Red Green Color Blindness

Red green color blindness is by far the most common form of color blindness. An individual with this form of color blindness is not actually blind to both red and green at the same time, but rather either red color blind, or green color blind. The outcome is however the same, an inability to tell the difference between various hues of red and green.

Red Color Blindness – Protanopia & Protanomaly

Red color blind people can be categorised as follows:

  • Protanopia: the L-cones are missing, or non-functional, resulting in blindness to the red portion of the spectrum.
  • Protanomaly: The L-Cones are defective, operating below normal capacity to interfere with a person’s ability to see some shades of red.

People with defective L-cones (protanomaly) do not all suffer the same intensity of color blindness; some may have quite mild color blindness, whereas some may have a heavy disability. Interestingly a red color blind person will not only have trouble distinguishing between red and green hues, but also blue and green – one could argue that the term red green color blind is somewhat misleading!

Both forms of red color blindness are sex linked, due to the genes responsible for providing the correct coding to create L-Cones being found in the X chromosome. As discussed elsewhere on this website, females have two X chromosomes, where men only have one. A female who receives a defective X chromosome is likely only to be a carrier – and normally receives it from a color blind father. The second X chromosome is most likely going to be healthy, and will provide enough genetic information to ensure all 3 cone types are present in the eye.

Red color blindness is also considered a serious risk factor to drivers. Studies have found that red color blind individuals had a strong representation among the group of drivers who have crashed involving traffic lights and brake lights. Someone who has defective L-cones may still be able to differentiate the colors, but someone who has no L-cones will only see the red light as a ‘level of darkness’ and must be extra alert.

red color blindness green color blindness

Vischeck simulation of normal vision vs red green color blind vision

Green Color Blindness – Deuteranopia & Deuteranomaly

Green color blindness is by far the most common form; around 6% of the total male population is green color blind – primarily as a mild deficiency.

As with red color blindness, green color blind people can be categorised in two groups:

  • Deuteranopia: the M-cones are missing, or non-functional, resulting in blindness to the green portion of the spectrum. 5% of males and 0.1% of females suffer this form of green color blindness.
  • Deuteranomaly: The M-Cones are defective, operating below normal capacity to interfere with a person’s ability to see some shades of green, shifting color sensitivity toward the red sensitive L-cones. 1% of males and 0.35% of females suffer this form.

As with most forms of color blindness, Green color blindness is also sex linked, being passed on to children through faulty genetic coding in the X chromosome.