Deuteranopia
(Green-Blind Color Blindness)
Deuteranopia is missing M-cones: red and green collapse toward yellow-brown. It affects about 1% of men; the milder form, deuteranomaly, affects about 5%.
Take the free 18-plate deuteranopia test below (Ishihara-style screening, not a clinic diagnosis).
Free Online Color Blindness Test
Take our free Ishihara color blind test to check for red-green color blindness, deuteranopia, protanopia, and tritanopia. Get instant results with our scientifically-designed 18-plate color vision screening test. No registration required.
- Disable dark mode and blue-light filters (Night Shift, f.lux)
- Set screen brightness to at least 80%
- Ensure you are in a neutral lighting environment
- View screen from a normal reading distance
What Is Deuteranopia?
Deuteranopia is a form of color vision deficiency caused by the complete absence of medium-wavelength (M) cone cells in the retina. These cones are responsible for detecting green light. Without them, the red-green axis of color vision is lost entirely. The partial form is deuteranomaly.
People with deuteranopia cannot distinguish between red and green both colors appear as shades of yellow or brown. Deuteranopia affects approximately 1% of men, while a milder form called deuteranomaly (where M-cones are present but abnormal) affects around 5% of men. Together, these two conditions make deuteranopia-spectrum color blindness the most common CVD worldwide.
Deuteranopia vs. Protanopia
Both are forms of red-green color blindness, but with an important distinction:
- Deuteranopia: Missing M-cones (green). Red and green both shift toward yellow-brown. Brightness perception is relatively normal.
- Protanopia: Missing L-cones (red). Reds appear very dark or nearly black. Overall luminance of the red channel is reduced.
The Ishihara test can differentiate between these two types based on which "hidden" numbers or paths a person can or cannot see.
How Deuteranopia Affects Daily Life
- Traffic lights: red and green look the same (position is used as the cue)
- Food: ripe and unripe fruit are hard to distinguish
- Nature: red berries against green leaves are invisible
- Design: UI errors shown in red against green text become unreadable
- Maps and charts: red/green coding in charts requires additional labels
How to Test for Deuteranopia
The Ishihara test is the most widely used screening tool for red-green color blindness including deuteranopia. Our free 18-plate online test includes plates specifically designed to detect green-axis deficiency.
Designing for Deuteranopia
Since deuteranopia affects ~8% of men, it should be the first CVD type you test for in any design audit. Key guidelines:
- Never use red/green alone to convey success/error states add icons or text labels
- Use the color blindness simulator to preview your UI under deuteranopia before shipping
- Ensure chart colors have sufficient contrast even when red-green distinction is lost
- WCAG 1.4.1 (Use of Color) requires that information is never conveyed by color alone
Prevalence
Deuteranomaly and deuteranopia combined affect approximately 6% of all men and 0.4% of all women. If your product has 1,000 male users, roughly 60 of them have some form of green-axis color blindness.
FAQ
What is deuteranopia?
Deuteranopia is green-blind red-green color blindness—the most common severe red-green CVD, affecting about 1% of men. Medium-wavelength (M) cones are missing.
How do people with deuteranopia see?
Red and green both shift toward yellow-brown. Traffic lights, berries on leaves, and red/green UI states are the usual problem areas. Brightness is closer to typical vision than in protanopia.
How do I test for deuteranopia?
Take the free 18-plate online test on this page. It screens for deuteranopia and related deficiencies in under two minutes.
What is the difference between deuteranopia and deuteranomaly?
Deuteranomaly is partial green weakness (~5% of men). Deuteranopia is complete green-blindness (~1% of men). Both confuse red and green hues. Use the deuteranomaly test page for the partial form.
Is deuteranopia the same as red-green color blindness?
It is the severe green-axis form of red-green CVD. Protanopia is the red-axis counterpart. A screening test can suggest which pattern fits better; a clinic confirms it.
Test yourself or your designs now
Our free test screens for deuteranopia, tritanopia, protanopia, and achromatopsia in under 2 minutes.