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Detect Color Blindness
Red-Green Dichromacy (strong)

Protanopia

By The Detect Color Blindness editorial team Last reviewed

Absent red cones; a strong red-green deficiency.

What Protanopia means

In protanopia the red-sensitive (L) cones are absent. Red light looks very dark, and reds, oranges, yellows and greens are hard to separate. Because reds appear dim, brightness cues can be misleading as well as hue.

What it can look like day to day

  • Red objects can look black or very dark
  • Reds and greens are frequently confused
  • Traffic signals rely on position, not colour
  • Judging ripeness or rare/well-done meat is hard

How common is it?

~1% of men. Colour vision deficiency overall affects roughly 1 in 12 men and 1 in 200 women, see the full prevalence breakdown.

Can glasses help?

For protanopia, colour-correction glasses have mixed results, a strong dichromatic deficiency is harder to help than a mild one, so try before you buy. They don't add missing cones or "cure" anything. Read the honest glasses comparison.

How to test for Protanopia

Start with the free online color blind test or the focused red-green test. For a diagnosis, an eye-care professional uses calibrated plates, an anomaloscope or an arrangement test. Want to see the difference? Try the colour blindness simulator.

Take the color blind test See it in the simulator

Other types of colour blindness

Deuteranomaly Reduced sensitivity to green light, the most common form. Read more → Deuteranopia Absent green cones, a stronger red-green deficiency. Read more → Protanomaly Reduced sensitivity to red light; reds look dimmer. Read more → Tritanomaly Reduced sensitivity to blue light; rare. Read more → Tritanopia Absent blue cones; blue-yellow confusion. Rare. Read more → Achromatopsia (Monochromacy) Little or no colour vision, seeing mostly in shades. Read more →

Frequently asked questions

Is this result a diagnosis?
No. It's an educational screening result based on an online plate test, which can be affected by your screen and lighting. Only an eye-care professional can diagnose colour vision deficiency.
Can color blindness get worse over time?
Inherited colour blindness is stable and does not progress. If your colour vision changes noticeably over time, that can signal an eye or health condition and should be checked by a professional.
Can color blindness be cured?
Inherited colour blindness can't currently be cured. Special filter glasses help some people with red-green types by boosting contrast, and everyday tools and habits make colour tasks easier.

Keep exploring

What next?

Take the color blind test 14 quick plates · instant type & severity · no sign-up. Start the test → See how you see colour Simulate protan, deutan, tritan & more on any image. Open the simulator → Do colour blind glasses work? Honest comparison of EnChroma, Pilestone & ColorLite. Read the guide →