Color blindness, also known as color vision deficiency, is the inability to differentiate between certain colors. It can range from mild to severe, and while some see only black, white, and shades of grey, most experience a more mild form of colorblindness in which they can see a limited range of hues (Fallon). Depending on the severity of a person’s color blindness, they may have difficulty distinguishing between the colors of a traffic light or determining the ripeness of fruit. It may also prevent them from having professions in which perceiving color is important to the job, such as being a pilot (“Color Blindness,” National Eye Institute). These impairments are not detrimental, however, and many have adapted around them. As there are different types and varying ranges of color blindness, color blind people don’t see the world in the exact same way as others and are each impacted differently. The passing down of genes is the main cause of color blindness. While there is no cure for color blindness, there are methods that diagnose and help colorblind individuals adapt to the condition.
Types of Color Blindness
Red-green color blindness is the most common type of color blindness. It affects 7% of the male population and 0.4% of the women population in the U.S. (Fallon). Those with red-green color blindness mainly have difficulty telling the difference between red and green. Deuteranomaly, which makes shades of green look more red, is the most common form of red-green color blindness. Another form, protanomaly, makes shades of red look more green. Both are mild forms of color blindness. Protanopia and deuteranopia, however, are more severe forms that result in the complete inability to differentiate between reds and greens (“Types of Color Blindness”).
Blue-yellow color blindness is less common, occurring in fewer than 1 in 10,000 people around the world. Despite its name, people with blue-yellow color blindness confuse blue with green and yellow with red. Those with tritanomaly have difficulty distinguishing between the mentioned colors, while those with tritanopia cannot distinguish between the colors at all (“Types of Color Blindness”).
Figure 1: This figure shows how the views of individuals with different types of color blindness compare with that of normal color vision (Simulation of Different Color Deficiencies, Color Blindness).
Achromatopsia—when someone sees only black, white, and shades of grey—is the rarest type of color blindness, despite it being what some perceive color blindness as. It occurs in about 1 in 30,000 people. Those with achromatopsia cannot see or distinguish between any colors and only perceive black, white, and shades of grey (“Types of Color Blindness”).
The type of colorblindness is dependent on the affected photoreceptor cells in the eyes, which are each responsible for sensing wavelengths of light and distinguishing red, yellow, or blue light. When a certain type of photoreceptor cell, called cones, is absent or altered, a person’s perception of color is affected (Turbert). For instance, the absence of L cones, which are sensitive to red light, correlates to protanopia and results in the inability to perceive the color red. More mild forms of color blindness result when cones are faulty.
Figure 2: This diagram shows the effects of the absence of different cones on color vision (“Types of Colour Blindness”).
Color blindness is also linked to genetics and is passed down through genes. Mutations in certain genes cause the absence or alteration of cones, resulting in color blindness. This hereditary connection can also be seen through the disparity between men and women with red-green color blindness. The genes connected with red-green color blindness are on the X chromosome, which males have one of and females have two of. Only one X chromosome with the gene connected to red-green color blindness is needed for a male to be red-green colorblind. For females, both X chromosomes must have the gene (“Causes of Color Blindness”). This explains the drastic difference between the 7% of men and 0.4% of women in the U.S. that are red-green color blind and the hereditary nature of color blindness.
Color blindness can also be caused by diseases or injuries. Alzheimer’s disease, glaucoma, and leukemia are some chronic illnesses that may lead to color blindness. Damage to the retina of the eye or the brain can also result in acquired color blindness (Fallon).
Diagnosis and Treatment
Specific tests exist to identify color blindness. One example is the Ishihara Test, which is made up of eight plates. Each plate contains colored dots, and in the center of the plate is a number made up of dots that are a different color than the background. Someone with normal color vision is able to identify the number in the center. An individual with red-green or blue-yellow color blindness will see a different number, as they will see the colors and numbers outlined by the dots differently. The Ishihara Test is one of the more well known of many color blindness tests, which distinguishes and helps diagnose those with color blindness (Fallon).
Figure 3: This figure shows how individuals with different types of color blindness may perceive a plate from the Ishihara Test.
There is no cure for color blindness, but many have adapted to their color blindness by using color cues and other details. Eyeglasses that correct color blindness have also been developed. These eyeglasses filter out wavelengths of light, preventing the overlap of wavelengths that causes colors to look similar or be hard to differentiate for color blind individuals (Fallon).
Despite the common misconception of color blind people seeing just black and white, the majority of those with color blindness have a different type of color deficiency with varying degrees of severity. Many have difficulty distinguishing between certain colors rather than a complete loss of color vision. The main cause of color blindness is the passing down of genes, and while there is no cure for the condition, many eventually adapt to their color blindness. Another option for those with color blindness may lie in color correcting eyeglasses. These eyeglasses serve as proof of the understanding that has been gained on color vision deficiency, one that is important to know and that will hopefully become widespread to counter misconceptions about color blindness.
Michelle Li, Youth Medical Journal 2021
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