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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.

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.