With or without colors: how do colorblind people see?

2024-04-21 05:30:00

As a reminder, color blindness is dyschromatopsia, i.e. a color perception disorder linked to damage to the photoreceptor cones of the retina of the eye. “It is most often hereditary or congenital, but it can also be acquired and occur without any family history following a mutation or an eye disease,” specifies Dr. Zwillinger.

At the risk of surprising you, color blind people can therefore see in color. However, depending on the degree of damage and the type of photoreceptors affected, they may have difficulty distinguishing certain shades or fully perceiving the difference between certain colors. In very rare cases, some people are nevertheless unable to discern colors and see in black and white…

Color blindness: how do color blind people see?

The cones of the retina are none other than the cells that allow us to distinguish colors. There are three categories of cones: cones sensitive to short wavelengths (most sensitive to blue light), cones sensitive to medium wavelengths (most sensitive to green light) and cones sensitive to long wavelengths (most sensitive to red light).

Concretely, when light hits the retina, the cones react to different wavelengths of light by sending electrical signals to the brain via the optic nerve. The brain then processes these signals to form a colorful image of our surroundings and allow us to distinguish all shades of blue, green and red.

In the case of color blindness, one or more cones may be altered or completely absent. In fact, the information transmitted to the brain is biased, which causes difficulty in perceiving certain colors. Dr. Marie Seminel, retinologist.

The vision of men and women suffering from color blindness does not change over time…

As Dr. Zwillinger explains to us, congenital and hereditary color blindness are bilateral, symmetrical and non-scalable. In other words, both eyes are affected at the same intensity from birth until death. Once the diagnosis is confirmed, those affected do not need to have their eyesight tested regularly: they instead develop coping strategies to better manage their condition over time. And the expert adds: “Eye fatigue has no impact on color blindness, but ambient brightness can slightly influence the distinction of contrasts.”

Good to know : so-called aftereffect color blindness (which occurs following optic neuropathy or acquired maculopathy) can change and get worse over time. In this case, we are interested in the origins of color blindness to better manage it, underlines the expert.

Colorblind people are not more exposed to ENT disorders!

No, colorblind people are not more likely to develop a vision disorder like astigmatism, hyperopia or myopiaanswer the experts.

Protanopia, protanomaly, deuteranopia, deuteranomaly, tritanopia… Several “visions” of color blindness

Color blindness affects approximately 8% men and 0.45% women. That said, there are different “types” of color blindness, or rather different degrees of impairment.

There are three types of abnormal trichromatism (when people have three types of cones, but one of them malfunctions);

the protanomaliecharacterized by partial damage to the red L cones, sensitive to long wavelengths; deuteranomalycharacterized by partial damage to the green M cones, sensitive to medium wavelengths; tritanomaliecharacterized by partial damage to the blue S cones, sensitive to short wavelengths.

There are three types of dichromatism (when people have only two types of cones that work):

the protanopiecharacterized by the absence or total damage of red L cones, sensitive to long wavelengths; deuteranopiacharacterized by the absence or total damage of green M cones, sensitive to medium wavelengths; tritanopiecharacterized by the absence or total damage of blue S cones, sensitive to short wavelengths.

In certain cases, only one type of cone works: we speak of monochromatisme. And much more rarely, none of the cones work, which completely prevents color perception: we are talking aboutachromatism.

It is important to quickly know which cones are affected, to be able to quickly direct children towards specific treatment to alleviate their dyschromatopsia. That said, some people are affected very heavily and others very lightly, to the point where they don’t even know they are colorblind. Dr. Stéphanie Zwillinger, ophthalmic surgeon.

Ultimately, what colors do we see when we are colorblind?

As you will have understood, the way in which color blind people perceive colors depends on the type of cones involved and the severity of the damage.

People with protanopia see the world in a restricted range of colors, mainly composed of blue, green and yellow. Reds are seen as shades of dark gray or black. Greens may appear paler or appear like light gray tones. Yellows can look very similar to whites or light grays.People with protanomaly have reduced sensitivity to red color wavelengths. They often confuse green and red: red colors may appear paler or less vibrant, and shades of green may be difficult to distinguish from reds. Some tones of purple may also appear similar to blues, and some tones of brown may appear similar to greens.People with deuteranopia have difficulty distinguishing red from green. Greens can be seen as shades of beige or gray. Reds can be perceived as shades of brown or gray.People with deuteranomaly have reduced sensitivity to green-colored wavelengths. They often confuse green and red: greens may appear less vibrant or appear more yellowish, and reds may appear darker or more brown. Some shades of brown may appear similar to greens, and some shades of red may appear similar to browns.People with tritanopia have difficulty distinguishing blue from green and yellow. Blues may appear to be shades of green or gray. Yellows may appear to be shades of pink or gray. Bright, saturated colors may appear dull or desaturated.People with tritanomaly have reduced sensitivity to blue color wavelengths. They often confuse blue and green, as well as certain shades of yellow. Blues may seem less vibrant or appear greener, and yellows may seem less intense or appear fainter. Shades of purple may appear similar to blues, and shades of green may appear similar to blues or yellows.

This can cause many difficulties in daily life. Colorblind people may, for example, have difficulty interpreting road maps or traffic lights, choosing matching clothes or identifying certain nuances in a work of art, for example.

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Tested and approved: for a realistic simulation, download the application Chromatic Vision Simulator (available on the Play Store and App Store)!

Do some colorblind people really see in black and white?

Some people do see the world in black and white. due to a rare medical condition, achromatopsia. Indeed, men and women suffering from achromatopsia are completely incapable of perceiving colors – and this due to genetic abnormalities affecting the cones responsible for color perception. But let’s be clear, this condition is extremely rare!