Color Blindness: What Does it Really Mean?
Our retinas are made up of millions of tiny photoreceptor cells called rods and cones. Rods are responsible for perceiving light, and function mostly in low lighting and cones are responsible for our vision in bright light conditions and perceiving color. There are three types of cones: short wavelength cones “see” the color blue, medium wavelength cones see the color green, and long wavelength cones see the color red. To determine what color we are seeing, the visual processing system in our brain compares the intensity and wavelength of light that is absorbed by each type of our cones. The absorption of light rays by all of our cones produces the thousands of shades of colors people with normal color vision can perceive. When one or more of the types of cones is missing or defective, this is what causes a color vision deficiency. Often times, all 3 cones still exist, but one of the cones has decreased sensitivity to the light rays it is supposed to absorb.2
People with a color vision defect are not unable to see color altogether, but they have difficulty distinguishing between groups of colors and may only see a few shades of colors instead of thousands. Some colors may appear faded or washed out, while others may be identical to the way people with normal color vision see them.
The most common type of color blindness is a “red-green” deficiency, meaning people will have difficulty differentiating reds, oranges, browns and pinks from each other, and also greens, blues, and purples from each other3. But, another more rare type of color blindness known as “blue-yellow” also exists. In this type of color deficiency, people will have trouble deciphering between shades of blues from greens and different shades of yellows3. Even rarer, is the condition called achromatopsia which means a complete lack of cones. With no cones at all, this person will see the world in gray-scale (monochromatic) and will also have very poor vision.
While some color vision deficiencies can be a result of eye disease, most are usually inherited genetically .. aka, it is something you are born with. The way in which these genes are inherited (X-linked recessive) means that males are more predisposed to have a color vision problem than females. About 8% of males have some degree of color deficiency, and only 0.5% of females2. If the color vision defect is from genetics and not disease, it will not get worse over time.
Depending on the severity of a color deficiency, some people don’t even realize that they don’t see colors the way others do. Growing up as a child, everyone learns their colors the same way, and what you are told is a shade of “blue” is what you will identify with. It is not un-heard of that adults come in for an eye exam and find out that they have been color blind their whole life and never knew the difference. For the most part, having a mild color deficiency is something that doesn’t have a huge impact on one’s life.
It can however affect potential career options, for example: commercial pilots, police officers, and electricians (because of colored wiring). Professions like these require near perfect color vision to pass requirements. This is why it is important to know from an early age what kind of limitations your child may have when it comes to the impact on their future. It may also help explain why a child is having some difficulties with learning. It is important to inform your child’s teachers of all visual problems they have. Many teaching tools rely on color recognition, so it is important for them to know if your child is struggling in that area.
Routine eye examinations are recommended for all children. The Canadian Association of Optometry recommends regular eye exams for children, beginning at age 6 months, and then annual after the age of 3 until 18 years old.
- Kohl S, et al. A nonsense mutation in PDE6H causes autosomal-recessive incomplete achromatopsia. Am J Hum Genet. 2012.
- Color Vision Deficiency. AoA. 2013. http://www.aoa.org/patients-and-public/eye-and-vis...
- Color Deficiency. CAO. 2013. http://doctorsofoptometry.ca/colour-deficiency/