Color Vision Flashcards
what is the definition of color vision
the ability to discriminate a light stimulus as a function of its wavelength
what is the range of visible wavelengths that the eye can see
380-760 nm
what type of energy causes photoreactions on the retina to experience vision
electromagnetic
what is monochromatic light
colored light of a single wavelength
how do we see “white” light
it is created by mixing all colors created by a prism with a convex lens
what are the 3 additive primary colors
blue (435nm), green (545nm), and red (700nm)
what do the additive primary colors produce
white
what are the 3 subtractive primary colors
yellow, magenta-red, and cyan-blue
which light rays mix to create the subtractive primary colors
any two-thirds of the spectrum
what is subtractive color mixing
the mixing of color pigments or dyes
what do the subtractive primary colors produce
black
what are complementary colors
they have an additive mixture that forms white
what are interference colors
color that results from interference on thin films (soap bubbles)
why is the sky blue colored
the color was produced through the scatter of white light
which wavelengths, longer or shorter, become scattered as the rays pass through the atmosphere
the longer wavelengths
when do the sun’s ray’s give an intense red color
at sunrise and sunset, the sun’s ray’s pathlength is longer
which direction do the sun’s rays pass though the atmosphere
vertically
what is the shared chromophore in all visual pigments chemically related to
vitamin A
what makes the rods and cone cell pigments different
different opsin proteins
the genes encoding the opsin proteins are all members of what related receptor
G protein coupled receptors
what are G proteins in rod and cone cells called
transducins
are there different transducin forms for the different cone types
no they all share a common transducin form
do rods and cones have the same transducin form
no they each have a specific form
what reacts with an opsin protein to form a photoreceptor-pigment complex
11-cis isomer of aldehyde vitamin A
if the chromophore is in the opsin-bound state what happens
it has unique properties that contribute to color vision functioning
what is the opsin-shift
the change in absorption of the chromophore when it becomes bound to a particular opsin
what cells are needed for scotopic vision
rod cells (dim light)
what cells are needed for photopic and color vision
cone cells (bright-light)
which cells are less sensitive, rods or cones
cones are less sensitive but they can mediate differentiation of colors
what wavelength is the maximum for a rod response
510 nm
how many light rays apart can humans distinguish light rays
2 monochromatic light rays (2nm apart)
how many spectral colors does our color palette have
300 distinct spectral colors
what type of cells are in the fovea
high density of cones, NO rods, for color vision
what does the Young-Hemholtz theory emphasize
trichromacy
what confirmed the Young-Hemholtz theory
the discovery of 3 cone photoreceptor systems
what is the opponent theory (Karl Hering) based on
the hypothetical existence of three oppositional color pigment pairs
what are the 3 channels produced by the signals from the 3 cone types that are combined at the level of neurons
red-green, blue-yellow, and black-white
what is trichromatic vision
what our human vision is
what are the 3 physiologic detection systems
the 3 classes of photoreceptor cells (represent the 3 additive primary colors)
what are the 3 classes of photoreceptor cells
blue- short (s), green- middle (m), and red- long (L)
does the response of a cone cells change depending on the energy of the photon that captures it
no the response is always the same
what varies with photon energy
only the efficiency of a photon capture
what relates to the rate of photon captures
the dynamic output
what is the peak of the photopic curve
555nm
what is the peak of the scotopic curve
505nm
what does the scotopic curve represent
the photosensitivity of a single pigment rhodopsin
what percentage of males in the US are affected by a red-green color deficiency
up to 10%
what is the most common type of defect
deuteranomaly
what is tritanopia
loss of the S-sensitive wavelength gene
what is deuteranopia
loss of an M-sensitive wavelength gene, causes red-green defect
what is protanopia
loss of L-sensitive wavelength gene, causes red-green defect
what is a dichromat missing
missing one of three photopigments
what is a deuteranope missing
missing chlorolable (CD)
what is a protonope missing
erythrolabe (PE)
what is a tritanope missing
cyanolabe (CT)
what is a missing photopigment replaced with
other available pigments
what are anamolous trichromats
they have all 3 photopigments but only one pigment is displaced
if the color deficiency is congenital, will it be progressive
no
what is acquired color deficiency
not inherited, secondary to disease (blue-yellow)- textbook, not always the case
what is an achromatopia
the absence of multiple cone types and there is a severe loss in visual activity
what is the ishihara test
a collection of pseudoisochromatic plates used as a diagnostic tool (most widely used diagnostic tool)
what is an anomaloscope
an instrument used for precise follow-up testing
when would a person develop an acquired color vision defect
disease or exposure to drugs or toxins
what is an x-chrome CL
worn in one eye, reddish brown tint (patients may suppress that eye)
what type of color deficiency is most severely affected
dichromats
