Deutan color blindness, also known as deutanomaly or green-weakness, is one of the most common forms of color vision deficiency. It is an inherited condition that affects around 1% of men and 0.01% of women globally. People with deutan color blindness have difficulty distinguishing between green, red, and yellow shades.
What is deutan color blindness?
Deutan color blindness is a type of red-green color vision deficiency caused by an anomaly in the M cone photoreceptors in the retina. Humans typically have three types of cone cells that are each sensitive to different wavelengths of light and enable normal color vision – short (S), medium (M), and long (L).
In people with deutan color blindness, the M cone photoreceptors detect a shifted range of wavelengths, resulting in difficulty distinguishing between colors that primarily stimulate the M cones. This includes colors in the green, yellow, orange, and red range. The S cones and L cones generally function normally.
What causes deutan color blindness?
Deutan color blindness is a genetic condition passed down on the X chromosome. Genes for the M cone photoreceptors are carried on the X chromosome. Males only have one X chromosome, while females have two. This is why deutan color blindness is much more prevalent in men.
Since the condition is recessive, females need two affected X chromosomes to be deutan colorblind while males only need one. If a female inherits one affected X chromosome, she will be a carrier of the condition but typically unaffected. She has a 50% chance of passing on the affected gene to her sons who will be colorblind, and 50% chance of passing it on to her daughters who will be carriers.
Prevalence of deutan color blindness
It is estimated that around 1% of men and 0.01% of women have deutan color blindness. This means it affects around 1 in 100 males and 1 in 10,000 females globally. The high prevalence in males is due to it being inherited on the X chromosome.
The rates do vary between populations however, with higher rates reported in males of European descent and lower rates in males of African descent. This is likely related to genetic differences between ancestral populations.
Types of deutan color blindness
There are two main types of deutan color blindness:
- Deuteranomaly – This is the most common type affecting over 5% of European males. It is characterized by a shifted M cone sensitivity towards the red end of the spectrum. This makes it difficult to distinguish between reds, greens, and yellows.
- Deuteranopia – This rarer severe form affects around 1% of European males. It involves missing or non-functional M cones, leading to an inability to perceive green light and see reds as dull.
In both types, purples may also appear more blue, and it becomes hard to tell the difference between blue/purple and pink shades.
Signs and symptoms
People with deutan color blindness do not see the world in black and white. However, they do have difficulty determining shades in the red-green range. Here are some of the most common signs and symptoms:
- Unable to discern shades of green, red, orange, yellow, brown
- Purple, violet, lavender, and pink can be confused
- Certain reds may appear more brown or green
- Grass appears more yellow/tan than green
- Trouble differentiating blue from purple and dark pink
- Ripe tomatoes appear orange rather than red
- Less able to differentiate colors in dim lighting
- May have trouble identifying colors like orange, brown, teal, mauve
The severity can range from mild difficulties in the deuteranomaly form, to complete inability to see reds in deuteranopia. Most people compensate well and may not even realize they have a color vision deficiency until tested.
How deutan color blindness is diagnosed
Diagnosing deutan color blindness typically involves specialized vision testing by an ophthalmologist or optometrist. They will carry out one or more of the following assessments:
- Ishihara test – This test uses circular dot patterns made up of various colors. Numbers or shapes made of dots a different shade are embedded within the patterns. People with normal color vision can discern the shape or number while those with color blindness cannot.
- Farnsworth D-15 – The person is asked to arrange a set of colored caps in order from light to dark. Specific errors indicate deutan color blindness.
- Anomaloscope – This device mixes red and green light beams. The person adjusts the mix until the light appears pure yellow, allowing the examiner to determine cone sensitivity.
- Genetic testing – This looks for known gene mutations causing deutan color blindness.
These specialized tests can determine the type and severity of deutan color blindness. Basic vision screening using color plates and warning lights cannot accurately diagnose deutan color blindness.
How does the world look to someone with deutan color blindness?
The world appears visibly different to people with deutan color blindness. They have trouble discerning shades in the green to red range that are obvious to people with normal color vision. Here are some examples of how everyday things may look:
| Object | Normal color vision | Deutan color blindness |
|---|---|---|
| Ripe tomatoes | Red | Orange or brown |
| Grass | Green | More yellow or tan |
| Tree leaves | Green | Less vibrant green |
| Purple flowers | Purple | Blue |
| Pink shirt | Pink | Grey or beige |
| Orange | Orange | Yellow/brown |
| Red traffic light | Bright red | Muted or greyed out |
| Rainbow | All colors visible | Mostly yellow/blue with faded middle |
As seen above, the red-green range is typically desaturated and shifted. Purples often appear more blue, while pinks can look grey or beige. Oranges lose vibrancy and look brown. Grass, leaves, and other green foliage appears yellow, tan or faded.
Compensating for color blindness
While there is currently no cure for inherited deutan color blindness, there are ways those affected can better navigate a colorful world:
- Use color identifiers like labels or swatches when accuracy is important
- Rely more on shades like dark vs light rather than colored nuances
- Enhance reds and greens on digital screens and displays
- Avoid careers like electrician or pilot that rely heavily on color
- Learn alternative cues like texture, pattern, shape, or location
- Ask others to identify ambiguous colors as needed
- Wear tinted lenses or glasses with color enhancing filters
- Use apps that convert images to deutan-friendly palettes
New assistive technologies are also being developed, like Oxy-Iso lenses that enhance red-green contrast for wearers. Increased awareness and accommodations for color blindness is improving accessibility in modern life.
Impacts of deutan color blindness
Although deutan color blindness is not debilitating, it can lead to some difficulties navigating daily tasks with color cues:
- Trouble reading colored graphs, charts, diagrams
- Difficulty interpreting meters and warning lights
- Challenges ripping foods, judging produce ripeness
- Issues discerning colors in art, nature, cosmetics
- Problems with sports like tennis where the ball color matters
- Difficulty distinguishing colored wires and electronics
- Inability to fully enjoy colorful sunsets, fall foliage
- Reduced color matching ability in fashion, decor
This can lead to embarrassment, confusion, or even dangers like misreading indicators. Many occupations like electrician, pilot, graphic designer require normal color vision. However, with minor adaptations and increased awareness, deutan color blindness can be worked around well in most careers and daily life.
The use of color coding as the sole means of conveying information should always be avoided as it excludes those with color deficiencies. Adding symbols, patterns, labels, or other visual cues along with color ensures accessibility for all.
Raising awareness of color blindness
While color blindness is relatively common, there are still misconceptions and lack of general knowledge on the topic. Here are some ways to raise further awareness:
- Promote color vision screening in schools and workplaces
- Include information on color blindness in educational materials
- Train designers, employers, educators on colorblind friendly practices
- Share inclusive design tips like avoiding color-only cues
- Celebrate annual Color Blindness Awareness Month in March
- Feature the experiences of those with color deficiencies
- Advocate for increased color blindness research
- Use badges, pins, ribbons showing colorblind support
With improved understanding and adaptations, people with all types of color vision can thrive. Minor steps go a long way in ensuring color blindness is no longer an obstacle in modern society.
Conclusion
Deutan color blindness involving altered green perception affects up to 1% of males. Those affected have difficulty differentiating shades in the red-green-yellow spectrum. While not completely color blind, the world appears muted and shifted in hues of red, purple, pink, orange and green. With simple adaptations like labels, filters, and enhanced awareness, deutan color blindness can be effectively managed.
