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The Many Shades of Color Blindness

February 15, 2021

Being colorblind can mean a lot of different things, yet only in rare cases does it mean seeing in black and white.

The technical term for complete color blindness is monochromacy, and it only affects one person in 33,000. Most people with a form of color blindness can see certain colors, but which ones and why depends on a few factors. Let’s take a closer look at the different types of color blindness.

How Does Color Vision Work?

Two crucial pieces of the biology of human eyesight are the rods and cones in our retinas. These are specialized cells that can detect light. Rods are good at detecting contrast in the intensity of light, but only cones can detect differences in color.

A person with normal color vision has three types of cones that absorb light at three different wavelengths. There are cones for short (blue) wavelengths, medium (green) ones, and long (red) ones. Remember what old TV sets looked like up close, with tiny red, green, and blue phosphors that work together to produce all the colors in an image? It’s a little like that.

Genetics and Color Vision

An important gene that enables us to see color is located on the X chromosome, which means that women have two copies of the gene but men only have one. Because the gene is recessive, a woman can have one copy of the gene for color blindness without it impacting her vision. Her sons, however, have a fifty percent chance of being colorblind, depending on which of her X chromosomes they get.

The daughters of a colorblind man will at least be carriers of the color blindness gene, unless they get a second one from Mom. This is why roughly one man in every dozen is colorblind but only one in every two hundred women is.

Different Types of Color Blindness

There’s basically only one way for color vision to go right (trichromacy), but many ways it can go wrong. People with anomalous trichromacy have all the cones, but some of them misfire, producing a similar outcome to dichromacy (two-cone color vision).

The most common form of color blindness is red-green, and it could be because the green cones aren’t working (deuteranomaly) or the red cones aren’t working (protanomaly). In both cases, the result is a dull landscape of brownish-yellows. This is the type of color blindness that affects more men than women.

Blue-yellow color blindness (tritanopia) doesn’t come from the X chromosome, so it’s evenly distributed between the sexes. When the blue cones don’t work properly, the result is a palette of pinks, teals, and browns. Tritanopia only accounts for 5% of all cases of color blindness.

As we touched on earlier, the rarest form of color blindness is monochromacy, and it can happen because no cones work, just one type works, or there’s a problem with the way the visual cortex in the brain processes the images from the retinas. Monochromacy also tends to come with weak central vision, severe light sensitivity, and involuntary eye movements.

Is Color Blindness Treatable?

You might have heard of the sunglasses that enable colorblind people to see in the full spectrum of colors for the first time in their lives. Those sunglasses are pretty amazing, but they don’t work on all forms of color blindness. A dichromat (someone who only has two types of cones) wouldn’t get anything from sunglasses like that, but an analogous trichromat might! They have all the cones, but some of them misfire and respond to more wavelengths than they should.

The sunglasses work by blocking out specific wavelengths so that the colors are better separated. It increases the contrast between colors and helps train the cones to respond only to the correct wavelengths. If you haven’t seen the videos of colorblind people trying on those sunglasses for the first time, we definitely recommend checking some out.

Color Blindness Is Something We Check For

If you want to make sure whether or not you’ve been living life in full color, we can test for that in a regular eye exam. Color blindness might seem like a minor issue, but it can make some everyday tasks more difficult. There are resources to help with that, and the first is diagnosis!

Your lifelong vision health is our highest priority!

Top image used under CC0 Public Domain license. Image cropped and modified from original.
The content on this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.

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