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How Do You Know If You're Color Blind?

VO: Noah Baum WRITTEN BY: Mark Sammut
Millions of people around the world are color blind. Are you one of them? While color blindness presents itself in various different ways, all types of the condition are defined by one thing - a mixing of some colors, and a complete inability to perceive others. It's all caused by optic abnormalities within your eye, which mean that your brain process light differently. You can be born with color blindness, or it can develop over time - but it's typically very difficult to diagnose.
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How Do You Know If You’re Color Blind?


What is color blindness? Despite the condition's name, "blindness" is arguably not an accurate descriptor, as it suggests an outright inability to observe an object. And that’s not really the case. Let's assume someone never sees red; color “blindness” might imply an apple would lose any color whatsoever or would be straight up indiscernible. In reality, the fruit should look perfectly normal, but the hue would lose some of its brightness, perhaps coming across as a dull brown or yellow. This condition refers to a difficulty in distinguishing colors, primarily: red, green, and blue. And the symptoms tend to be so subtle, that many people go through their entire lives without even realizing that an apple should be red.

So, why is color blindness even a thing? In order to properly answer that question, let’s first look at the biological process governing the perception of color. This might seem like an obvious point, but sight depends entirely on light. Be it artificial or natural; objects reflect light into our eyes and stimulate photo-receptors known as cones, which then send the information to our brains. On average, a human possesses around six million of these cells in one eye's retina, and cones are split into three groups that react vigorously to a specific wavelength. Studies have discovered that more than 60% of cones prefer red, while around 30% opt for green, and 2% only spring to life when blue is in the room. The red, green, and blue then mix together to allow other shades to be perceived. Your average retina also contains around 120 million rods, which are a type of receptor dealing with black and white. While good to know about, rods aren’t really relevant to color blindness.

Inconsistencies arise due to not everyone holding all the necessary pigments to view the entire spectrum of colors. Trichromacy applies to anyone with normal vision, but some retinas are deficient in one color or another. Rather than a color-blind person possessing fewer cells, research suggests it’s more due to the cones simply not being as sensitive as they should be.

As with most conditions, color blindness comes in many forms. Anomalous trichromacy is the most common type and refers to a retina which is less receptive than normal to a particular wavelength. In milder cases, the differences could be barely detectable, but distinguishing certain tones becomes a genuine struggle as we move up the spectrum.

Depending on the culprit, anomalous trichromacy is divided into three subcategories: protanomaly for red, deuteranomaly for green, and tritanomaly for blue. Out of the three, green is the most common, while blue is quite rare. Any shades associated with the impacted light will take on a distinct look, but it varies depending on the severity. In general, a reduced sensitivity to red or green tends to impact purple, brown, and orange.

When a retina completely lacks the ability to recognize a light wavelength, this is known as dichromatic vision and occurs when one of the cone types is entirely absent. As with anomalous trichromacy, dichromacy is split into three types, with red and green being the most common. Even if – for example – the cones related to red are missing, this does not mean the other colors are not impacted, as many people struggle to accurately spot green and vice-versa. While not usually life-threatening, dichromacy impacts many aspects of everyday life, including something as basic as being able to tell if food is well-cooked or rotten.

Last and the least common, monochromacy is the only subset of color blindness that lives up to its name: anyone with this type views the world in shades of gray. At most, an object's brightness might indicate its associated color, but differentiating shades would not really be possible. Alongside its rarity, monochromacy is the simplest to self-diagnose, meaning people experiencing it almost always ‘know’ about it.

How widespread is color blindness? Estimates suggest the condition affects around 8% of men and less than 1% of women. This means one in every twelve men should be color blind, while the ratio shoots up to around one in 200 for women. Clearly, gender plays a significant role, but why is there such a gigantic discrepancy? In short, the answer comes down to genetics.

A person's DNA make-up is determined by genes located in 23 pairs of chromosomes, with the last one determining the sex. Women have two X chromosomes, while men possess an X and a Y. Color blindness mutates the X chromosome, but this gene needs to be passed down by both parents for their daughter to be affected, so many women end up acting as carriers. On the other hand, boys who inherit the trait will always be color blind. Even if neither parent is diagnosed, their child is not necessarily in the clear.

Besides the genetic lottery, color vision deficiency can be a symptom of a broader condition, including Parkinson's disease and cataracts. Aging can also diminish the retina's sensitivity.

For the sake of argument, let's assume neither parent is actively color blind; What early symptoms should they look out for? An inability to distinguish between red and green toys or stationary would be the most obvious sign, but color-blind children also tend to compensate with a heightened sense of smell. A preliminary and straightforward test would be to fill a paper with a wide range of colors and ask the child to replicate them. If the task proves difficult, it might be time to visit an ophthalmologist for a formal diagnosis.

If, for one reason or another, visiting a doctor isn’t an option, there are ways to check from the comfort of your own home. Many websites use a variant of the Ishihara deficiency test, which presents the participant with numerous plates covered by colored dots. Certain entries will contain a number or line that is only visible to people with “good” vision, while the reverse holds true for a handful of the other slides. Split into 38 plates and giving around three seconds per entry, the Ishihara test determines whether someone struggles with specifically red or green, and how severely.

Another popular experiment was created by Dean Farnsworth and involves arranging 100 hues with minor deviations into a pattern to determine whether the participant can spot the differences. The original test was split into four patterns and could be used to diagnose any type of color blindness, although detecting weaker forms proved to be an issue.

Even though the online versions of both tests are popular and quite helpful, the results can be skewed by a monitor's resolution, lighting, and gamma settings. Ultimately, going to a specialist is the only way to accurately be diagnosed, but there’s probably no need if the online tests return a positive result.

At the moment, there is no cure for inherited color blindness. As advancements continue to be made in genetic therapy this may change in the future, but identification and adaptation will always be the most important steps. Schools also need to be informed, as teachers need to take measures so that children don't miss out on any important information due to the way it is presented. And, if color vision deficiency is a symptom of another condition and not genetic, then opticians might be able to administer a treatment – or refer you to someone who can. Obviously, this needs to be taken on a case by case basis, though.
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