1. Color Blindness

2. How the Eye Works
Rods, located in the peripheral retina, give us our night vision, but can not distinguish color.
Cones, located in the center of the retina (called the macula), are not much good at night but do let us perceive color during daylight conditions.
Each cone contains a light sensitive pigment which is sensitive over a range of wavelengths (each visible color is a different wavelength).

3. What is color Blindness?
Genes contain the coding instructions for pigments in the cones, if the coding instructions are wrong, then the wrong pigments will be produced, and the cones will be sensitive to different wavelengths of light (resulting in a color deficiency). The colors that we see are completely dependent on the sensitivity ranges of those pigments.
A mild color deficiency is present when one or more of the three cones light sensitive pigments are not quite right and their peak sensitivity is shifted
A more severe color deficiency is present when one or more of the cones light sensitive pigments is really wrong
8% of men and 0.5% of women have a color vision deficiency.
Inherited as a gene from the mother, presents on the X chromosome.

4. Acquired Color Vision Defects
Chronic illnesses which can lead to color blindness include Alzheimer’s disease, diabetes mellitus, glaucoma, leukaemia, liver disease, chronic alcoholism, macular degeneration, multiple sclerosis, Parkinson’s disease, sickle cell anaemia and retinitis pigmentosa.
Accidents or strokes that damage the retina or affect particular areas of the brain/eye can lead to color blindness.
Medications such as antibiotics, barbiturates, anti-tuberculosis drugs, high blood pressure medications and several medications to treat nervous disorders may cause color blindness.
Industrial or environmental chemicals such as carbon monoxide, carbon disulphide and some containing lead can also cause color blindness.
Age – in people over 60 years of age physical changes can occur which might affect a person’s capacity to see colors.

5. Color Deficiency

6. Types of Color Blindness or Vision Deficiencies
Trichromacy- Normal color vision uses all three types of light cones correctly.
People with normal color vision are known as trichromats.
Monochromasy - complete absence of any color sensation.
Protanomaly- a reduced sensitivity to red light
Deuteranomaly- a reduced sensitivity to green light and is the most common form of color blindness
Tritanomaly- a reduced sensitivity to blue light and is extremely rare.

7. Normal Vision Deuteranopia Deuteranopes are more likely to confuse:
reduced sensitivity to green light
Deuteranopes are more likely to confuse:
Mid-reds with mid-greens
Blue-greens with grey and mid-pinks
Bright greens with yellows
Pale pinks with light grey
Mid-reds with mid-brown
Light blues with lilac

8. Normal Vision Protanopia Protanopes are more likely to confuse:
reduced sensitivity to red light
Protanopes are more likely to confuse:
Black with many shades of red
Dark brown with dark green, dark orange and dark red
Some blues with some reds, purples and dark pinks
Mid-greens with some oranges

9. Normal Vision Tritanopia
reduced sensitivity to blue light
The most common color confusions for tritanopes are light blues with greys, dark purples with black, mid-greens with blues and oranges with reds.

10. Normal Vision Monochromacy No visible color only shades of grey

11. Testing for Color Blindness
Ishihara color blindness test
only test for red and green color deficiencies

14. Tetrachromacy Four cones. Ability to view more colors.
Can be function or non-functioning.
Hypothysis: 2-3% of female population. Tetrachromacy

15. 16 color cones: Mantis Shrimp

16. COMMON ANIMALS AND THE COLORS THEY CAN SEE
How other animals see…
COMMON ANIMALS AND THE COLORS THEY CAN SEE
ANIMAL
THE COLORS THEY SEE
RELATIVE TO HUMANS
SPIDERS (jumping spiders)
ULTRAVIOLET AND GREEN
Different
INSECTS (bees)
ULTRAVIOLET, BLUE, YELLOW
CRUSTACEANS (crayfish)
BLUE AND RED
Less
CEPHALOPODS (octopi and squids)
BLUE ONLY
FISH
MOST SEE JUST TWO COLORS
AMPHIBIANS (frogs)
MOST SEE SOME COLOR
REPTILES (snakes*)
SOME COLOR AND INFRARED
BIRDS
FIVE TO SEVEN COLORS
More
MAMMALS (cats)
TWO COLORS BUT WEAKLY
MAMMALS (dogs)
MAMMALS (rabbit)
BLUE AND GREEN
MAMMALS (rats)
ULTRAVIOLET, BLUE, GREEN
MAMMALS (squirrels)
BLUES AND YELLOWS
MAMMALS (primates-apes and chimps)
SAME AS HUMANS
Same
MAMMALS (African monkeys)
MAMMALS (South American monkeys)
CAN'T SEE RED WELL
* pit vipers, some boas and some pythons