Protanomaly Test (Red-Weak)
This Ishihara-style test screens for protanomaly, a mild form of red-green color blindness where the red-sensitive (L) cones are present but spectrally shifted. People with protanomaly may have difficulty with some or all of these plates depending on the severity of their condition.
Plate 1 of 10
What number do you see in the circle above?
Test Instructions
- Look at each colored circle
- Enter the number you see (if any)
- Take your time — there's no rush
- Make sure your screen brightness is normal
- Ensure good lighting conditions
Medical Disclaimer: This online test is a screening tool. While it can help identify potential color vision deficiencies, it is not a substitute for professional medical diagnosis. Screen brightness, lighting conditions, and display calibration can affect results.
What This Test Screens For
Protanomaly is a form of anomalous trichromacy where L-cones are present but have their peak sensitivity shifted toward shorter wavelengths, overlapping more with M-cones. This reduces red-green color discrimination. Unlike protanopia (complete L-cone absence), protanomaly varies in severity, from barely detectable to nearly as impaired as protanopia.
Limitations of This Test
Ishihara-style plates cannot distinguish protanomaly from protanopia, deuteranopia, or deuteranomaly. They screen for red-green deficiency as a category. A definitive protanomaly diagnosis requires an anomaloscope, which measures how much extra red light you need to match a yellow reference. People with mild protanomaly may pass this screening despite having measurable color vision differences.
What to Expect
You will see 10 circular plates with hidden numbers. People with protanomaly typically get some plates correct and miss others, depending on severity. This partial performance pattern is what distinguishes anomalous trichromacy from complete dichromacy in clinical testing, though this screening cannot make that distinction alone.
How Protanomaly Differs from Protanopia
In protanopia, the L-cones are entirely absent, resulting in dichromatic vision. In protanomaly, the L-cones are present but tuned to a slightly different wavelength than normal, resulting in anomalous trichromatic vision. People with protanomaly can still perceive some red, but it appears duller and more muted. The severity varies widely: mild cases may barely notice any color confusion, while severe cases approach the level of protanopia.
Color-Filtering Glasses and Protanomaly
Color-filtering glasses tend to be more effective for anomalous trichromats like those with protanomaly than for dichromats. Because the L-cones are still functional (just shifted), the enhanced spectral separation provided by filter lenses can meaningfully improve color discrimination. Many users report that reds and greens appear more vivid and distinct with the glasses on.
Frequently Asked Questions
Can protanomaly get worse over time?
Inherited protanomaly is stable throughout life. However, age-related changes like lens yellowing can independently affect color perception. If you notice a change in your color vision, see an eye care professional to rule out acquired causes.
How common is protanomaly?
Protanomaly affects approximately 1% of men and 0.03% of women. It is less common than deuteranomaly (5% of men) but similar in frequency to protanopia and deuteranopia.
Learn more about this condition
Related Tests
Protanopia Test (Red-Blind)
This Ishihara-style test screens for protanopia, the complete absence of red-sensitive (L) cones. If you have protanopia, you will have difficulty seeing the numbers hidden in these plates because the foreground and background colors fall along the red-green confusion axis.
Deuteranomaly Test (Green-Weak)
This Ishihara-style test screens for deuteranomaly, the most common color vision deficiency worldwide. Deuteranomaly occurs when the green-sensitive (M) cones have a shifted spectral response, reducing the ability to distinguish between reds, greens, and similar hues.
Red-Green Colorblind Test
This Ishihara-style test screens for all types of red-green color blindness, including protanopia, deuteranopia, protanomaly, and deuteranomaly. Red-green color deficiency is the most common form of color blindness, affecting approximately 8% of men and 0.4% of women worldwide.