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Color vision deficiency, or color blindness, is far more likely to affect men than women, as a genetic mutation on the X chromosome is the most common cause. However, women are still affected by all types of color blindness, just at a lower rate.
Red-green and monochromatic color blindness are more likely to affect men. Because blue-yellow color blindness is not carried on the X chromosome, men and women are impacted at the same rate.
Some genetic mutations mean that about 12 percent of women may see more colors, as they are tetrachromats. No men so far have been found with this mutant cone.
While many types of color blindness have a genetic cause, some diseases or exposure to toxic chemicals can trigger color blindness, which may impact women more than men in some cases.
How Genetics Determine Color Blindness
It is well known that color vision deficiency, commonly called color blindness, affects a certain percentage of men. Women can also be color blind, although this is a much rarer occurrence.
Different types of color blindness affect men and women at different rates as well. Generally, about 0.5 percent of women overall are affected by any type of color blindness.
Genetic variations cause color blindness in both men and women. These genetic differences change how the rods and cones of the retina function to absorb and transmit light. Rods provide vision in low-light conditions, like night. Cones are associated with color vision, so many forms of color blindness are caused by genetic changes to the cones.
Three types of cones — green, red, and blue — send signals through the optic nerve to the brain, where the information is processed into a color image. If there is damage or variances in the cones, they will not function normally, and this can cause many types of color blindness.
Types of Color Blindness & Their Frequency in Women
There are three basic types of color blindness, which impact both men and women, although men tend to be affected more.
Red-green Color Blindness
This is the most common form of color blindness, in which the cones in the retina do not process the difference between green or red. This may mean one color is a different shade than the other or that both colors are muted.
Red-green color blindness affects 1 in 12 men of Northern European descent and 1 in 200 women of this descent. People with non-Caucasian ethnic heritage are far less likely to have this type of color blindness. The genes associated with red-green color blindness are passed through the X chromosome.
Blue-yellow Color Blindness
This type of color vision deficiency is rarer. Symptoms include trouble distinguishing dark blue from black and telling the difference between purple, blue, and green shades.
This impacts about 1 in 10,000 people around the world, but it appears to affect men and women equally. There is also no distinction in prevalence between people of different ethnic origins. Since this form of color blindness is passed down on a different chromosome than the X, it impacts all genders equally.
Blue Cone Monochromacy
This is the least common form of color blindness, and it means that the person cannot see any colors at all. While only about 1 in 100,000 people worldwide has monochromacy, men are much more likely to have this condition compared to women; however, there is no difference based on race or ethnicity.
People with this form of color blindness are also likely to have other vision problems, including light sensitivity (photophobia), rapid back-and-forth eye movements (nystagmus), and nearsightedness (myopia).
Some Women See More Colors
In 2012, scientists at Newcastle University reported finding a woman who could see 99 million more colors than the average person. This woman was called a tetrachromat, as she was believed to have an additional type of cone that could perceive subtleties in color much better than trichromats, which is how most people’s cones are arranged.
Since that evidence, it is believed that more women are tetrachromats than men. Current estimates suggest about 12 percent of women have this genetic difference. Some studies attempting to identify tetrachromats examined whether women had the “mutant” cone or not and then asked questions about variations in colors.
A related follow-up study aimed to understand the heredity of color blindness. It found that women with the mutant cones who had color blind sons did not perceive more colors. It was believed that the mutation in one of the X chromosomes may have inactivated the mutant cone.
Causes of Color Blindness Are Not All Genetic
Most types of color blindness are caused by genetic variations, which are more likely to impact men than women. Because women typically have two X chromosomes, the chances for some genetic conditions is lower as there is essentially a backup set of chromosomes. However, women are carriers for many genetic variations that cause color blindness in men. If you are curious whether you are a carrier for color blindness, you can get a genetic test.
There are other types of nonhereditary color blindness that can impact any gender. For example, diseases that damage the retina and the optic nerve can lead to acquired color vision deficiency. This condition can also be a side effect of some drugs, such as those that treat malaria. Exposure to toxic chemicals can also damage the eyes and lead to acquired color blindness.
Some diseases like Alzheimer’s disease, age-related macular degeneration (AMD), diabetes, and multiple sclerosis (MS) increase the risk of developing color blindness. More women are impacted by AMD and MS, while men and women have roughly the same incidence of Alzheimer’s and diabetes. Cataracts can also affect how light enters the eye, which may change how you see color.
There is no cure for color blindness, but it can be managed to a degree. There are some options for treatment, including visual aids or special glasses that help them comprehend the difference between colors so that it’s easier to read, drive, and work on computers.
If you have a family history of any diseases associated with color blindness, take medications that may cause color blindness, or have been exposed to chemicals that may cause damage to the eyes, work with an ophthalmologist to reduce your risk of eye damage. It is also important to work with a general practitioner to manage any underlying conditions like MS or diabetes that can contribute to color blindness.
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