Protanomaly
(Red-Weak Color Vision)
Protanomaly is partial red-axis weakness—less severe than protanopia (complete red-blindness). Free 18-plate screening in under 2 minutes.
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 Protanomaly?
Protanomaly is a form of red-green color vision deficiency where long-wavelength (L) cones are present but do not function normally. The red channel is weakened rather than absent, so colors shift along the red-green axis but some discrimination remains.
Protanomaly vs Protanopia
Protanopia vs protanomaly: protanopes lack functional red cones entirely—reds appear very dark or black. Protanomalous vision retains a shifted red channel, so severity varies from mild confusion to moderate difficulty with red-green tasks. Our protanomaly test uses the same Ishihara screening as a full color blind test.
Everyday Challenges
- Difficulty distinguishing ripe vs unripe fruit
- Red and green traffic lights may look similar in some lighting
- Red error states in UI may be less noticeable than for protanopes
Design & Simulation
Preview UI under partial red weakness with our color blind simulator (severity slider) or compare all CVD types on the color blindness simulation page.
FAQ
What is protanomaly?
Protanomaly is partial red-axis color weakness where L-cones exist but function abnormally. Reds and greens are shifted but not fully absent as in protanopia.
How common is protanomaly?
Protanomaly affects roughly 1% of men. Combined with protanopia, red-axis CVD affects about 2% of all men.
Protanomaly vs protanopia — what's the difference?
Protanopia is complete red-blindness (no working L-cones). Protanomaly is partial weakness—colors along the red-green axis are confused but some red channel remains.