What causes color blindness?

Not everyone sees the world in the same hues. People with color blindness can, in many cases, see colors, but not in the same way as those with typical sight. So, what causes color blindness and people’s ability to see colors?

First, the term is actually a bit misleading. This condition is more aptly called a color vision deficiency, often affecting reds and greens, and occasionally blues as well. What causes color blindness depends on the type of color blindness in question, and how the light-detecting cells of the retina, known as rods and cones, function.

We rely on rods to see in the dark, while cone cells detect color. We rely on three different types of cones to see red, green, and blue. Color blindness occurs when a person's eye is missing one or more of these types of cones.

If just one type of cone is absent, a person may have a mild form of color blindness in which colors appear a little washed out in dim light but normal in good lighting. If all three are missing, a person may have severe color blindness and see everything in shades of gray. Missing all three cones is rarer, and this type is a less common form of color blindness.

Learn more below about color blindness, symptoms, and treatment options from the eye doctors at The EyeDoctors Optometrists. If you think you might be impacted by color blindness or other eye conditions, you can also learn more about our services and other eye diseases we help treat.

Who is affected by color blindness?

About 300 million people worldwide are color blind, about the same as the number of people who live in the U.S. The condition affects males more frequently, with about 1 in 12 men in the world being color blind. About 1 in 200 women are color blind.

Color blindness is most often passed down through genetics, but other conditions can also lead to being color blind. Keep reading for a breakdown of common causes.

Common causes of color blindness

In most cases, color blindness is a genetic condition passed down by parents through chromosomes. Red/green color blindness is more common in males. That's because it is passed down on the X chromosome, which males have only one copy of, while females have two.

If the one copy passed along by the mother is damaged, then a male will have red/green color blindness. However, females need to have color blindness passed down to them in both X chromosomes, the one from the mother and the one from the father, to inherit it.

Other varieties of the condition, such as blue/yellow color blindness, impact females and males equally. These are passed down in different sets of chromosomes.

Genetics are not the only cause of color blindness. Color blindness can be secondary to other diseases, such as:

• Development of cataracts

• Eye conditions such as glaucoma or macular degeneration

• The result of vascular disease

• Neurological conditions such as multiple sclerosis or Alzheimer's

• Injuries to the eye or brain

• Side effects from certain medications

Symptoms of color blindness

Except in very severe cases, color blindness may not be apparent in young children, particularly if the condition is mild. Some signs to look for include:

• Trouble telling the difference between similar colors

• Difficulty learning colors

• Difficulty noticing the brightness of colors

Those with very severe color blindness, known as achromatopsia, see the world in shades of gray. Such individuals also tend to have other symptoms, such as:

• Sensitivity to light

• Side-to-side eye movements (nystagmus)

• Lazy eye (amblyopia)

• Reduced vision

Possible treatments for color blindness

Currently, there is no definite cure for color blindness. Treatment often centers around managing issues that stem from color blindness. This may involve, for example, alerting a teacher ahead of time that a child is color blind so they can alter their lesson plans accordingly.

There are also several strategies for mitigating the everyday inconveniences of color blindness, such as placing colored clothing in a certain order. Some recent technology to help live with color blindness include:

• Special lenses that allow the person to distinguish between colors by filtering out some wavelengths of light. These can be used in spectacles or as contact lenses. A recent study found that a newly developed type of glasses for those with red/green color blindness can expand color vision even after the wearer takes them off.

• Smartphone apps can use a photo of an object to label the color by tapping on the object or a portion of it.

The condition doesn't have to be a significant limitation; often, with the aid of treatment, it may just be a question of seeing the world a little differently.