Start the test
Menu

Home › Types of color blindness › Protanomaly

Protanomaly

In protanomaly the red-sensitive (L) cones are shifted towards the green-sensitive cones. Reds look darker and less saturated, and red-green distinctions become harder. Severity ranges from mild to strong.

Protanomaly is the milder form of protan color blindness, often called red-weak color vision. The complete form is protanopia.

Red-green color vision deficiency · Last updated 2026-11-10

What does protanomaly look like?

Illustration of fruit in a blue bowl with typical color vision: red apple, green apple, yellow lemon, orange, purple grapes, pink peach and blueberries.Typical color vision
The same fruit bowl simulated with moderate protanomaly. Reds turn darker and browner, orange moves toward yellow, and green loses some of its contrast with red. Blue and yellow stay clear.Simulated moderate protanomaly
Reds turn darker and browner, orange moves toward yellow, and green loses some of its contrast with red. Blue and yellow stay clear.
Nine color swatches (red, orange, yellow, green, teal, blue, purple, pink and brown) with typical vision and simulated with moderate protanomaly.
Common colors with typical vision (top) and simulated moderate protanomaly (bottom). Images are simulations based on the Machado, Oliveira & Fernandes (2009) model at moderate severity; real experience varies from person to person and with your screen.
  • Reds look darker, duller or more brownish than they do to most people.
  • Red and green, and orange and yellow, can be confused.
  • Deep red text on a dark background can be hard to read.

Try our color blind simulator to see your own photos the way someone with a protan deficiency might.

How common is protanomaly?

About 1% of men; rare in women.

Everyday situations that can be tricky

  • Red warning lights and red laser pointers can be harder to spot.
  • Red/green indicators on devices and charts.
  • Distinguishing some purples from blues.

Causes

Inherited on the X chromosome (OPN1LW/OPN1MW genes). Present from birth and stable.

Protanomaly vs deuteranomaly

Both are anomalous (milder) red-green types. In protanomaly the red-sensitive cones are shifted, so reds also look darker; in deuteranomaly the green-sensitive cones are shifted and reds keep their brightness. Deuteranomaly is much more common, at about 5% of men compared with about 1% for protanomaly.

Read more about deuteranomaly.

Glasses, apps and other aids

Some people with protanomaly report better red-green contrast with color-enhancing glasses, though results tend to be weaker than for deuteranomaly. What the studies found, type by type: do color blind glasses work?

Phone and computer accessibility settings (color filters), color-identifier apps, and asking for labels or patterns on color-coded information can all help. There is currently no approved cure for inherited color blindness.

How is protanomaly diagnosed?

Eye care professionals use plate tests (such as Ishihara or HRR plates), arrangement tests and, for a precise diagnosis, an anomaloscope. Online tests like ours can flag a likely deficiency but can’t replace a clinical test.

Take the red-green test

Protanomaly FAQ

What is protanomaly?

Protanomaly is an inherited red-green color vision deficiency in which the red-sensitive (L) cones work but are shifted toward the green-sensitive cones. Red-green differences shrink and reds look darker.

What does protanomaly look like?

Reds look darker and duller, and some reds, oranges, yellows and greens are harder to tell apart. The images above simulate a moderate case; mild protanomaly can be barely noticeable.

Is protanomaly the same as protanopia?

No. In protanomaly the red-sensitive cones are present but shifted, so some red-green discrimination remains. In protanopia they are missing or not working. Both are protan color blindness.

What is mild protan color blindness?

It usually means mild protanomaly: a small shift in the red-sensitive cones that may only show up on tests or with dark and muted colors. Our test estimates severity, but only an eye care professional can confirm it.

Can protanomaly be cured?

There is currently no approved cure for inherited protanomaly. It is present from birth and normally stays the same throughout life.

Other types of color blindness

Protanomaly is one of four types of red-green color blindness. See all types of color blindness compared side by side, or what colorblind people see with each type.

Sources

  1. National Eye Institute. Types of color vision deficiency. nei.nih.gov
  2. MedlinePlus Genetics, U.S. National Library of Medicine. Color vision deficiency. medlineplus.gov
  3. Birch J. Worldwide prevalence of red-green color deficiency. JOSA A. 2012;29(3):313–320. doi.org
  4. Nathans J, Piantanida TP, Eddy RL, Shows TB, Hogness DS. Molecular genetics of inherited variation in human color vision. Science. 1986;232(4747):203–210. pubmed.ncbi.nlm.nih.gov
  5. Simunovic MP. Colour vision deficiency. Eye. 2010;24(5):747–755. pubmed.ncbi.nlm.nih.gov
  6. Machado GM, Oliveira MM, Fernandes LAF. A physiologically-based model for simulation of color vision deficiency. IEEE TVCG. 2009;15(6):1291–1298. (Used for the simulated images.) doi.org

Note: this is a screening, not a diagnosis. Online tests can’t control your screen’s colors or brightness, so confirm any result with an eye care professional. Medical disclaimer · How the test works

Could color-enhancing glasses help?

Glasses with special notch filters can boost the contrast between reds and greens for some people with mild to moderate red-green color vision deficiency (protanomaly or deuteranomaly). They don’t cure color blindness and they work less well for strong types, so look for a trial period or return policy.

Do color blind glasses work?

More color vision tests

Color blind testFull screening: red-green and blue-yellow, with type and severity.Red-green color blind testDeeper check for protan and deutan types.Tritanopia testBlue-yellow (tritan) color vision screening.Color blind test for kidsShapes instead of numbers, for children who can’t read digits yet.Reverse color blind testHidden-figure plates that color blind people can see more easily.Color blind simulatorSee any photo the way people with color blindness see it.