We can see colors because of color receptors in our eyes called cones. In normal human color vision, there are three different types of color receptors. The long wavelength cone, or L cone, is most sensitive to shades of red. The medium wavelength cone, or M cone, is most sensitive to shades of green. The short wavelength cone, or S cone, is most sensitive to blue. Whenever we look at a light, the brain will assess how each of the three types of cones responded in order to tell what color it is.
In most cases of colorblindness, one of the three types of cones is defective or missing, usually L cone, for red color, or the M cone for green. It is rare to have a defective S cone for seeing blue, or to have both the L and M cones be defective.
Because most colorblind people still have two types of functioning cones, they are able to see more than just black and white, it’s just fewer colors and a smaller variety of colors than what is seen with three types of functioning cones.
To demonstrate how colorblind people see different colors, look at these buttons. This is an unfiltered picture with many colors.
And this is what it looks like if you are missing the L cone. It would look similar if you were missing the M cone. People who are colorblind are still able to see several different colors of buttons, but some of the colors that look very different with normal color vision look very similar with colorblindness.
For example, the green buttons and the orange buttons look like different shades of the same color, and teal buttons and light purple buttons look nearly identical in color. Typically, children are tested for color blindness at an eye exam. Men are at much higher risk for being born with color blindness than women, who seldom have the problem.
Colorblindness doesn’t have a cure, and although it can make some activities more difficult, it doesn’t usually impact quality of life. In fact, there are some cases where colorblindness has even been advantageous. First, animals that are colorblind are less likely to be fooled by predators or prey that tries to use camouflage to blend into their surroundings. They rely on subtle changes in textures and outlines instead of color.
Second, in humans, the ability to not be fooled by camouflage has been observed and in World War II it was even considered an advantage to have a couple of colorblind soldiers present to help spot the enemy.
Also, because color vision is highly dependent on lighting, people who have normal color vision and rely heavily on color to see the world will also have a harder time seeing at night and low light situations than colorblind people.
BIO: Dr. Baldwin is an optometrist with Eye Surgeons Associates and practices at our Rock Island, IL clinic. His clinical interests include specialty contact lenses, ocular surface disease management, managing computer vision syndrome, pediatric eye care, and co-management of medical conditions that frequently affect vision. Dr. Baldwin speaks fluent Spanish.
The material contained in this article is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider.