FAQ: What is color blindness?
Color blindness is not a form of blindness at all, but a deficiency in the way you see color. When someone has a color deficiency, their perception of colors is different from most of us see. When the deficiency is more severe, it’s called color blindness.
People who are color blind are not aware of the differences between colors that seem extremely obvious to other people. Sometimes, someone may not even recognize they are color blind until they’re tested. This is because they don’t understand what they’re seeing isn’t how others see the colors of the rainbow.
While some people know what the basics of color blindness, we want to give you a better understanding of why color blindness happens, the different types and what people can do to see color again.
Who can become color blind?
A lot of people use the term “color blind”, but only a very small number of people are completely unable to see color, which is a condition called achromatopsia.
The terms color deficiency is more common in males than females. According to The Canadian Association of Optometrists, one in 10 males have a color deficiency.
Color deficiency is normally an inherited condition, which is passed from a mother to her child. But, it can sometimes be a result of certain diseases, trauma or a side effect from medication.
What causes color deficiency?
Color deficiency is a result of an imbalance in the three kinds of cones in the retina that allows us to perceive color. Inherited color blindness is on the X chromosome and men only have one X chromosome, while females have two X chromosomes. Inherited color blindness can be present at birth, begin in childhood, or not appear until the adult years.
Are there many types of color blindness?
The most common types of color blindness or color deficiency are inherited, like we mentioned earlier. These are a result of defects in the genes that have the instructions for making the photopigments found in cones.
Red-green color blindness is the most common type of hereditary color blindness. Hereditary color blindness is due to the loss or limited function of red cone or green cone photopigments. Genetic red-green color blindness affects males much more often than females, because the genes for the red and green color receptors are located on the X chromosome. Remember, men have one X chromosome while females have two.
Protanomaly: Those with protanomaly have abnormal red cone photopigment. Red, orange and yellow appear greener and colors are not as bright.
Protanopia: those with protanopia have no working red cone cells. Red becomes black and certain shades of orange, yellow and green can appear as yellow.
Deuteranomaly: Those with deuteranomaly have an abnormal green cone. Yellow and green tend to appear redder and it’s hard to see the difference between violet and blue. This is the most common form of color blindness.
Deuteranopia: Those with Deuteranopia have no working geen cone cells. Red becomes a brownish yellow color and green is beige.
Blue-Yellow Color Blindness is another form of color blindness. This type of color deficiency means that the blue-cone photopigments have limited or no function.
Tritanomaly: Those with tritanomaly have limited blue cone cells. Blue appears green and can be hard to tell the difference between yellow and red from pink. This is quite a rare type of color blindness.
Tritanopia: This type of blue-yellow color blindness means that there are a lack of blue cone cells. Blue becomes green and yellow is a light grey or violet color.
Complete color blindness is the final form of color blindness. This is exactly what the name refers to. People who are completely color blind do not see any color at all and the clearness of their vision may also be affected.
There are two types of complete color blindness
Rod monochromacy: This type of color blindness is rare and is the more severe form of the blindness. None of the cone cells have functional photopigments and it presents itself at birth. People with this type of color blindness see the world in black, white and grey.
Cone monochromacy: this type of color blindness happens when two of the three cone cells fail to work. There is red, green and blue cone monochromacy. When someone has cone monochromacy, they’re unable to distinguish colors because the brain needs to compare the signals from different types of cones in order to see the color. When only one cone works, this comparison is impossible.
How do we perceive color?
Have you ever wondered if the person next to you is seeing the same color as you? When you’re looking at a deep red sunset, is the person you’re beside looking at the same deep red color?
Color vision depends on our eyes and brain working together to see different properties of light. While we see natural and artificial light as white, it’s actually a mixture of colors. If it was perceived on their own, the color would span from deep blues to deep reds. You can see this happening when it rains and the rain separates sunlight into a rainbow.
The color of light is determined by its’ wavelength. Red light corresponds with a longer wavelength while blue light reflects a shorter wavelength.
Vision begins when light enters the eye and the cornea and lens focus it onto the retina. The retina is a thin layer of tissue that lines the very back of the inside of the eye, which contains millions of light-sensitive cells called photoreceptors. Some of these photoreceptors are shaped like rods and some are shaped like cones. The purpose of the retina is to convert the light into neural signals and send them on to the brain for visual recognition.
Rods and cones respond to light differently. Rods work better for dim light, which makes them extremely useful for night vision. Cones are more responsive to bright light, such as daylight.
Rods only contain one photopigment, which cones contain one of three different photopigments. Because of this, cones are sensitive to long (red), medium (green) or short (blue) wavelengths of light.
Most of us have all three of the different cone photopigments, so we share a similar color experience. But because color works with the eye and the brain, each of us can see color differently, even just slightly.
This means your red may be more red than someone else’s. Or, if someone else is color blind, your red and green could be their brown.
How do you diagnose color blindness?
There are a number of color blind tests that can be done to determine if you’re either color blind or have a color deficiency.
The most common color blind test is called the Ishihara, which tests for red-green color blindness. The test is a series of colored circles, which are called Ishihara plates. These contain a collection of dots in different colors.
Within the circle are dots that form a shape that is clearly visible to those with normal color vision. Those with a color deficiency or are color blind can not see anything. There is a newer form of this test called the Cambridge Color Test which uses the Ishihara but on a computer screen.
Can you treat color blindness?
Sadly for those who are color blind, there is no cure. That being said, those people with red-green color blindness are able to use special lenses to help them see colors more accurately.
There are also apps that help people with color blindness discriminate among colors.
Also, the is a special type of lens called the enchroma lens that can help a person distinguish shades with more distinction. It isn’t a cure, but for the right person, can improve color discrimination.
Ask us more
If you’re interested in learning more about color blindness, or would like to be tested for a color deficiency, contact us today.
We’d be happy to answer any of your questions.