the photopigment (dichromacy), or
- an aberrant photopigment (anomalous trichromacy)
78
Molecular bassi of anomalous trichromacy
An aberrant photopigment from the hybrid genes resulting from intragenetic crossover of genetic material
79
A hybrid gene that differs substantially from the normal gene may result in
Severe anomalous trichromacy
| -the deviant photopigment absorption spectrum almost completely overlaps that of the other long wavelgnth photopigment
80
When the hybrid gene is more similar to the normal gene, the result may be
A milder form of anomalous trichromacy
| -the location of the deviant absorption spectrum is almost normal
81
Acquired anomalies of color vision
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
Inherited anomalies are secondary to
Stable physiological variations
| -remain unchanged throughout life and result in clear-cut results on color vision tests
83
The pathological processes that produce acquired anomalies are often
Variable in their course
| -result in color vision anomalies that may not be stable and may not produce clean test results
84
Inherited anomalies are unilateral or bilateral?
Bilateral and symmetric
85
Acquired anomalies are bilateral or unilateral?
May be unilateral or asymmetric
86
It must be assumed that any difference in the color vision of the two eyes is due to
An acquired anomaly
| -important to perform these monocularly when screening for conditions
87
Why is it important to test color vision monocularly
Because if someone has acquired anomaly in one eye and not the other, it could be missed and results could seem notrmal
88
Kollners rule
- 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
Aging changes in the lens leads to ______ color visions anomalies
Blue-yellow
90
Outer retinal diseases result in_________ color anomalies
Blue-yellow
91
Disease of the inner retina, optic nerve, visual pathways, and visual cortex results in _______ color anomalies
R-G
92
The nature of a______ defect can change over time
Acquired
| Can change from RG to BY
93
Can a patient manifest both a BY and RG anomaly simultaneously
Yes
- sometimes referred to as non selective loss
- optic neuritis
94
Rare conditions where the patient manifests monochromatic (or nearly monochromatic) vision
Achromatopsia
95
The most common achromatopsia
Autosomal recessive
| -can be complete and incomplete (residual M/L cone function)
96
Signs and symptoms of achromatopsia
No or very poor color discrimination, nystagmus, photophobia, and VA of 20/200
97
What kind of lenses minimize the bleaching of rhodopsin
Dark red
- permit rod function under brighter lighting conditions
- may be recommended
98
X linked achromatopsia
Very rare
Recessive manner
Magenta lenses
Contains S cones and rods
99
Cone monochromacy
Rare
VA normal, but monochromatic color matching
-defect in postreceptoral processing of color information
100
Retinal and cerebral achromatopsia
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
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
Chromatopsia
| -patients report that objects have a colored or tinged halo
102
When do chtromatopsias occur
Secondary to various medications
- digitalis (xanthopsia)
- fluorescein (xanthopsia)
103
Chromatopsia may follow
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
Most commonly used color vision tests
Pseudoisochromatic plate tests
- straightforward and easy
- number plates arranged in a book
105
Typical design of pseudoisochromatic plates
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
What do pseudoisochromatic plates not distinguish between
Dichromatic and anomalous trichromatic vision
107
What do pseudoisochromatic plates distinguish between
Protan and deutan anomalies
108
Do all color tests have plates to distinguish BY anomalies
No
109
Limitations of computer based vision tests that use pseudoisochromatic plates
The chromaticities of the plates may vary from computer to computer due to variations in hardware and software settings
110
Waggoner computerized color visio test
Monitor color calibrated is performed to overcome variations
111
Consists of 15 colored caps that form a hue circle within the CIE diagram
Farnsworth dichomatous test
112
The D-15 test is referred to as an
Arrangement test
113
How is the farnsworth D-15 test scored
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
What does the farnsworth D-15 tesl allow
The differentiation of protan, duetan, and tritan anamolies
115
What does the farnsworth D-15 not allow
The differentiation of dichromacy from anomalous trichromacy
116
Because the farnsworth D-15 has low sensitivity, what can happen
Certain individuals with anomalous trichromacy may pass the test
117
Advantage of the farnsworth D-15
Capacity to detect tritan losses (unlike ishihara)
118
What color test can detect tritans
Farnsworth D-15
119
HRR plates can differentiate
Protan
Deutan
Tritan
120
What can HRR not differentiate
If they shave anaomlous trichroamcy or if they are dichromat
121
Rabin cone contrast test (CCT)
- 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
Used for military
Rabin cone contrast
123
What is the only color vision test that can determine between a dichromat or a trichromat
Nagel anomaloscope
124
For nagel anaomaloscope, in protanopia, the luminance function is displaced
Toward shorter wavelgnth
125
The 546nm stimulus in nagel anomaloscope: protanopia
Appears bright
126
Nagel anomaloscope: protanopia, a the 670nm appears
Dim
127
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
Protanopia
128
_____ color anomalous remain stable throughout life and pose no threat to vision
Inherited
- can interfere with performance of cortina visual related activities
- let teachers know
129
Acquired color loss in child
Could indicate a central nervous system lesion and must be thoroughly investigated
130
Color vision standards and occupations
Some occupations have color visions requirements
131
People with RG color anomalies may have difficulty distinguishing among colors that are ________ or ________ if these colors fall along the red green confusion lines
Dark or desaturated
132
Do colored sunglasses interfere with the ability of patients with inherited anomalies to quickly and correctly identify color traffic signals?
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
Protan anomalies have been associated with an increased frequency of what kind of accedes
Rear end becasuse they cant tell the tail lights are red
134
Acquired anomalies are most commonly
BY
135
How should acquired color testing be
Monocularly
136
Lighting conditions for color vision testing
Standard illumination C lighting condition
| Macbeth lamp
137
Incandescent lightning and color vision testing
The patient may perform better than if the proper illumination were usd
138
Red contact lens used best in
Monchromat I
| -lets them act as a dichromat if worn in one eye
139
Are glasses a cure for someone with color deficiency
No
140
Gene therapy for color deficiency
The replacement of defective genes in people with color deficiencies offers the promise to cure color blindness
141
The ___ cone system is apparently more vulnerable to certain pathological processes than the other two cones
S cone
142
SWAP
Short wavelgnth automated perimetty
| -low number of S cones
143
Assess S system function in certain eye diseases
SWAP
144
Background for SAWP
Yellow to suppress M and L cones
145
Red desaturation test
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
