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.
Prevalence (Men)
~5% of men
Prevalence (Women)
~0.35% of women
Affected Cones
M-cones (medium-wavelength, green-sensitive) are present but have shifted spectral sensitivity
Colors Commonly Confused
Green and yellow-green appear similar
Red and orange-brown can be confused
Light greens and tans or beiges
Purple and blue when the red component is subtle
Pastel greens and pastel pinks in soft lighting
What Is Deuteranomaly?
Deuteranomaly is a form of anomalous trichromacy and the single most common color vision deficiency in the world. The M-cones are present and functional but their opsin protein is tuned to respond to slightly longer wavelengths than normal, overlapping more with the L-cone response curve. This means the visual system receives less distinct information from the green-versus-red portion of the spectrum, compressing the range of distinguishable colors in the red-green axis. However, because all three cone types are still functioning, people with deuteranomaly have far better color discrimination than those with deuteranopia.
How Deuteranomaly Affects Vision
The severity of deuteranomaly exists on a spectrum. People with a mild form may only notice color confusion in poor lighting, with small color samples, or when colors are very similar in saturation and brightness. Those with more pronounced shifts may find greens look brownish or yellowish, reds appear somewhat dull, and the distinction between green, yellow, and orange is blurred. Importantly, unlike protanomaly and protanopia, deuteranomaly does not cause a significant luminosity loss, so colors appear at normal brightness even if their hue is perceived differently.
Causes and Genetics
The genetic basis of deuteranomaly lies in hybrid genes created by recombination between the adjacent OPN1MW and OPN1LW genes on the X chromosome. These hybrid genes produce opsin proteins with spectral sensitivities intermediate between normal M-opsin and L-opsin. The high frequency of deuteranomaly in the population is thought to reflect the evolutionary instability of the tandem gene arrangement, which facilitates frequent unequal crossing-over events during meiosis. Multiple hybrid gene variants exist, producing a range of severity from barely detectable to nearly as severe as deuteranopia.
Diagnosis
Deuteranomaly is readily detected by Ishihara color plates, which are specifically designed to identify red-green confusion. To distinguish deuteranomaly from deuteranopia, an anomaloscope test is used. People with deuteranomaly require less green (more red) in the red-green mixture to match a yellow reference, but they have a narrower matching range than dichromats, confirming the presence of anomalous trichromacy. Online color vision tests can provide a preliminary indication but should not replace professional assessment for a definitive diagnosis.
Living with Deuteranomaly
Because deuteranomaly is so common, awareness and accommodation have improved substantially in recent years. Most digital platforms now offer color-blind accessibility settings. Many people with deuteranomaly live entirely normal lives and consider their color vision simply a different but equally valid way of seeing the world. The condition does not worsen over time and does not affect overall visual health. Some researchers have even suggested that anomalous trichromats may have advantages in certain visual tasks, such as detecting camouflaged objects, because they are less distracted by surface color differences.
When to See a Doctor
A formal diagnosis is recommended for anyone who consistently has difficulty identifying or matching colors, particularly in the red-green range. Early screening in childhood is valuable because teachers can adjust instructional methods for children who may struggle with color-coded materials. Adults considering careers with color vision requirements should be tested before committing to training programs. Deuteranomaly itself does not require medical treatment, but a sudden change in color perception at any age should prompt an eye examination to rule out acquired causes.
Genetics & Inheritance
Deuteranomaly is caused by missense mutations in the OPN1MW gene on the X chromosome that shift the spectral sensitivity of M-cone opsin toward longer wavelengths, causing it to overlap more with L-cone opsin. This X-linked recessive condition is so prevalent partly because the M-opsin and L-opsin genes are arranged in a tandem array on the X chromosome, making them prone to recombination events that can produce hybrid genes with intermediate spectral properties.
Daily Life Impact
Greens and yellows can appear very similar, making it hard to tell if a banana is ripe or a traffic light is green versus yellow.
Color-coded data in spreadsheets, charts, and dashboards that rely on red-green distinction can be misread.
Choosing paint colors, decorating a room, or coordinating an outfit may result in combinations that look off to others.
Identifying plants, flowers, and natural features by color can be unreliable, which matters in fields like botany, geology, or landscaping.
Video games and apps that use red and green for team indicators or status markers can be difficult to play without color-blind modes.
Tips & Adaptation
Take advantage of the growing number of apps and games that include color-blind modes, which substitute problematic color pairs with more distinguishable alternatives.
Color-filtering glasses are most effective for deuteranomaly because M-cones are present and responsive; many users report a significant improvement in color richness.
Use browser extensions that adjust website color schemes to be more distinguishable for deutan vision.
In professional contexts, request that reports and presentations use color-blind-safe palettes such as blue-orange instead of red-green.
When precision matters, verify colors with a digital color picker or camera-based color identification tool rather than relying on subjective judgment.
Frequently Asked Questions
Is deuteranomaly really that common?
Yes. Approximately 5% of men of Northern European descent have deuteranomaly, making it by far the most prevalent color vision deficiency. In a classroom of 30 male students, on average one or two will have some degree of deuteranomaly. The prevalence varies somewhat among ethnic groups but remains the most common type worldwide. Among women, the rate is approximately 0.35%, still making it the most common CVD in females.
Can someone with deuteranomaly see any green at all?
Yes. Unlike deuteranopia, in which green cones are entirely absent, deuteranomaly involves green cones that work but are tuned to a slightly different wavelength. People with deuteranomaly can perceive green, but their green perception is somewhat shifted and overlaps more with their red perception. The result is reduced discrimination between greens and reds rather than a complete inability to see green. Many people with mild deuteranomaly perceive grass, trees, and forests as green, just with slightly less distinction between green and neighboring hues.
Will color-filtering glasses cure deuteranomaly?
Color-filtering glasses do not cure deuteranomaly, but they can significantly enhance color discrimination while being worn. They work by placing a notch filter in the part of the spectrum where M-cone and L-cone sensitivities overlap, increasing the effective separation between the two signals. Many users describe the experience as seeing more vivid, distinct colors. However, the effect is only present while wearing the glasses, and the enhanced perception does not carry over to unaided vision.
Can deuteranomaly be mistaken for deuteranopia?
On basic screening tests like the Ishihara plates, severe deuteranomaly can produce results similar to deuteranopia. The anomaloscope test is needed to differentiate the two conditions definitively. This distinction matters because the prognosis and available aids differ. Deuteranomaly, being an anomalous trichromacy, generally offers better color discrimination and responds better to color-filtering glasses than deuteranopia, a dichromacy in which one cone type is entirely absent.
Related Types
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.
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.
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.
Want to test your color vision?