By Linda Conlin, ABOC/NCLEC
Every morning, before he left for work, my dad would ask my sister and me, “What color are my socks?” He was satisfied if we said they were brown. We thought he was either trying to get our brains primed for the school day, or he just hadn’t taken the time to check before he rushed out to catch the train. Like most kids in those days, we didn’t question our parents much.
Years later, I noticed that my son would only use crayons that had the paper wrappers on them. I chalked it up to the peculiarities of a five-year-old, along with not letting the different foods on the dinner plate touch. Not long after, my dad needed a physical for a job change which included a color vision test. He was found to have red/green color vision deficiency, or deuteranopia. The daily socks questions actually were for good reason!
I had my son’s color vision tested, and sure enough, he used crayons with the wrappers so he could read the names of the colors he couldn’t distinguish. His younger brother was found to have the same red/green deficiency. This isn’t surprising because deuteranopia is the result of a defect in a gene on the X chromosome. A woman can inherit it from her father, but have no symptoms herself because of her second, normal X chromosome. However, because the mother passes an X chromosome on to her son, there is a 50/50 chance he will inherit the color vision deficiency (CVD).
The genetic defect that causes a majority of CVD affects more than 13 million people in the United States. This defect results in diminished red/green, or the more rare blue/yellow color perception. But because most colors are a mixture of primary colors (red, green, blue), perception of the entire color palette is washed out, making the visual world a pretty dull place.
CVD patients learn to cope with their impairment as best they can. This can include a labeling system, organizing clothing by color and memorizing traffic signs and signals. CVD patients experience life differently from trichromats who have normal color vision, and from each other due to the variation in severity and type of deficiency. Some of these effects cause inconveniences, but others can be dangerous. One known issue related to CVD is reaction time. In general, reaction times are slower as the CVD patient is trying to find the shape or other stimulus they can associate with an object. Driving cars and dealing with signal lights, road signs, as well as daily tasks such as matching clothing (like socks), ripeness of fruits and complete cooking of foods can be stressful.
Although there are no cures for color blindness, gene therapies are being explored as a future solution. These treatments are currently not in human trials. Researchers inject human red photo pigment cells into the retinas of adult male squirrel monkeys. The monkeys, born without the necessary photoreceptors, are able to see trichromaticaly after the gene therapy. This proves that the brain has red "detection" in place, and the treatment has restored red/green sensitivity and normal trichromacy. For now, spectacle lenses and contact lenses specially designed to enhance color perception are available.
To find out more about color vision deficiency and color vision perception, check out the CE The Human Brain and Its Perception of Color at 2020mag.com/ce. And, Dad, I’m glad I understand why you were concerned about your socks.