7 Types of Color Blindness

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Color blindness 101

From guiding fashion trends to influencing our mood, color plays a big role in how we experience the world. Researchers estimate the human eye can detect upward of a million different color shades and tones in our daily lives.

At least, that’s true for most of us. According to the National Eye Institute, about 10 million Americans see the world through a different perspective due to some form of color blindness.

“Color vision deficiency is the inability to distinguish certain shades of color,” explains Robert Layman, OD, the president of the American Optometric Association. “While the term ‘color blindness‘ is also used to describe this visual condition, very few people are completely color blind.”

How do we see color?

The retina is a nerve layer in the back of our eye. This tissue contains special cells called cones that detect and react to different wavelengths—or colors—of light.

Each cone perceives either red, green, or blue light. Dr. Layman explains that a cone recognizes a color we see based on its respective wavelength: Reds have longer wavelengths while blues are short, and greens fall somewhere in the middle.

“Normally, the pigments inside these cones register different colors and send that information through the optic nerve to the brain,” he says. “This enables us to distinguish countless shades of color.”

But if one of these three types of cone is absent or simply not working properly, we won’t be able to see certain colors normally, explains Amanda Salter, MD, a comprehensive ophthalmologist at Shanbom Eye Specialist in Detroit.

The severity of this color vision loss depends on which cone—red, blue, or green—is defective or missing.

What causes color blindness?

Color blindness is an inherited condition caused by a mutation on the X chromosome. Dr. Layman says this recessive gene gets passed from a mother to her son—so color deficiency is much more common in people born male.

Global population research also shows this genetic trait most often affects people of European Caucasian descent, according to a study published in the Journal of the Optical Society of America.

“About 8 percent of white males are born with some degree of color deficiency,” Dr. Layman says.

Still, can women be color blind? While typically just genetic carriers, Dr. Layman says about 0.5 percent of females have a form of color vision loss.

This low rate among women is consistent around the world. However, a study published in Ophthalmology looked at how color blindness in men varies based on race and ethnicity, finding the condition affects approximately:

  • 3.1 percent of Asian males
  • 2.6 percent of Hispanic males
  • 1.4 percent of African males

Can you develop color blindness?

© mrs/Getty Images

Dr. Layman says that while most cases of color blindness are inherited, a disease or injury that damages parts of the eye—particularly the optic nerve or retina—can also cause loss of color recognition.

This acquired color blindness often affects just one eye and may progress over time, Dr. Salter adds.

A range of diseases can lead to this damage, including diabetes, glaucoma, macular degeneration, Alzheimer’s, Parkinson’s, multiple sclerosis, leukemia, sickle cell anemia, and chronic alcoholism.

Dr. Layman says other causes may include:

  • medications used to treat heart problems, high blood pressure, infections, nervous system disorders, and psychological problems
  • aging, as our ability to see colors can gradually reduce with age
  • contact with certain chemicals—such as fertilizers and styrene—that have been known to cause loss of color vision

Types of color blindness

“Most people with color vision deficiency can see colors,” Dr. Layman explains. Problems with certain cone cells just make it harder to differentiate between them.

He says people with these red, blue, or green cone deficiencies often see neutral or gray areas where the color in question should appear.

There are officially seven forms of color blindness, according to the National Eye Institute. These types fall into three categories: red-green color blindness, blue-yellow color blindness, and achromatopsia (or total color blindness.)

Red-green color blindness

The most common form of color blindness involves difficulty telling the difference between red and green.

People with this genetic trait have one of four conditions:

  • Deuteranomaly is a reduced sensitivity to green, making it look more like red.
  • Protanomaly is a reduced sensitivity to red, making it appear duller and greener.
  • Deuteranopia is the inability to see red wavelengths.
  • Protanopia is the inability to see green wavelengths.

Deuteranomaly and protanomaly are considered mild forms of color blindness that don’t generally get in the way of daily life. Because all three color cone cells are present—one is just not working normally—the conditions’ severity depends on the extent of the cone’s malfunctioning.

However, people with deuteranopia and protanopia are born with only two out of the three types of cone cells in their eyes. That’s why they cannot functionally tell the difference between green and red whatsoever.

Yet this total absence of a color cone cell is far less common—at least in humans. Research published in Royal Society Open Science found that dogs likely see the world similarly to people with deuteranopia.

Blue-yellow color blindness

Dr. Layman says blue-yellow color blindness is a rare but more severe form of color vision loss. That’s because people with this blue-yellow deficiency typically have red-green color blindness, too.

The condition affects the eye’s blue cone cells, which causes people to confuse blue with green and yellow with purple or pink.

There are two forms of this blue-yellow color blindness:

  • Tritanomaly occurs when the blue cone cells aren’t working properly, so blue looks green and yellow looks purple or gray.
  • Tritanopia occurs when the blue cone cell is missing, so people cannot discern blue from green, purple from red, yellow from pink, or blue from black.

Achromatopsia

People with achromatopsia are totally color-deficient, Dr. Layman says. This means they can only see things as black and white or in shades of gray.

Unlike other forms of color blindness, this condition is usually connected to a larger type of eye problem, says Jeffrey Dello Russo, MD, an ophthalmologic surgeon in New York City.

For example, people with achromatopsia can have additional vision issues like:

Some people with achromatopsia also have farsightedness or nearsightedness, according to the U.S. National Library of Medicine.

It’s the rarest form of color blindness, however, affecting about 1 in 30,000 people worldwide.

What’s it like to be color blind?

“Most color deficiencies are pretty subtle,” Dr. Dello Russo says. While there are varying degrees of color blindness severity, the condition doesn’t often interfere too much with people’s day-to-day lives.

You could even have poor color vision and not know it.

“Quite often, people with red-green deficiency aren’t aware of their problem because they’ve learned to see the ‘right’ color,” Dr. Layman explains. “For example, tree leaves are green, so they call the color they see green.”

That said, a study published in BMC Ophthalmology points to some ways in which color blindness can affect daily activities. The researchers’ surveys found that people with color blindness report some difficulty:

  • noticing skin color changes, like sunburns or moles
  • telling when food is cooked or fruit is ripe
  • buying clothes and choosing outfits
  • taking medication or checking the color of their urine
  • reading maps or color-coded charts

According to the National Eye Institute, children with color blindness might also need help with classroom activities and face limitations when it comes to future careers—like being a pilot or a graphic designer.

“Also, parents may not suspect their children have the condition until a situation causes confusion or misunderstanding,” Dr. Layman says.

“That is one reason the American Optometric Association (AOA) recommends that all children have comprehensive eye exams with a doctor of optometry before they begin school.”

How to get a color blind test

Color blindness tests are quite simple, Dr. Dello Russo says. Eye doctors use what are called pseudoisochromatic plates, a series of pictures made up of tiny colored dots.

“People go through these gradations and try to read the numbers embedded in these mosaic-looking images,” he says.

There are several types of these plates that help determine if a color vision deficiency exists and, if so, which type, Dr. Layman explains.

On some plates, people with normal color vision will see a number, while those with a deficiency do not. On others, people with color blindness will see a different number entirely.

“However, additional testing may be needed to determine the exact nature and degree of color deficiency,” he says.

Can color blindness be treated?

“There is no cure for inherited color deficiency,” Dr. Layman says.

Still, the severity of someone’s color blindness usually remains constant throughout their life and doesn’t lead to additional eye problems, vision loss, or blindness.

“But if the cause [of someone’s color blindness] is an illness or eye injury, treating these conditions may improve color vision,” he adds.

There may be treatment options on the horizon, however. Dr. Salter says researchers are currently exploring the potential of gene therapy to restore function to faulty color cone cells.

While this approach is still in its early stages, small human trials are underway, according to a 2020 report published in JAMA Ophthalmology.

In the meantime, experts recommend a few ways for people with color blindness to navigate daily activities:

Turn up the lights

Our eyes’ color cones don’t function well in the dark. Ensuring there’s good, bright lighting in the home or workspace can help people with color blindness tell the difference between colors.

Get tech support

There are several smartphone apps now available that can detect and name colors for you by using your phone’s camera. Most electronics today also offer accessibility options for people with color blindness, like color filters, contrast settings, and labeling options.

Consider color blind glasses

Special tinted lenses can help enhance the contrast between certain colors—particularly red and green—depending on the severity of someone’s color blindness, Dr. Salter says.

But make sure to talk to your eye doctor before using a pair. Dr. Layman says that for some people, certain tints can make it more difficult to see things like traffic signals, for example.

Now that you know about the types of color blindness, check out the signs you need reading glasses.

The coronavirus may live on certain surfaces for days

Covid-19 is still here. And a preliminary study published in the New England Journal of Medicine found that the virus can remain viable for up to 24 hours on cardboard and for two to three days on plastic and stainless steel; though another study in the Journal of Hospital Infection comparing it to SARS and MERS found it may be able to live on glass, metal, and plastic for up to nine days. Bottom line: it’s best to disinfect with the following cleaning products and these EPA-registered ones.

Bleach

Head to your laundry room and grab that bottle of bleach, according to Consumer Reports. Bleach is a great defense against viruses, and it has been a long time cleaning staple in and outside the laundry room. Don’t use it straight from the bottle though as that would be way too strong. Instead, mix a solution of ½ cup of bleach to a gallon of water. Use this to disinfect everything in your kitchen from the sink to the floor. You can even soak your child’s toys in a bleach mixture of 2 teaspoons bleach to 1 gallon of water, soak for two minutes, then rinse. Make sure you wear gloves when you use the beach, as it can be irritating and drying for your hands. Lastly, don’t keep the bleach solution for more than a few days, because bleach degrades some plastic containers.

Hydrogen peroxide

Head to the medicine cabinet, this time. Per the U.S. Centers for Disease Control and Prevention, common hydrogen peroxide (it should say 3 percent on it) will deactivate the rhinovirus, which is what causes the common cold. Technically, it “produces destructive hydroxyl free radicals that can attack membrane lipids, DNA, and essential cell components.” Since the rhinovirus is thought to be more difficult to ax than the coronavirus, it’s believed that hydrogen peroxide will work for this as well. Simply pop it into a spray bottle and spray it onto a surface. Let it sit for a few minutes before wiping away.

Isopropyl alcohol

Not to be confused with the alcohol you have in your bar closet, this is an alcohol solution with at least 70 percent alcohol. No need to dilute it, according to Consumer Reports. It’s safe for cleaning every surface but beware of plastics, as it may cause discoloration. Try this bottle, which has more than 99 percent pure isopropyl alcohol.

Soap and water

You’ve likely been hearing so much about this one already, hopefully, you still have some good ol’ fashioned soap remaining. Wash your hands thoroughly, with warm water and soap for 20 seconds. Soap works better than disinfectants if you’re attempting to destroy viruses, according to Marketwatch. It does this by dissolving the fat membrane so the virus becomes inactive. Yup, just your regular soap. Make sure you’re using a clean towel to dry them. Does washing clothes with soap and water protect against coronavirus? What you need to know.

Skip: Homemade hand sanitizer

Contrary to popular social media opinion, homemade hand sanitizer may not work as well as your friends may have you believe. That’s because the hand sanitizers you purchase in the store are correctly formulated with more science than simply mixing a little water, aloe, and essential oils, according to Consumer Reports. If you can’t get your hands on the real stuff, then simply wash your hands with soap and water. Plus, regular hand sanitizer doesn’t last as long as you think.

Skip: Vodka

Pass on the vodka (for cleaning purposes, at least). While alcohol in the percentage range of Isopropyl will do the job nicely, vodka is no match for the coronavirus. Tito’s Vodka even tweeted advice: “Per the Center for Disease Control and Prevention, washing hands with soap and water is the best way to get rid of germs in most situations. If soap and water are not readily available, you can use an alcohol-based hand sanitizer that contains at least 60 percent alcohol. Tito’s Handmade Vodka is 40 percent alcohol, and therefore does not meet the current recommendation of the CDC.” Next, check out our coronavirus cleaning guide.

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