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how does the spectral sensitivity graph of a protanope looks like?
- the s and m cones overlap from 400nm to 545nm.
- they have monochromacy above 545nm
- this is their distinguishable spectrum
- neutral point =492
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how does the spectral sensitivity graph of a deuteranope look like?
- similar to that of protanope overlap
- they won't be able to distinguish anything above 545 either (monochromacy)
- their neutral pt is 498nm though
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how does the spectral sensitivity graph of a tritanope look like?
- they don't have monochromacy!! (lucky them)
- neutral pt=569nm
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what is the genetics of tritanopes like?
- lack cyanolabe
- autosomal DOMINANT
- very few in both genders
- they can't distinguish blue from yellow but they can tell the difference in color using their red and green pigment
- confusion line = 569nm (aka neutral pt)
- yellow looks more pink and blue looks more green
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what is the wavelength discrimination like for tritanopes?
they have poorer wavelength discrimination
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what is tritanope's spectral sensitivity like?
- not as sensitive to lower wavelength of light cuz they don't have blue curve
- their luminous efficiency curve peaks at 555nm
- blue wavelength of light will look dimmer and they will need more intensity to detect them
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how are we physiologically organized at the fovea?
- tritanope!
- center of fovea only has L and M cones
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what is trichromacy?
- got 3 cones
- can match any spectral color with some combo of three suitable primaries
- types: normal and anomalous
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what are some types of anomalous trichomats?
- deuteranomlous trichromacy
- protanomalous
- tritanomalous
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what is anomalous trichromacy?
- protans and deutans are inTRAgenetic crossover defect
- result in abnormla gene (hybrid) for erythrolabe/chlorolabe
- they have shifted spectral sensitivity curve
- color matching, spectral sensitivity and wavelength discrimination characteristics as though they have less than normla amount of the affected pigment
- no confusion line - disorted macadams ellipse on CIE
- no co-punctal points
- no neutral points
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what is deuteranomaly?
- abnormal gene for chlorolabe - spectral sensitivity shifted slighted towards red
- x-link RECESSIVE
- 5% male
- 498nm least saturated
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what is protanomaly?
- abnormal gene for erytholabe
- Spectral sensitivity shifted slightly towards lower (greener) wavelengths.
- Or, erythrolabe is missing and there is a second M-cone (which is shifted towards longer wavelengths). They have two M cone genes, one of which is a hybrid that acts like an L cone photopigment
- x-link RECESSIVE
- 492 least saturated
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what is tritanomaly?
- abnormal gene for cyanolabe
- autosomal DOMINANT
- max photopic sensitivity at 555nm
- 570 nm appears least saturated
- normal trichromats will see yellow, tritans will see white
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what is the spectral saturation of anomalous trichromats like?
- able to distinguish color across the whole spectrum, but they need more saturation than normal trichromats
- can distinguish the wavelenghts dichromats can't (498, 498 and 569) but they need a lot of saturation to do it.
- the curve is shifted to the left and down
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anomlous trichromats wavelength discrimination
- x-axis = wavelength
- y-axis =just noticeable difference
- anamalous trichromats still have the double hump line on the graph as the normal trichromats so their discrimination is similar to a normal trichromat but is reduced
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what is color asthenopia?
- uncomfortable color vision
- Exhibited by some anomalous trichromats and even some normal trichromats
- Ability to discriminate among different wavelengths worsens with prolonged viewing until they behave as dichromat of the same "type" (i.e.,protan, deutan, or tritan).
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what is color amblyopia?
- Poor color discrimination that is not associated with any documentable pathology or genetic defect
- May be transient or permanent
- Very rare. You have to rule out everything else before you diagnose them with this
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what are some acquired color defects?
- We assume blue-yellow defect is acquired. They are very rare so it makes more sense clinically to assume that are acquired
- the disease progresses, so does the defect
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what is Kollner's Rule?
- Acquired blue-yellow defects are from ocular media,
- choroid, & distal (outer) layers of the retina.
- Acquired red-green defects are from the optic nerve and more proximal (inner) parts of the visual pathway
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how do you get acquired color defects?
- Trauma
- Disease
- Optic nervedamage
- Occupational exposure (chemicals)
- Toxicity to medications
- - Antibiotics
- -Antidepressants
- - Chloroquinines
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what is chromatopsia?
- A distortion of color vision such that the entire visual world appears tinted, as though viewed through a lightly colored filter
- xanothopsia and cyanopsia
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what is xanthopsia?
- Yellowish tint to visual world
- Temporary side-effect of fluorescein angiography
- Also associated with digitalis poisoning
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what is cyanopsia
- bluish tink to visual world
- frequently desribed by patients immediately after nuclear sclerotic cataract extraction
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what are some things you might see with acquired color vision anomalies?
- Nearly always associated with disease or injury
- May be monocular or more severe in one eye than the
- other
- May vary in severity over time
- May not exhibit typical deutan, protan, or tritan characteristics or test findings
- More likely to present with errors in color naming
- Equally prevalent among males and females
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Kollner's Rule of Thumb
- Blue-Yellow (tritan)
- - ocular media (nuclear sclerotic caratact)
- - outer r & choroid (ARMD)
- - diabetic retinopathy (this is inner retina so it's an exception)
- Red-Green (protan or deutan)
- - inner retina (toxic amblyopia; papillitis; Stargardt's)
- - optic nerve and neural pathways (optic neuritis MS)
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what are some exceptions to Kollner's Rule of thumb?
Glaucoma, papilledema, and dominantly inherited optic atrophy (all are optic nerve disorders) may be associated with B/Y (tritan) color vision deficits rather than the predicted R/G deficits
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hm... Kollner’s Rule is a “Rule of Thumb” (which rhymes with dumb)
- Many if not most (if not ALL) acquired red-green defects also exhibit blue-yellow defects
- Exceptions to Kollner’s Rule include glaucoma,
- papilledema, & all optic nerve disorders, which maybe associated with a blue/yellow defect
- Acquired defects may be UNILATERAL
- Congenital are always bilateral
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what is blackbody radiator?
a (theoretical) perfect radiator of electromagnetic energy, the spectral characteristics of which are defined entirely by the blackbody’s temperature
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what is color temperature?
- The color temperature of a light source is that temperature (in degrees Kelvin) of a blackbody radiator that produces the same spectral output as that of the real light source.
- “Color temperature” should be used to describe only incandescent light sources
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what is correlated color temperature?
The correlated color temperature is the temperature of a blackbody radiator that produces an output that most closely matches the color of the light emitted from a real non-incandescent source
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what are some CIE "standard illuminants"?
- illuminant A
- illuminant B
- illuminant C
- D (daylight) illuminants (D55, 65, 75)
- We need a standardized light source when doing color testing so we have consistent results. We want a light source that emits all wavelengths of light as equally as possible so it won’t affect the testing
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what is spectural locus on CIE?
the curved part of the CIE that has all the spectral wavelengths
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what is purple locus of CIE?
the straight part at the bottom
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what are non-spectral purples?
these colors are not made up by a single wavelength.You have to mix more than one wavelength to get these colors
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what is Planckian Locus of CIE?
- the line of various standard illuminants
- all of these are considered white light
- blackbody radiator "color temperature"
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explain illuminant A
- Definition: Blackbody radiator at 2856° K
- CIE Source: Gas-filled coiled-tungsten filament lamp with a fused-quartz envelope or window operating at 2854° K
- Function: Serves as standard for illuminants B & C
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explain illuminant B
- color temp: 4874° K
- CIE Source: Illuminant A + 1 cm thick double cell optical glass container (Davis-Gibson filter) filled with liquid chemical solutions B1 and B2
- Function: Mimics direct sunlight at noon (poorly)
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explain illuminant C
- Color Temperature: 6774° K
- CIE Source: Illuminant A + 1 cm thick double cell optical glass container (Davis-Gibson filter) filled with liquid chemical solutions C1 and C2
- Function: Mimics average direct Northern sunlight but lacks power in near UV range important for fluorescent materials
- Illuminant C is the illuminant for which nearly all clinical color vision tests were designed (approx best by MacBeth lamp)
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explain illuminant D
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explain illuminant D65
- Recommended for “Natural” Daylight
- Correlated Color Temperatures: 6500° K
- Fluorescent sources
- CIE Standard Source: NONE → functional tests are provided
- Acceptable substitute for Illuminant C in clinical color vision testin
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