Test Methodology, Sources & Limitations

What the test checks

The main test uses 17 number plates. Dots of different colors form digits that may look different, or disappear, for people with red-green color vision deficiencies. The answer pattern produces a screening indication of typical color vision or a possible red-green difference.

Classification plates can suggest a protan (red-type) or deutan (green-type) tendency, but an online result cannot reliably establish the exact type or severity.

Why screen-based testing has limits

• Displays differ in color gamut, brightness, contrast, and calibration.
• Night mode, blue-light reduction, grayscale, and system color filters alter the plates.
• Ambient light, glare, viewing angle, and response time affect recognition.
• Ishihara-style plates mainly screen red-green deficiencies; they do not rule out tritan (blue-yellow) deficiencies or other vision conditions.

When to seek professional testing

Consult an optometrist or ophthalmologist if repeated screens are concerning, a child consistently struggles with color-coded work, color perception has changed recently, or color vision matters for driving or occupational safety. A professional can test under controlled lighting and may use color plates, hue arrangement tests, or an anomaloscope.

Privacy and results

No account is required. On completion, answers, timing, and basic browser and screen information are saved with a random, unlisted result link. Anyone with the link can view the result. Do not treat it as a medical record or certificate.

Primary sources

• U.S. National Eye Institute: Testing for Color Vision Deficiency
• UK Health and Safety Executive: Colour Vision Examination
• Shinobu Ishihara, Tests for Colour-blindness, 38-plate edition.
• Cole BL. Assessment of inherited colour vision defects in clinical practice. Clinical and Experimental Optometry, 2007.