Tritanopia Test (Blue-Yellow Blind)
This test uses blue-yellow pseudoisochromatic plates specifically designed to screen for tritanopia and tritan-type color vision deficiency. Unlike standard Ishihara tests, which only detect red-green deficiency, these plates use colors along the tritan confusion axis.
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
Tritanopia is a rare form of color blindness caused by the absence of S-cones (short-wavelength, blue-sensitive). This test uses plates where the foreground number is rendered in blue-violet tones against a yellow-gold background at matched luminance. A person with normal S-cone function easily distinguishes these hues. A person with tritanopia cannot resolve the blue-yellow difference.
Limitations of This Test
This screening uses digitally generated pseudoisochromatic plates, not clinically validated HRR or Farnsworth D-15 panels. While the plates are designed along the tritan confusion axis with luminance matching, monitor color accuracy significantly affects results. A clinical evaluation with standardized instruments is recommended for definitive diagnosis. This test cannot distinguish tritanopia from tritanomaly.
What to Expect
You will see 10 circular plates with colored dots in blue-purple and yellow-gold tones. Each plate hides a number visible to people with normal blue-yellow discrimination. Enter the number you see or indicate you see nothing. The test takes 2-3 minutes.
Why Standard Colorblind Tests Miss Tritanopia
The Ishihara color plate test, used in most screening programs worldwide, is designed exclusively for red-green color vision deficiency. Its plates use colors along the protan/deutan confusion axis. People with tritanopia will pass an Ishihara test with a normal score because their red and green discrimination is intact. Detecting tritan-type deficiency requires plates that use colors along the blue-yellow confusion axis, which is exactly what this test provides.
How This Tritan Test Works
Each plate presents a number rendered in blue-violet tones against a background of yellow-gold tones. The key design principle is luminance matching: the foreground and background have approximately equal brightness, so the number can only be distinguished through hue discrimination. A person with functioning S-cones perceives the blue-yellow hue difference clearly. A person with absent or reduced S-cone function sees both regions as similar, making the number invisible.
Understanding Tritanopia
Tritanopia affects approximately 0.003% of the population and, unlike red-green deficiency, occurs at equal rates in men and women because the responsible gene (OPN1SW) is on chromosome 7 rather than the X chromosome. People with tritanopia confuse blues with greens and yellows with light grays or pinks. The condition can be inherited or acquired through age-related lens yellowing, glaucoma, or macular disease.
Frequently Asked Questions
Why can't a regular Ishihara test detect tritanopia?
Ishihara plates use colors along the red-green confusion axis, which is the wrong axis for detecting tritan deficiency. People with tritanopia have normal red-green discrimination and will pass an Ishihara test. Detecting tritanopia requires plates that use blue-yellow confusion colors, which is what this test provides.
Is tritanopia always inherited?
No. Inherited tritanopia is very rare. Acquired tritan-type deficiency is more common in clinical practice and can develop from aging (lens yellowing), cataracts, glaucoma, macular degeneration, or certain medications. If you notice a new difficulty distinguishing blues from greens, consult an eye care professional.
How is tritanopia different from red-green colorblindness?
Red-green colorblindness (protanopia, deuteranopia, protanomaly, deuteranomaly) involves the L-cones or M-cones and causes confusion between reds and greens. Tritanopia involves the S-cones and causes confusion between blues and yellows. The two types affect different parts of the color spectrum and are detected by different tests.
Does tritanopia affect both men and women equally?
Yes. Unlike red-green color blindness, which is X-linked and primarily affects males, tritanopia is linked to a gene on chromosome 7 (an autosome). This means men and women are affected at the same rate, approximately 0.003% of the population.
Learn more about this condition
Related Tests
Tritanomaly Test (Blue-Weak)
This test uses blue-yellow pseudoisochromatic plates to screen for tritanomaly, an extremely rare condition where the blue-sensitive (S) cones have altered spectral sensitivity. Standard Ishihara tests cannot detect tritan-type deficiency.
Blue-Yellow Colorblind Test
This test uses specialized blue-yellow pseudoisochromatic plates to screen for tritan-type color vision deficiency, including tritanopia and tritanomaly. Standard Ishihara tests cannot detect these conditions because they only test the red-green axis.
Achromatopsia Test (Complete Color Blindness)
This comprehensive test combines both red-green (Ishihara-style) and blue-yellow (tritan-style) plates to screen for achromatopsia, a rare condition in which all cone photoreceptors are nonfunctional. A person with achromatopsia will have difficulty with both plate types.