Understanding the Spectrum of Color Blindness

3. Protanomaly and Protanopia

People with red-green color blindness have a problem not only distinguishing between reds and greens, but also browns and oranges. Some even confuse blue and purple. There are two types of red-green blindness. Those who are sensitive to red light have protanomaly or protanopia. Protanomaly means the L-cones are defective while protanopia means they are missing and only short and medium-length cones are present. Those with protanomaly can see reddish brown instead of full red, as well as some purple and weaker greens. Those without L-cones do not see red or purple at all and green looks like yellow. Approximately one percent of men have this condition, compared to 0.02 to 0.03 percent of women.

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