Color blindness: Know the causes and symptoms

causes and symptoms of color blindnessShe: Honey, why is the color printer printing all funny?

He: Oh, one of the color inks must have run out. Let me replace it….


He: There you go! Now take another printout and check.

She: It’s perfect. Thank you, honey.

Just like that printer, your eye has its own print cartridges, and sometimes – in color blindness –the cartridges run out. But unlike the printer, the cartridges cannot be replaced.

What causes color blindness?

Color blindness is a genetic condition caused by a difference in how one or more of your light-sensitive cells in your eye responds to certain colors. The retina of the eye is made up of light-sensitive cells called rods and cones. The rods help you figure out the difference between light and dark. Whereas the cones help you figure out what color that light is.

There are three different types of cones: One responds to blue light, one responds to green light and one responds to red light. Your brain takes all the information from these different receptors and kind of mixes them into its own imaginary palette to give you the colorful impression of the world around you.

If there is something wrong with your red cones, the world looks devoid of red color. If your green cones malfunction, the green hues in the world sort of disappear. And in the same way if your blue cones don’t function to their full potential, you miss out the blues around us. We call all of these color deficiencies, commonly known as color blindness.

Color blindness in men and women

Color blindness is much more common in men. Almost one in every 10 men has it. But less than one in a 100 women has it. Why? It’s because of your genes. Most of our chromosomes come in pairs. We get one from each of our parents. But the X chromosomes are different. Women have two X chromosomes – one from their mom and one from their dad. Men only have one X chromosome they get from their mom and a Y chromosome they get from their dad.

Now the genes for color blindness are in the X chromosome. If a woman has something wrong with one of the X chromosomes, she has the other X chromosome to fall back on. To make a woman color blind, both the X chromosomes should be defective. But as a man has only one X chromosome, if that one chromosome is defective, there is no backup. This is why color blindness is more common in men.

Types of color blindness

Normally there are about six to seven million cones in your eyes. Depending on what happens to these cones, color blindness is divided into three broad categories:

  • Monochromatism:All the cones are malfunctioning or not available.
  • Dichromatism: Only two types of cones are available and functioning.
  • Anomalous Trichromatism: All three cones are available but with different sensitivity.

Dichromatism and trichomatism are further divided into three subsets depending on which color cone is missing or malfunctioning:

  • Tritanopia:Missing/malfunctioning blue cones.
  • Deuteranopia: Missing/malfunctioning green cones.
  • Protanopia: Missing/malfunctioning red cones.

But more than worrying about these scientific names, it is important to understand how to detect color blindness early in life.

Symptoms of color blindness

Nearly all people who are “color blind” can see colors but have difficulty distinguishing between certain colors. Not all people who are color blind have trouble with the same colors – most cannot distinguish between reds and greens in dim light; some cannot separate blues from yellows; and a very small group can see only black and white.

Usually, color blindness is detected in children when the parents are teaching the different colors. But in some cases the symptoms are so slight, they may not even be noticed. The main symptom of color blindness is a difficulty in distinguishing colors or in making mistakes when identifying colors. But there are other signs and symptoms that can point to color blindness. Some of them include the following:

  • Sensitivity to bright lights
  • Increased nasal perception (extraordinary sense of smell)
  • Headaches when looking at something on a red or green background
  • In some cases, improved night vision
  • Low attention span when it comes to coloring activities
  • Inability to see shades or tones of the same color
  • Rapid eye movement (in rare cases).

Color blindness test

normal-vision-coloursYou can easily detect color blindness at home itself. Draw twelve 2 cm x 2 cm squares on a white sheet of paper. The squares should be close to each other but shouldn’t touch.

Shade these squares with 12 different colors (make sure to include red, green, blue, orange, brown, grey and purple). Now take the paper to a place where there is good natural light (not strong sunlight) and ask the child to identify the colors.

If your child shows signs that they are not sure whether a color is red, green, brown, purple, blue or grey, there is a reasonable chance that they are red/green color blind. You should expect a red/green color blind child to be able to identify bright orange, yellow and pink (they can identify these colors by brightness and shade).

Once your suspicions have been aroused, get a formal diagnosis from an eye doctor. It is important that the specific type of color blind condition is diagnosed professionally because support provided in school needs to be tailored to suit each specific condition, and other issues related to color blindness may affect the ability to pursue certain careers.

10 interesting facts about color blindness

1 99 percent of all color blind people suffer from red-green color blindness.

2 The most annoying question to ask a color blind person is, “What color is this?”

3 In certain countries you need to have normal color vision to get a driver’s license.

4 While people with normal color vision can distinguish between more than 100 different hues, color blind people might only be able to distinguish up to 20 hues.

5 The anomaloscope is the most accurate color blindness test known today.

6 The most famous jobs which require normal color vision are police officer, firefighter and airline pilot.

Color-blindness-vision7 Unfortunately, in spite of the fantastic advances in medicine, there is no treatment or cure for color blindness.

8 You can improve color discrimination with the help of colored lenses or glasses, but you cannot get normal color vision.

9A father cannot pass on his red-green color blindness to his sons, but if a mother is red-green color blind, then all her sons will also be color blind.

10 John Dalton, who wrote the first known scientific paper regarding color blindness was color blind himself.


Color is one of the wonderful things in this beautiful world we live in. Though most people with color blindness do not seem outwardly handicapped, they are missing out. I feel for them.

Having said that, I know the world would be a better place if all of us would be color blind when it comes to distinguishing skin color.



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