Deuteranopia: Green Blindness and Deuteranomaly Explained
Deuteranopia and deuteranomaly affect the cells for green light. Together they are the most common form of color blindness – about three in four people with red-green color blindness have one of them.
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What is deuteranopia?
In deuteranopia the M cones – the cells most sensitive to medium-wavelength, green light – are missing. The name comes from the Greek "deuteros" (second). People see with two instead of three cone types; they are dichromats, just like many mammals, for example dogs.
Deuteranomaly: the milder green weakness
Much more common than deuteranopia is deuteranomaly. Here the green cones are present, but their sensitivity is shifted toward red, so the brain receives a weaker red-green signal. It ranges from barely noticeable to almost as strong as deuteranopia.
| Deuteranomaly | Deuteranopia | |
|---|---|---|
| Green cones | present, shifted | missing |
| Also called | green-weak | green-blind |
| Frequency (men, European descent) | about 5% | about 1% |
| Frequency (women) | about 0.35% | about 0.01% |
Deuteranomaly alone is more common than all other color vision deficiencies combined.
How people with deuteranopia see
- Red, orange, yellow-green and green look similar – yellowish to brownish.
- Brown and dark green, pink and gray, purple and blue are easily mixed up.
- Unlike in protanopia, red does not look much darker.
- Blue-yellow contrasts and brightness differences stay clear.
More examples in what do color blind people see?
Causes and inheritance
The genes for the green pigment (OPN1MW) sit on the X chromosome right next to the red pigment gene. Because these genes are so similar, they can recombine when passed on – creating "hybrid" pigments that cause the shifted sensitivity in deuteranomaly. Green weakness is X-linked recessive, so mostly men are affected. More in red-green color blindness.
Deuteranopia test
An Ishihara test quickly shows whether you have red-green color blindness. Our free online test also tells you whether your answers point to deutan or protan and how strong it is. Whether it is deuteranomaly or deuteranopia can be measured precisely by an eye doctor with an anomaloscope.
Tips for everyday life
- Turn on the "deuteranopia" color filter in iOS or Android accessibility settings.
- In charts and spreadsheets, use patterns or labels instead of red/green only.
- With deuteranomaly, many users report that color blind glasses separate reds and greens more clearly.
Frequently asked questions
What is the difference between deuteranopia and deuteranomaly?
In deuteranopia the green cones are missing; in deuteranomaly they are present but their sensitivity is shifted.
How common is deuteranomaly?
About 5% of men of European descent – it is the most common color vision deficiency of all.
Do dogs see like people with deuteranopia?
Roughly, yes: dogs also have only two cone types and confuse similar colors, though they also see less sharply.