Kelly McSweeney

Oct 27th 2021

What Does It Mean to Be Colorblind?


We take it for granted that the sky is blue — but is that a matter of fact or a matter of perspective?

Colorblindness is more common than you might think: About one in 12 men and one in 200 women experience the condition, according to Healthline. A deeper look at what it means to be colorblind can help us better understand the way others see the world, and maybe teach us something about vision itself.

How Vision Works

Vision begins in the retina, which is an important membrane that lines the surface of the back of the eye. The retina is made of several layers of tissue, including a layer of photoreceptors — the specialized cells that absorb light (photons) and convert it into signals that are sent to the brain to create an image.

Scienceline explains that two types of photoreceptors help us see: rods and cones. Rods distinguish between black and white (and help us see in the dark), while cones work in bright light, allowing you to see color. People with normal vision have three types of cones that each detect a certain range of color: red, blue and green. In other words, different types of cones detect certain wavelengths of the visible light spectrum.

Colorblindness, which can also be called color vision deficiency, happens when the pigments in those light-sensitive cones are missing or not working properly. Therefore, when a person has missing or dysfunctional pigments in their retina’s cones, they may perceive colors differently than most people do.

Often, people with colorblindness see colors less intensely and therefore have trouble distinguishing one color from another. In rare cases, people with severe color blindness may not see colors at all, or they could also have symptoms such as involuntary eye movements (nystagmus) or sensitivity to light, according to the National Eye Institute.

Types of Colorblindness

Most people are aware that colorblindness exists, but medical providers can help to diagnose the specific condition so that patients are aware of how their eyes affect their perception of colors. There are four main types of colorblindness. The variety depends on which cones are affected and whether the cones are dysfunctional or missing altogether.

1. Anomalous Trichromacy

People who have anomalous trichromacy have all three types of cones, but one type doesn’t work properly. Most commonly, people have trouble telling the difference between red and green or have trouble seeing the difference between some shades of red, yellow and green. Sometimes, the effects are so mild that people don’t even realize they are colorblind. There are subcategories between different types of red-green colorblindness, according to Healthline.

For example, people with protanomaly have the long wavelength cones (“L” cones), but the cones are dysfunctional, which causes red to look like green. Deuteranomaly, on the other hand, causes the opposite issues; the medium wavelength cones (“M” cones) of the eye are dysfunctional, causing green to look redder.

2. Dichromacy

While anomalous trichromacy can make it hard to put together a puzzle or coordinate an outfit, dichromacy is a more serious version of color blindness. People with this condition don’t just have dysfunctional cones. Rather, they are lacking a type of cone altogether, which means they can’t see an entire section of the rainbow.

3. Monochromacy

In monochromacy, two of the three cone types are missing. This rare condition can cause people to see mostly blurry images in black, white and shades of gray. According to MedlinePlus, not only do people who have blue cone monochromacy see fuzzy colorless images, but they also experience sensitivity to light (photophobia), nystagmus and nearsightedness (myopia).

4. Achromatopsia

Complete colorblindness, also called achromatopsia, is a rare disorder in which all the cones are either missing or dysfunctional. In this case, people who are colorblind experience a complete lack of color vision, plus additional vision problems. (Note: Some experts consider blue cone monochromacy to be a form of achromatopsia because it involves vision impairment.)

What Causes Colorblindness

Most forms of colorblindness are genetic. In other words, most people who are colorblind inherited a gene for the condition from their parents. The genes associated with colorblindness are recessive and carried on the X chromosome, according to Scienceline, which explains why this condition is more common in males. Females typically have two X chromosomes, so even if they have a recessive colorblind gene, their other dominant gene can override it. However, males usually have only one X chromosome, so if they inherit the gene, they will be colorblind.

Specifically, MedlinePlus explains that mutations in the OPN1LW, OPN1MW and OPN1SW genes cause color blindness. Genetic changes involving any of these genes can lead to an absence of cones or to the production of abnormal pigments or defective cones.

Although most colorblindness is genetic, it can also be caused by damage to the eye or the brain. Colorblindness has been linked to:

  • Alcoholism

  • Congenital diseases

  • Cataracts

  • Side effects of medicine (such as chloroquine, which is used to treat malaria)

  • Diseases involving the retina

  • Exposure to toxic chemicals, such as organic solvents

Outlooks and Treatments

Most of the time, colorblindness is mild and not considered a disability. It is a common condition, especially among white men. There is no cure, but according to NEI, most people who are colorblind are able to adjust and don’t have problems with everyday activities.

Treatments can include special eyewear that can help individuals differentiate colors. There are also apps where people can take pictures to identify colors. Plus, depending on what causes colorblindness (such as a side effect of a medicine), it could be temporary. Emerging gene therapy research could also provide some new ways to treat colorblindness.

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