Color blindness is a particular condition characterized by the difficulty or inability to perceive certain colors properly. It doesn't necessarily mean seeing the world in black and white, but rather having specific difficulties distinguishing between certain colors or shades.
Why does color blindness appear?
The main cause of color blindness is a genetic mutation that affects the retinal cones, the cells responsible for color perception. Red-green color blindness (the most common, accounting for 99% of cases) is a condition linked to the X chromosome. This is why it affects men much more. In fact, around 8% of men have some form of color blindness and only 0.5% of women are color blind.
How do we perceive colors under normal conditions?
The light stimulus is received by the cones, which are light-sensitive cells located in the retina of the human eye and responsible for color vision. There are only three types of cones in the retina and each one has a different sensitivity to colors: L cones (capture long wavelength light - the color red), M cones (capture medium wavelength light - the color green) and S cones (capture short wavelength light - the color blue). The stimuli are fed to the brain, which doesn't just see the colors in isolation, but compares and mixes them to create the perception of different colors.
This comparison and mixing of colors is done with the information that comes from the simultaneous activation of the red and green cones (red-green axis activation), and the simultaneous activation of the 3 types of cones (blue-yellow axis activation). Thus, in the activation of the red and green cones (L and M), if both cones are activated at similar intensities, the brain perceives yellow. In blue-yellow axis activation, the brain compares the signals from the S (blue) cones against the combined signals from the L (red) and M (green) cones. If the S cones are strongly activated and the L+M cones are less activated, the color will be blue. If all 3 are activated equally, the color is white or gray.
And how do colorblind people perceive colors?
Color blind people perceive colors differently due to the absence or deficiency of the cells (cones) responsible for capturing light. This affects the chromatic axes and changes the way colors are interpreted by the brain.
In alterations to the red-green axis (L and M cones - Red and Green), L cones may be absent and red is perceived as black or brown, green may appear grayish or yellow and purple may appear blue because the red component is missing. If there is only a deficiency (and not a complete absence) of L cones, red is still perceived, but weaker and less vibrant, and can be mistaken for brown, orange or green. In the absence of M cones, which are responsible for green, this color disappears or appears as brown or beige, and red can appear yellowish or grayish. Shades close to green can be mistaken for brown or dark red. If there is only a deficiency in the M (green) Cones, green is still perceived, but weaker and yellowish. Shades of red may appear less intense or mixed with brown.
On the Blue-Yellow axis (S - Blue cones), if there are no S cones, the color blue disappears or appears green/grey; yellow can appear white and the sky can appear greyish or greenish. If there is only a deficiency of S cones, blue is perceived, but weaker and less vibrant. Some colors that mix blue (such as purple) may appear redder.
What limitations can color blindness cause?
Most colorblind people have a mild form and can live normally, with minor adaptations in everyday life. In fact, around 99% of color blind people have red-green color blindness and 75% of these have a mild form, being able to distinguish some colors, but having difficulty with close shades.
There are, however, professions in which these limitations can have an impact and even be a hindrance, such as navy pilots, air traffic controllers, airline pilots, professional drivers, electricians or designers. In everyday activities, there may be difficulties in choosing clothes, reading road signs or other situations that depend on clearly distinguishing colors and which are more or less significant depending on the degree of impairment in the functioning of each of the cells.
In general, these limitations do not compromise other visual abilities. However, when only one type of cone works or when none of the three work, there can be a severe decrease in visual acuity and marked limitations in daily activities, including the absence of reading and driving vision.
Is color blindness curable? Are there strategies to overcome color blindness?
There is no cure for this condition. However, there are several strategies that can help colorblind people cope with their limitations. Examples include:
- Use of cell phone applications and software that, through cameras, help identify colors (e.g. Color Blind Pal, Color Grab or EnChroma applications);
- Special glasses can improve color perception in some cases;
- Use of high contrasts, symbols or labels to help identify colors in the workplace, in teaching or even when selecting the color of clothing;
- Learn techniques for associating colors with names, objects or functions. For example, the sky is blue, the grass is green and the sun is yellow. Even if the color-blind person doesn't see these colors correctly, they can memorize that specific objects have certain fixed colors.
In short, color blindness is a condition that affects around 8% of men and 0.5% of women and in 99% of cases affects the perception of the red-green axis. Although they see the world differently, and despite difficulties in some day-to-day activities and specific professions, most people with color blindness adapt well, being able to use technology, visual strategies and learning, minimizing the challenges and enabling a full and functional life.