color vision Flashcards
color vision
ability to discriminate between different wavelengths of light
S-cone
blue
L-cone
red
M-cone
green
visible spectrum
400nm (UV)-700nm (red)
color
perception of electromagnetic radiation of a specific wavelength
color can be specified by
its dominant wavelength and purity
can light be added together from two or more sources?
yes
2 basic types of color vision defects
- inherited
2. acquired
inherited color defect
- caused by an inherited genetic defect,
- present at birth (congenital), and remain constant throughout life
- absence of photoreceptor pigment
- both eyes
- red-green
- more males
- incurable
acquired color defect
- caused by accompanying
- diseases/trauma/toxicity. may be present at any time, and may change over time
- may differ between eyes
- usually changes over time
- blue yellow
- males and females equally
- sometimes treatable
Percentage of color deficient males
8%
percentage of color deficient females
0.5%
rods
does not preferentially detect light of certain wavelengths, but have a specific photopigment that detects light better in dim conditions
How many types of light sensing cells in the retina?
4
normal trichromats
normally functioning cones of all 3 types
anomalous trichromats
functional cones of all three types, but one type is sensitive to a different wavelength of light than in normal trichromats
dichromats
have only 2 types of functioning photopigments
monochromats
have only one single type of photopigment
-such that only rods or a single type of cone function normally
protanopia
dichromats that lack L-cone photopigment (red blind)
protanomalous
analmous trichromatic with functioning L-cone photopigment that is abnormal in sensitivity to red (red weak)
deuteranopia
lack of M cone photopigment (green)
deuteranomalous
functioning M-cone photopigment that is abnormal in sensitivity to green
tritanopia
lacking S cone photopigment
tritanomalous
functioning S-cone photopigment that is abnormal in sensitivity to blue
deutan
red-green
tritan
blue-yellow
monochromats
complete achromats
- have no ability to distinguish chromaticity
- entire visible spectrum seen as differing shades of gray
typical rod monochromats
- have only one functional rods (all three types of cones are dysfunctional)
- poor VA
- aversion to bright light
- central scotoma; often exhibit nystagmus as pre-teens
atypical cone monochromats
have only a single type of functional cone pigment; usually with normal VA
X-linked inheritance
L and M cone photopigment genes
Autosomal inheritance
rod and S cone photopigment genes
red-green defects
- most commonly encountered from inherited color defect
- X linked recessive, therefore much more common in males
Blue-yellow defects and Achromatopsia
very rare, but do exist
appropriate counseling
- parents
- type and severity
- haw it affects school, etc
- how relates to occupation
specific colored lenses
- do not restore normal color perception, but may aid color discrimination
- may help with aversion to light and poor VA of rod monochromats
acquired: causes by accompanying condition or toxicity
likely to be associated signs/symptoms that point to diagnosis
defect may differ between eyes and usually changes over time
a defect that is more severe in one eye or that appears to change over time is likely to be acquired
blue-yellow defect
acquired
affects males and females equally
acquired
chromatopsia
abnormal condition in which toxicity causes objects to be seen in a particular color or appear tinged with that color.
managing acquired CVD
- directed toward treatment of primary cause
- Dx primary cause involves other forms of testing and or consultation with other health care providers
- repeat color testing frequently
color vision testing
- lighting/viewing time/test distance
- wear corrective eyewear (no tint)
- usually one eye at a time
- done before using dx drugs, instruments with bright lights
- dont touch pages, store in dark
pseudochromatic (PIC) plate tests
- most common
- quick and easy
- used to efficiently screen for inherited red-green defects
arrangment tests
- useful for inherited and acquired defects
- specify type of defect and quantify severity
- sequence on hue, stauration
anomaloscopes
- most accurate for diagnosis, but usually only found in specialty clinics (costly)
- metameric matches
PIC plate tests-transformational plates
person with color defect reads one figure and those with normal color vision another
PIC plate tests-vanishing plates
person with color defect cannot read figure easily read by those with normal color vision
PIC test plats-hidden digit plates
person with normal color vision fails to read a figure those with a color defect are able to read
PIC test plates-diagnostic plates
figure is readable by those with one type of color vision defect, but not another
occupational tests of color vision
PIC tests
arrangment tests
color vision requirements
-drivers license - very few require color test.
-aircraft pilot- can be color blind, but depends on severity and what colors you can/can’t recognize
military- won’t be eligible for some MOS
