Published by ColorVision Editorial Team. This educational content is not individual medical advice. Read our editorial policy and test methodology.
Quick answer
Deuteranopia is a red-green colour vision deficiency caused by absent M-cones. It can make reds and greens harder to distinguish, but unlike protanopia it usually does not make reds appear unusually dark; a browser activity cannot diagnose it.
Deuteranopia: Green Colour Blindness Explained
Deuteranopia is a form of colour vision deficiency caused by the complete absence of M-cones (medium-wavelength sensitive cone cells). It is classified as red-green colour blindness and is one of the most common forms of CVD. People with deuteranopia are sometimes described as green-blind.
Key Facts
- Prevalence: ~1% of males; under 0.01% of females
- Most common severe form of red-green CVD in males
- Cause: Absence of M-cones; X-linked recessive inheritance
- Key difference from protanopia: Red objects retain normal brightness (no luminosity reduction)
How Deuteranopia Affects Vision
With only L-cones and S-cones functioning, deuteranopes perceive colour along a limited axis. Specifically:
- Red and green appear very similar — both may look brownish, yellowish, or tan
- Red and yellow may be confused with certain shades of green
- Purple appears as blue (since the green component of purple is absent)
- Unlike protanopia, red objects do not appear darker — this is the key clinical distinction
The colours that remain clearly different are those along the blue-yellow axis. Blues and yellows remain relatively distinct, while the red-green portion of the spectrum collapses.
Deuteranopia vs. Deuteranomaly
| Deuteranopia | Deuteranomaly | |
|---|---|---|
| M-cones | Absent | Present, shifted |
| Severity | More severe | Usually mild–moderate |
| Prevalence | ~1% of males | ~5% of males |
| Vision | Dichromacy | Anomalous trichromacy |
Deuteranomaly is the single most common form of colour blindness, affecting ~5% of males. It involves M-cones that are present but shifted in their peak sensitivity toward the L-cone range. The result is reduced but not eliminated ability to distinguish red from green.
Inheritance
Like protanopia, deuteranopia follows an X-linked recessive inheritance pattern. The responsible gene is OPN1MW on the X chromosome.
- Colour-blind father + non-carrier mother → daughters are all carriers; no sons affected
- Carrier mother + unaffected father → 50% of sons colour-blind; 50% of daughters are carriers
Diagnosis
Conventional Ishihara editions contain printed plates used by professionals to screen for red-green differences, while controlled tools such as an anomaloscope may be used for classification. ColorVision’s digit plate activity uses original browser-generated plates; it is not the 38-plate clinical edition and cannot diagnose deuteranopia.
Frequently Asked Questions
Is deuteranopia more common than protanopia? Deuteranomaly (shifted M-cones) is far more common. In terms of complete dichromacy, deuteranopia and protanopia have similar prevalence (~1% each in males).
Can people with deuteranopia drive safely? Yes, in most jurisdictions. Positional cues from traffic lights (top = red, middle = amber, bottom = green) are sufficient. Most countries do not restrict driving licences for standard red-green colour blindness.
Do colour-correcting glasses work for deuteranopia? Some people benefit, though results vary considerably. Filters work by increasing the separation between red and green wavelengths reaching the remaining cones.
Evidence & sources
These sources provide background on colour vision deficiency and conventional clinical testing. ColorVision’s browser-based activities are educational screens, not clinical instruments.
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