Color blindness is a condition that affects millions of people worldwide: population statistics have shown that up to one in twelve men, and one in two hundred females have a full or partial color vision deficiency, affecting up to 350 million people worldwide. However, despite its prevalence, color blindness is often misunderstood, leading to misconceptions and a lack of awareness about the challenges faced by those who live with it.
I. Introduction
Color blindness, medically known as color vision deficiency (CVD for short), is a condition that alters the way an individual perceives colors. Color blindness is a bit of a misnomer, in fact: in most cases it does not actually consist of any blindness per se, but rather a difference in the way one sees color. In most cases, individuals with CVD have difficulty distinguishing between specific shades of colors, however are able to see normally other, unaffected, shades. Ultimately, there is no one-size-fits-all: the severity and nature of the condition can vary significantly among individuals.
In the following sections, we will delve deeper into the intricacies of color blindness. We will explore the causes of CVD, types of CVD, and how it affects those who live with it. We'll also discuss how it's diagnosed and the tools and strategies that can help individuals manage the condition. Furthermore, we'll look at the exciting research and developments in the field that hold promise for the future!
Whether you're a person living with color blindness, a friend or family member of someone with the condition, a professional encountering color-vision based challenges in the workplace, or simply someone interested in learning more, we hope to bring some new insights to understanding and awareness of the complexities of color vision deficiency.
II. What is Color Blindness?
Color blindness, or color vision deficiency, is a condition that affects the way an individual perceives and distinguishes colors. The nature of this condition can be physical, meaning it is due to a difference in the way the eye absorbs specific frequencies of light, or it can be neurological, meaning it pertains to how color information is processed by the neural cells in the retina and/or the brain. However, it is important to understand that color “blindness” is not a form of blindness, as the name might suggest, but rather a deficiency or difference in the way one sees color.
To understand color blindness, let’s first discuss how normal color vision works. The human eye perceives color through specialized cells in the retina called cone cells. There are three types of cones, each sensitive to different wavelengths of light that correspond to different colors: red, green, and blue. Vision scientists refer to these cone cells not by their colors but actually by the wavelength region of light that approximately corresponds to the colors, specifically: L-cones for long wavelength response (red light), M-cones for medium wavelength response (greenish light) and S-cones for short wavelength light (blue light). When a photon light enters the eye, it has a specific frequency of vibration corresponding to its wavelength. The different types of retinal cone cells are tuned to “bands” of wavelengths and will only absorb a photon with their corresponding bandwidth range. Technically, a single photon can trigger a retinal cone cell to fire, however generally for good color vision to occur, a substantial number of photons need to be received over a region of connected retinal cone cells, enabling subsequent retinal wiring in layers called retinal ganglion cells to perform comparions between the different types of cone cells to determine the relative amount of contribution of each color category.
Most commonly, what we understand as color blindness occurs when one of the types of cone cells in the retina is improperly “tuned” resulting in it absorbing a range of light wavelengths that is different from the normal range. When mis-tuned as such the person may experience a reduced difference in the signals from neighboring retinal cells of different types, which reduces the ability to detect fine differences in color shades over the affected region of the visible spectrum. This is what occurs in the common types of red-green color vision deficiency such as deuteranomaly, deuteranopia, protanomaly and protanopia.
In some other examples, retinal cone cells may be entirely missing, or otherwise unable to absorb light due to pigmentation of the retinal epithelia. This can result in a range of color vision abnormalities from from a slight difficulty distinguishing between certain shades (such as tritanomaly) to a complete inability to perceive color, which is generally referred to as complete achromatopsia or monochromacy.
It's important to note that color blindness is typically caused by genetic factors, meaning that it is a lifelong condition that people are born with. As such, due to neural plasticity, a person with color vision deficiency is usually able to develop sufficient coping strategies to enable them to lead a normal life in spite of their differences. However, color blindness can also develop later in life (also called “acquired CVD”) due to medical conditions or exposure to specific chemicals that can have toxic or neurological effects on the retinal cells. Despite the challenges it can pose, most people with color blindness adapt to their condition and are able to lead normal lives, albeit with a somewhat different visual experience of the world.
III. Causes of Color Blindness
As mentioned previously, the most common types of color blindness are genetic conditions, meaning it is passed down from parents to their children. In common red-green color blindness, affecting 1 in 12 men and 1 in 200 women, the genes responsible for for the L-cone and M-cone retinal cone photopigments are located on the X chromosome. As such, it is an X-linked recessive condition. This is why color blindness is more common in males, who have only one X chromosome, compared to females, who have two. If a male inherits an X chromosome carrying the color blindness trait from his mother, he will be color blind. However, for a female to be color blind, she must inherit the trait from both her mother and father. Over multiple generations, this type of color vision deficiency is passed down through the matriarchal side of a family.Other, less common, types of color blindness can also be inherited, such as types of achromatopsia caused by a mutation at the CNGA3, CNGB3, GNAT2, PDE6C, or PDE6H genes. Achromatopsia follows an autosomal recessive inheritance pattern. The particular CNGB3 mutation was popularized by the Oliver Sack’s book, “Island of the Color Blind”.
However, as we are by now aware, color blindness isn't necessarily inherited. In some cases, it can be an acquired condition, meaning it develops later in life as a result of chance, or environmental factors, or age. Some factors that can lead to acquired color blindness include:
- Age: As people age, the clear lens and the cornea in the eye can yellow and darken, altering color perception. The yellowing of the lens initially causes blue colors to be more difficult to see, and is called tritanomaly (an anomaly of the third cone type, the S-cone). As it progresses, the lens may begin to cloud resulting in cataracts requiring surgical intervention to treat.
- Illness: Certain diseases can affect color vision, including diabetes, glaucoma, macular degeneration, Alzheimer's disease, Parkinson's disease, and leukemia, among others. Some illnesses can affect the retinal cells of the eyes, while others may affect the nerves and the ability of the eye to relay information to the brain through the optic nerve.
- Medications: Some medications, including specific antibiotics, blood pressure medications, and drugs used to treat psychological disorders, can also affect color vision. If you think your vision is being affected by a medication, please consult a doctor for assistance!
- Chemical Exposure: Exposure to certain chemicals, particularly in the workplace, can lead to color vision deficiency. Industrial solvents are a common source of such chemicals – if you work with these, take the ventilation requirements seriously!
In cases of acquired color vision deficiency, the severity of the condition can vary over time. That is why it's important to have regular eye examinations that include a color vision sensitivity test, especially if you have a condition or are taking a medication known to affect color vision.
IV. Types of Color Blindness
In the field of vision science, and more specifically color vision science, it is preferred to use the terminology “color vision deficiency” rather than the more common “color blindness”. The more technical terminology is preferable because it avoids some of the misconceptions and confusions implied by the word “color blind” (which, in addition to being an inaccurate description, can also be confused with the unrelated socio-political use of the term). Regardless, we may continue to use the word “color blindness” herein for convenience and common understanding.
Color blindness (or color vision deficiency) can vary in type and severity, with some individuals having trouble with only certain, specific colors, while those with a strong or severe condition may not perceive colors at all. The types of color blindness include the following:
- Protanomaly and Protanopia: A type of genetically inherited red-green color blindness, characterized by a mutation of the red-sensitive photopigments corresponding to the long-wavelength sensitive L-cone retinal cells. It is important to note that a person with protanomaly or protanopia does in fact have normally functioning L-cones, however what is not normal is the wavelengths of light they respond to. Individuals with protanomaly have a reduced sensitivity to red light. Reds and oranges may appear duller and less bright. Colors with a red component such as purple, may appear to be blue. In the more severe condition known as protanopia, the L-cone spectral response overlaps entirely, or nearly entirely, with the green-sensitive M-cone spectral response, causing a total inability to differentiate between colors along the protan confusion line. Red appears as dark brown or black, and certain shades of orange, yellow, and green all appear identical to brown or yellow. Around 25% of cases of genetically aquired color vision deficiency are in the Protan family (protanomaly = mild to moderate, protanopia = severe).
- Deuteranomaly and Deuteranopia: This is the most common type of color blindness by the numbers, making up nearly 75% of all cases. The condition is caused by a mutation of the green-sensitive photopigment found in the medium-wavelength M-cone retinal cells. Usually, deuteranomaly is a mild condition and doesn't interfere with daily living. Deuteranopia, however, is caused by a total overlap between the green and red photopigment responses, causing a total inability to discriminate between colors along the deutan confusion line. Many shades of red look brownish-yellow, and shades of green can be confused with beige, sometimes in surprising ways such as commonly seen-as brown peanut butter appearing to have a greenish tinge.
- Tritanomaly and Tritanopia: Usually these conditions are types of acquired color vision deficiency associated with aging of the eyes (yellowing of the lens), chemical exposure, or medical conditions such as diabetes. Tritanomaly is characterized by a reduced sensitivity to blue light, making blue appear greener and darker. Tritanopia, a very rare form of color blindness, is characterized by the inability to perceive blue light.
- Monochromacy and Achromatopsia: These are the most severe forms of color blindness, but fortunately, are also quite rare. Monochromacy, also known as total color blindness, is a condition in which two or all three of the cone cells are absent, causing individuals to see only in shades of gray. Common forms include S-cone monochromacy (having only S-cones) and rod monochromacy (having no retinal cones and relying only on rods, i.e., night vision, to see). Usually, achromatopsia is a non-progressive and hereditary visual disorder. However in the case of certain diseases such as retinitis pigmentosa, it can be a progressive loss that increases over time.
- General Loss of Chromatic Sensitivity: Perhaps one of the least understood forms of color vision deficiency, a general loss of chromatic sensitivity is characterized by a non-specific reduced sensitivity to variation in color. Non-specific meaning that the confusions are not confined to a particular confusion line in color space. The general loss of chromatic sensitivity can occur as a result of neurological trauma or developmental problems, however the exact causes can be highly specific to an individual’s medical history and, as such, are beyond the scope of the present discussion.
Each of these types of color blindness presents its own unique challenges and requires different strategies for management. However, with understanding and the right tools, individuals with color blindness can navigate the world effectively.
V. How Color Blindness Affects Vision
Color blindness is not just a matter of seeing or not seeing certain colors – more broadly, it influences how an individual perceives and interprets the world around them. Our vision does not function like a camera taking a picture, rather, the eyes collect information sporadically from various points in our environment, and then a substantial amount of higher order processing occurs to stitch these glances together into a coherent estimate of the visual scene. When someone has color blindness, what they notice and how they see it can differ substantially from someone with normal color vision. These differences may also depend on the type and severity of color blindness.
For instance, in common types of red-green color blindness such as deuteranomaly and protanomaly, the ability to distinguish between reds, greens, and in some cases, yellows is affected. For someone with this condition, a traffic light might look completely different. The "red" stop signal may appear to be a dull, brownish-red or even a dark gray, while the "green" go signal might look white or light yellow. This can make tasks like driving more challenging, as the color cues we often take for granted aren't as clear.
Similarly, imagine looking at a rainbow, a phenomenon that's typically a vibrant display of distinct colors. For a person with normal color vision, a rainbow consists of up to six separate hues organized into “bands” of light: red, orange, yellow, green, blue, and violet. However, for someone with red-green color blindness, the rainbow might only consist of two apparent bands: yellow and blue. Not nearly as interesting!
In another example, vision may be affected when color is a primary distinguishing feature of objects that are small, distant, or surrounded by specific textures or lighting conditions that can cause the object boundary to be obscured. A common example is when a person with color vision deficiency does not notice brightly colored red flowers on a bush – they might just blend in with the leaves and become invisible. Sometimes, a colored object can become visible but only when the person directs their vision in a narrow “cone” of attention directly at a location. Certain color vision tests, such as the Ishihara plate test, are based on this exact type of “invisibilty cloaking” of color – the dappled light pattern used in the dots of the test requires one to use a wider field of view to appreciate the hidden number, and makes it impossible to “zero in” on a specific color difference anywhere in the image to solve the puzzle.
Interestingly, in some cases having a color vision deficiency can actually enhance color vision – specifically, for people with deuteranomaly, theory predicts a slight improvement in the ability to differentiate between shades of blue and green, due to an increased separation of the S-cone and M-cone photopigment spectral sensitivity. Unfortunately, these gains are offset by a proportional loss of ability to discriminate between green and red shades. However, in the case of protananomaly, no such gains are predicted as all of the cone cells have increased overlap and an overall narrowing of the spectral sensitivity window is experienced.
Tritan-type CVD, or blue-yellow color blindness, affects the ability to distinguish between blues and greens, primarily, and the ability to see differences between dark blues and other dark shades such as gray and black. When caused by a yellowing of the lens, an individual with tritanomaly may also experience issues with circadian rhythm desynchrony due to a weak signaling of the time of day to the photo-sensitive ipRGC cells, responsible for synchronizing the body’s clock to the cycles of daylight.
In the rare cases of total color blindness or achromatopsia, individuals see the world in grayscale, much like a black-and-white photograph or film. Achromatopsia and monochromacies are also often associated with an extreme sensitivity to bright light. This can make it challenging to interpret visual information that relies heavily on color, and generally to navigate in the world. Extremely dark sunglasses may help someone to better control the glare of bright lights.
It's important to note that while color blindness can make certain tasks more difficult, most people with the condition adapt and find ways to differentiate colors that look similar. For example, they might rely more on texture, brightness, or position rather than color alone. Therefore, color blindness (except in extreme cases) is typically classified as a mild disability.
VI. Diagnosis of Color Blindness
The need to perform a diagnosis of color blindness typically is encountered in either an academic or professional context. In academics, it is important to diagnose children with potential color vision deficiency, to ensure they receive adequate support in the classroom to ensure success. In some professions, diagnosis of color blindness is a mandatory step due to job performance requirements, such as in mission-critical operations of equipment commonly found in first responders and the military.
Several tests can be used to identify color vision deficiencies, each with its own unique approach. The choice of which test is used varies widely, and unfortunately, has not been standardized well across many industries. Some of the most commonly encountered tests include:
Ishihara Plate Test: This is the most commonly used test for diagnosing red-green color blindness, however is also considered to be somewhat archaic by current standards – being based on an over 100-years old design. The test consists of a series of plates, each containing a circle of dots appearing randomized in color and size. Within the circle of dots, a number is embedded in a certain color, while the surrounding dots are colored with a complementary shade that falls on one of the chromatic confusion lines corresponding to a type of color blindness. Individuals with normal color vision can distinguish this number. However, those with a color vision deficiency may not see the number or may see a different number.
Anomaloscope: Considered the “gold standard” in color vision science, but due to cost and difficulty of operation, is rarely used. This test asks individuals to match colors using dials that control the brightness and color of two different light sources. The anomaloscope is particularly useful for obtaining the best possible accuracy in diagnosing red-green color blindness and determining its severity.
Farnsworth-Munsell 100 Hue Test: This test is designed to detect more subtle color vision deficiencies, and is often used in the graphic design and print production industries to measure fine color vision. It involves a set of colored caps or panels that need to be arranged in order of hue. The test can be time-consuming, and requires administration under a properly controlled light source.
Cambridge Colour Test: This is a computer-based test that uses the concept of color confusion lines to detect, classify, and quantify color vision anomalies. It's similar to the Ishihara Plate Test but can provide more detailed information.
HRR Pseudoisochromatic Plate Test: This is another plate test, similar to the Ishihara test but with an improved, modern design, that can be used to detect both red-green and blue-yellow color blindness. It's often used as a quick screening tool in eye clinics however it is also adept at determining the severity of a deficiency. The HRR test uses basic symbols such as square, circle, triangle and “X” shapes rather than numbers or letters.
These tests are typically performed by an optometrist, or an optometric assistant. In pediatric optotometry, routine color vision screening is recommended to catch undiagnosed cases in children. Routing screening for tritanomaly may also be incorporated into opthamology treatment centers specializing in care of glaucoma, macular degeneration and diabetes. If you suspect that you have a color vision deficiency, it's important to get tested as a color vision test may not always be performed in routine eye care. Understanding your color vision can help you develop strategies to manage color blindness in daily life and can also inform career choices, as certain jobs require accurate color perception.
VII. Living with Color Blindness
Living with color blindness can present a number of challenges that across various aspects of daily life, from simple tasks like choosing ripe fruit at the grocery store or cooking a steak to the desired level of doneness, to more significant issues like interpreting traffic signals or data visualizations at work. However, the good news is that individuals with color blindness often develop strategies to compensate for their color vision deficiency, and there are numerous aids and tools available to assist them.
One of the primary challenges is working with visual information where color differentiation is crucial. For instance, in certain professions like graphic design, electrical work, or aviation, accurate color perception is essential. In these cases, individuals with color blindness may need to rely on labeling, coding systems, or assistance from colleagues, or could be excluded from working in that profession.
In everyday life, tasks such as cooking, shopping, or coordinating clothing can also be challenging. However, people with color blindness often develop unique strategies to compensate. For example, they might organize their clothing by outfit rather than color, or they might rely on texture, firmness and smell when selecting produce.
There are also various aids and tools designed to assist people with color blindness. Special corrective lenses, both for glasses and contact lenses, can enhance color perception for certain types of color blindness – however, it is important to note that results are highly variable and substantial controversy exists regarding the usefulness of many of these products. In theory, these lenses work by filtering out specific wavelengths of light, enhancing the contrast between different colors, however doing so generally comes at the cost of a reduction in the ability to discriminate between other colors. Ultimately, the usefulness of such lenses is highly specific to both the individual and the color discrimination task.
Digital apps can also be a useful tool. These apps use the camera on a smartphone or tablet to provide color identification, helping individuals with color blindness differentiate colors more easily. Some apps can even customize the color palette on the device's display to make it more accessible, however these may cause undesirable side effects such as causing an inaccurate appearance to colors or reducing the differences between other colors.
In addition, many digital platforms and software now offer color vision deficiency modes, which adjust the colors used in graphics and displays to make them more distinguishable for individuals with color blindness – however, there is no broad consensus regarding how such modes should work, and little in the way of research to show that they are effective.
VIII. Current Research and Future Possibilities
The field of color vision science research is a relatively small area of vision science today, but is nonetheless continuously evolving, with scientists and researchers around the world working to better understand this condition and develop effective treatments. While there is currently no cure for inherited color blindness, several promising areas of research could change this in the future.
One of the most exciting areas of research is gene therapy. Gene therapy aims to treat color blindness by introducing a normal version of the mutated gene into the affected cells of the retina. In one proposed method, a retrovirus carrier is responsible for conveying the corrected genes using an intravitral injection. In laboratory settings, this approach has successfully restored color vision in monkeys. For the case of certain types of severe color vision loss associated with achromatopsia, gene therapies have been successfully deployed in human subjects – however, are extremely expensive and still not suitable for broad adoption by the millions of people living with more mild forms of color blindness.
Another promising development, as discussed previously, is the use of color filtering lenses. These lenses, which can be used in glasses or contact lenses, work by filtering out specific wavelengths of light, enhancing the contrast between different colors. Historically, this approach has suffered from the problem that any enhancement of color contrast in one region of the spectrum is matched by a proportional decrease in color contrast in a complementary region of the spectrum. However, modern lens designs are able to use more selectively absorbing dyes that reduce the magnituted of this problem.
Researchers are also exploring the potential of augmented reality glasses that use active optics to enhance color perception. These could someday enable a relatively seamless integration of software applications that identify and/or transform confusing colors into our everyday life through a pair of smart glasses.
While these developments are promising, it's important to note that they are still in the early stages of development and have not yet scaled to the point where the vision of the millions of people living with color blindness can be sure to find help. However, they represent a significant step forward in the quest to fully understand, mitigate, and potentially cure color blindness.
IX. Conclusion
In wrapping up this exploration of color blindness, we should step back for a moment to appreciate that this condition presents a unique way of perceiving the world. If there is one takeaway we hope everyone can remember, it is that color blindness is not simply a matter of seeing the world in grayscale, but rather experiencing colors in a different way. This can range from a slight difficulty distinguishing between certain shades to a complete inability to perceive color, but usually falls somewhere in the middle.
While it can pose certain challenges, we should also appreciate that our ability to adapt to differences in perception serve as a powerful testament to the diversity of human experiences, the adaptability of individuals living with color vision deficiencies and the potential for those who see the world differently to not just survive but to thrive.
Color blindness, both in inherited or acquired forms, affects a significant portion of the population: some estimates begin at 350 million people, but could be much higher after including the growing aging populations affected by aquired tritanomaly.
For anyone suspecting they might have a color vision deficiency, it's highly recommended to get tested – perhaps initially with a free online color vision test, and ideally with a clinicially administered test under proper conditions to ensure an accurate diagnosis. Early and accurate diagnosis can help individuals understand their condition, learn coping strategies, and make necessary adjustments in their daily lives and careers.
Beyond the individuals directly affected, knowledge and understanding of color blindness are crucial for the broader society. It's important for educators, employers, designers, and policymakers to be aware of color blindness in order to create inclusive products and accessible environments. This can involve simple adjustments like using color-blind friendly palettes in visual materials, to providing clear labeling and coding systems, or making digital platforms sufficiently customizable to ensure accessiblity to those with color vision deficiencies.
In the realm of scientific research, the future holds promise. With ongoing studies in gene therapy, new lens technologies, and augmented reality smart glasses, there's hope for even more tools and treatments that can assist those with color blindness.
In essence, understanding color blindness is a step towards a more inclusive and empathetic society. We hope that by dedicating a small portion of our awareness to this condition, the world will take a small but necessary step toward acknowledging the diversity of human experiences and ensuring that everyone, regardless of how they perceive color, can fully engage with the world around them.
X. References
National Eye Institute. (2019). Facts About Color Blindness. Retrieved from https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/color-blindness
American Academy of Ophthalmology. (2020). What Is Color Blindness? Retrieved from https://www.aao.org/eye-health/diseases/what-is-color-blindness
NIH Genetics Home Reference. (2021). Color Vision Deficiency. Retrieved from https://ghr.nlm.nih.gov/condition/color-vision-deficiency
National Health Service. (2018). Colour Vision Deficiency (Colour Blindness). Retrieved from https://www.nhs.uk/conditions/colour-vision-deficiency/
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