Deuteranopia
Green-BlindDeuteranopia is the most common type of dichromatic color vision deficiency. It occurs when the medium-wavelength (M) cones, responsible for perceiving green light, are completely absent or nonfunctional. People with deuteranopia have difficulty distinguishing between reds and greens, though unlike protanopia, they do not experience the characteristic darkening of the red spectrum.
Prevalence (Men)
~1.2% of men
Prevalence (Women)
~0.01% of women
Affected Cones
M-cones (medium-wavelength, green-sensitive) are absent
Colors Commonly Confused
Green and red
Green and brown or tan
Blue and purple
Pink and gray
Orange and yellow-green
What Is Deuteranopia?
Deuteranopia is a form of dichromacy in which the retina lacks functional medium-wavelength (M) cones. These cones normally respond most strongly to green light at around 530 nanometers. Without them, the visual system processes color using only the long-wavelength (L) and short-wavelength (S) cones. The resulting perception reduces the full-color spectrum into a palette dominated by blues and golds, with reds and greens becoming nearly indistinguishable from each other.
How Deuteranopia Affects Vision
Unlike protanopia, deuteranopia does not cause a significant loss of perceived brightness across the spectrum. Reds still appear reasonably bright, but greens tend to look beige, tan, or brownish. The confusion between red and green is the hallmark feature, making it difficult to tell a red rose from its surrounding green leaves, for example. The mid-spectrum colors, including greens, yellows, and oranges, tend to collapse into similar-looking tones. Blues and purples can also be confused because the ability to distinguish blue-shifted greens from blue-shifted purples is diminished.
Causes and Genetics
The genetic basis of deuteranopia lies in the OPN1MW gene cluster on the X chromosome. Human color vision evolved through duplication of an ancestral cone opsin gene, and the red and green opsin genes sit adjacent to one another. This tandem arrangement makes them prone to unequal recombination during cell division, which can delete the green opsin gene entirely. Deuteranopia can also arise from point mutations that render the M-opsin protein nonfunctional. In rare instances, acquired deuteranopia can occur due to optic nerve disease, retinal toxicity from medications, or age-related changes in the lens and retina.
Diagnosis
The Ishihara color plate test is the most widely used screening tool and is effective at detecting deuteranopia. Because the Ishihara test cannot distinguish between deutan and protan deficiencies on its own, additional testing with an anomaloscope or arrangement test like the Farnsworth D-15 may be required for a precise classification. Computer-based color vision tests, such as the Cambridge Colour Test, offer quantitative assessments that can map the specific axis and severity of color confusion.
Living with Deuteranopia
Deuteranopia is a lifelong condition, but it rarely limits a person's overall quality of life. People with deuteranopia often develop an intuitive understanding of which colors they confuse and learn to use alternative cues. For instance, they may judge traffic lights by position and context rather than color. Digital tools have made everyday navigation easier, and workplace accommodations are increasingly common. Many people discover they have deuteranopia only during routine screenings, having unconsciously adapted to their color perception throughout childhood.
When to See a Doctor
A color vision evaluation is recommended for any child entering school, as undiagnosed color blindness can lead to frustration with color-dependent lessons in art, science, and geography. Adults who have always had difficulty with reds and greens may benefit from a formal diagnosis to access workplace accommodations and assistive technology. Any sudden or progressive change in color perception, especially if accompanied by other visual symptoms such as blurred vision or visual field loss, should be evaluated promptly as it may indicate an underlying medical condition.
Genetics & Inheritance
Deuteranopia is caused by mutations or deletions in the OPN1MW gene on the X chromosome (Xq28), which encodes the green-sensitive opsin protein. It follows an X-linked recessive inheritance pattern. The OPN1MW and OPN1LW genes are arranged in a tandem array on the X chromosome, and unequal crossing-over during meiosis can lead to deletion of the green-opsin gene. This is why green-cone deficiencies are the most common form of color vision deficiency.
Daily Life Impact
Distinguishing between green and red indicators on electronic devices, dashboards, and status lights is challenging.
Identifying the ripeness of fruit and vegetables such as bananas and tomatoes is often unreliable by color alone.
Reading color-coded subway or transit maps can be confusing when lines use red and green.
Nature-related activities like hiking or gardening may be affected because greens and browns blend together, making it harder to distinguish foliage from soil or bark.
Interpreting color-coded data in charts, heat maps, or educational materials often requires additional context.
Tips & Adaptation
Enable color-blind modes available in modern operating systems, browsers, and applications to shift problematic colors into more distinguishable ranges.
When creating or requesting documents, ask for redundant coding such as patterns, icons, or text labels alongside color.
Use a digital color identifier app on your smartphone for tasks like matching paint colors, sorting laundry, or choosing ripe produce.
Establish a clothing organization system with labeled sections so you can quickly identify complementary outfits.
At work, let colleagues know about your color vision so they can consider accessibility when designing presentations and dashboards.
Frequently Asked Questions
What is the difference between deuteranopia and deuteranomaly?
Deuteranopia is the complete absence of M-cones, resulting in dichromatic vision with only two functioning cone types. Deuteranomaly is the milder, more common form in which M-cones are present but have a shifted spectral sensitivity, resulting in anomalous trichromatic vision. People with deuteranomaly can still perceive some green tones but with reduced accuracy, whereas people with deuteranopia cannot distinguish green wavelengths at all.
Is deuteranopia more common than protanopia?
Yes. Deuteranopia affects approximately 1.2% of men compared to about 1% for protanopia. When you include the anomalous forms (deuteranomaly at ~5% of men and protanomaly at ~1% of men), deutan deficiencies are by far the most prevalent type of color vision deficiency. This is partly because the green opsin gene is more susceptible to deletion through unequal recombination due to its position in the gene cluster.
Can deuteranopia affect career choices?
Some professions have color vision requirements that may exclude people with deuteranopia. These include commercial airline piloting, certain military roles, maritime navigation, and some electrical trades where wire color coding is safety-critical. However, the majority of careers are fully accessible, and many fields, including software development, have become increasingly conscious of designing for color accessibility. It is worthwhile to research specific career requirements early if you have deuteranopia.
Do color-filtering glasses work for deuteranopia?
Color-filtering glasses, such as those made by EnChroma, work by selectively filtering wavelengths of light to increase the contrast between red and green signals reaching the eye. They can be helpful for some people with deuteranomaly (the anomalous, milder form) where M-cones are present but shifted. For deuteranopia, where M-cones are entirely absent, these glasses are generally less effective because there are no green-sensitive cones to stimulate. Individual experiences vary, and a trial is recommended.
Related Types
Deuteranomaly
Green-WeakDeuteranomaly is the most common form of color vision deficiency, affecting approximately 5% of men worldwide. It is a type of anomalous trichromacy in which the medium-wavelength (M) cones are present but have a shifted spectral sensitivity, peaking closer to the long-wavelength range. This reduces the ability to distinguish between greens, reds, and yellows, though most people with deuteranomaly retain functional color vision and may not even realize they perceive colors differently.
Protanopia
Red-BlindProtanopia is a type of red-green color blindness in which the long-wavelength (L) cones in the retina are completely absent or nonfunctional. People with protanopia cannot perceive red light, causing reds to appear dark or nearly black and making it difficult to distinguish between reds, greens, and browns.
Protanomaly
Red-WeakProtanomaly is a mild form of red-green color blindness in which the long-wavelength (L) cones are present but have a shifted spectral sensitivity, peaking closer to the medium-wavelength range. This anomalous trichromacy results in reduced ability to distinguish between reds and greens, though the effect is generally less severe than in protanopia. People with protanomaly can still perceive red but see it as less vivid and somewhat shifted toward green.
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