Deuteranopia, commonly known as deutan color blindness, is a type of red-green color blindness where the green photoreceptors in the eyes do not detect light.
What is deutan color blindness?
Deuteranopia is one of the most common types of color blindness, affecting around 1% of males and 0.01% of females. It is an X-linked genetic condition, meaning it is passed on through the X chromosome. Females need two affected X chromosomes to be deutan colorblind, while males only need one.
Individuals with deuteranopia lack functioning M cones, which are the photoreceptor cells in the eye that detect green light. This makes it difficult to distinguish between reds, greens, browns, oranges, and yellows. These colors all appear more muted or washed out.
What colors do deutans have trouble distinguishing?
Since deutans lack working green photoreceptors, they struggle to tell apart colors along the red-green color spectrum. However, they can usually distinguish between blue and yellow hues.
Here are some common colors deutans have trouble differentiating:
- Green and red
- Green and brown
- Blue and purple
- Green and orange
- Pink and gray
- Teal and gray
While deutans can see these colors, they appear duller and less vivid. The colors often blend together, making it hard to discern subtle shade variations.
How do deutans see the world?
To understand how the world appears to someone with deutan color blindness, it helps to visualize the effects:
- Greens, reds, oranges, and browns all lose their brightness and become desaturated.
- Purple shifts toward blue tones.
- Pink takes on a more grayish tone.
- Turquoise and teal appear duller and more gray.
- Yellow stays bright.
- Blue remains vivid.
While deutans can still see a wide range of colors, the world looks less vibrant and saturated. Certain reds, greens, and oranges are almost indistinguishable from shades of brown or gray.
Effects on everyday life
Deuteranopia can make many daily tasks more challenging:
- Driving – Traffic lights can be confusing, and it may be hard to spot brake lights or signs.
- Cooking – Determining if meat is cooked, or telling when fruits and vegetables are ripe can be difficult.
- Shopping – Clothing colors like pink, purple, green, and orange are tough to discriminate.
- Nature – The bright colors of flowers, plants, and fall foliage appear washed out and less vibrant.
- Art – Many paintings and color photographs are more difficult to appreciate.
Fortunately, there are ways to manage deutan color blindness in everyday situations, which will be covered later in this article.
Degrees of deutan color blindness
Deuteranopia exists on a spectrum from mild to strong:
- Mild deutan – A slight red-green color confusion, but most shades can still be differentiated.
- Moderate deutan – More significant difficulty discerning red-green hues, with washed out appearance.
- Strong deutan – Very strong red-green color confusion, with many shades appearing similar.
Those on the mild end of the spectrum may not even realize they have any color vision deficiency. But as deutan color blindness increases in severity, it becomes more difficult to tell apart certain hues from white, black, or grey.
Why deutans can’t distinguish red and green
To understand why deutans have trouble with greens and reds, it helps to look at how color vision works in the eyes:
- Cone cells in the retina detect different wavelengths of light.
- S cones detect short blue wavelengths.
- M cones detect medium green wavelengths.
- L cones detect long red wavelengths.
Normal color vision requires all three types of cones. The brain compares signals from the different cones to distinguish a wide range of hues.
In deutan color blindness, the M cones don’t function properly. This makes it impossible to detect green light, or compare green signals to red and blue.
As a result, greens appear more red or brown. Red and green shades bleed together and are virtually indistinguishable in many cases.
Other types of red-green color blindness
While deutans lack working green photoreceptors, there are two other forms of red-green color blindness:
- Protanopia – Lacking working red cones. Reds appear dark, and red/green confusion.
- Tritanopia – Lacking working blue cones. Blues appear greenish, and blue/yellow confusion.
Protanopia is less common than deuteranopia, affecting around 1% of males and 0.01% of females. Tritan color blindness is very rare.
Color blindness diagnosis
Deuteranopia and other color vision deficiencies can be detected through several different tests:
- Ishihara plates – Colorful dot plates that form a number visible to those with normal color vision.
- Farnsworth D-15 – Arrange 15 colored caps in hue order.
- Anomaloscope – Match red/green or blue/yellow light mixes.
- Genetic testing – Identify color vision gene mutations.
These tests can determine the type and severity of color blindness. They may be administered by an optometrist, ophthalmologist, or other vision care specialist.
Managing deutan color blindness
While there is currently no cure for inherited deutan color blindness, there are ways to minimize the impact on daily life:
- Use color identification apps or charts.
- Label clothing tags with color names.
- Have others confirm colors when uncertain.
- Rely more on brightness, saturation, and context.
- Learn to identify when ripe fruits/vegetables.
- Use a thermometer when cooking meat.
Special color-enhancing glasses may also be an option. While they don’t correct the underlying deficiency, they can make certain hues appear brighter and easier to differentiate.
Color blind-friendly design
When designing websites, apps, infographics, maps, etc. there are tips to make them deutan/color blind friendly:
- Avoid conveying info with only red & green.
- Use highly saturated colors.
- Include symbols with colored elements.
- Use patterns & textures, not just color coding.
- Allow user customization of color palettes.
Following accessibility guidelines and testing with color blind users helps ensure that designs don’t exclude people with color vision deficiencies.
Genetics of deutan color blindness
Deuteranopia is passed on genetically through the X chromosome. It is a recessive trait, meaning both parents must carry the affected gene for a son to inherit deutan color blindness. Here are some key genetic factors:
- Caused by mutations in the OPN1MW gene that codes for M opsin.
- Located on the X chromosome at Xq28.
- Affects males much more than females.
- Mothers are often carriers of deutan color blindness.
- Females need two affected X chromosomes to be deutan.
Genetic screening can identify female carriers and their risk of passing deutan color blindness to future sons. Prenatal testing is also available to determine if a fetus is color blind.
| Color | Appearance to Deutan |
|---|---|
| Red | Darkened |
| Green | Desaturated brown or red |
| Orange | Desaturated red or brown |
| Brown | Dull, flat brown |
| Pink | Light gray |
| Purple | Blue |
| Yellow | Bright yellow |
| Blue | Vivid blue |
Conclusion
Deuteranopia is a common form of red-green color blindness where the green photoreceptors in the eyes malfunction. This makes it hard to tell apart reds, greens, oranges, and browns, which all appear dull or desaturated.
While there is no cure, there are effective ways to manage deutan color blindness through color aids, careful labeling, and color blind-friendly design. Understanding the limitations of color vision can help create more accessible environments for the color blind community.
