About & Methodology

How the test works

Our plates are original, Ishihara-style pseudoisochromatic plates generated in code. Each plate is a field of coloured dots; the dots forming the hidden figure are drawn from one palette and the background from another. For the diagnostic plates the two palettes share the same brightness band and differ only in hue along a colour axis (red-green or blue-yellow), so the figure separates by colour alone. That's the same principle behind the paper plates used in clinics.

We generate our own plates rather than reproduce published Ishihara plates, which are copyrighted. The test is scored on your device using transparent, documented rules: we tally errors by colour axis, then estimate the most likely type and strength. Control plates that nearly everyone can read help flag a display problem or a rare total deficiency.

Why online results are only a screen

No website can calibrate your screen or your lighting, and monitors vary widely in how they render colour. That's why every result here carries the same message: this is a screen, not a diagnosis. It's a genuinely useful first check, and a prompt to see an eye-care professional when the answer matters. See our medical disclaimer.

Accessibility, by design

Because this is a colour-vision product, the interface itself never relies on colour alone. Results use shapes, labels and a blue-only severity scale, never red/green, so a colour-blind visitor can use the site comfortably. We aim for WCAG 2.2 AA, full keyboard operation and screen-reader support.

Sources

Our explanations draw on established, publicly available sources on colour vision, including the work of Shinobu Ishihara and Dean Farnsworth, and guidance from professional and public-health bodies such as the American Optometric Association (AOA) and the US National Eye Institute (NEI). Where figures vary between studies, we describe them as approximate.

Editorial & medical-review standards

Content is written by our editorial team and dated with a "last reviewed" date. We are committed to having health-related pages reviewed by a licensed optometrist or ophthalmologist; where a named reviewer has completed that review, their name appears in the byline. Until a specific page has been reviewed by a named clinician, we do not claim that it has, we would rather show no reviewer than a fabricated one.

How this is funded

Right now this is simply a free tool, there are no ads and no affiliate links. If we ever add either, we'll label it clearly, and it won't change our honest assessments, including where our answer is "this probably won't help you."

Originality & trademarks

Every test plate on this site is generated by our own software: original dot patterns and colour palettes created from scratch. We do not copy, trace or reproduce the copyrighted plates from any published Ishihara edition or any other test. Our plates are "Ishihara-style" because they use the same well-established pseudoisochromatic principle: a method, not a copyrightable image, not because they are copies of anyone's artwork.

Names such as "Ishihara", "Farnsworth", "D-15" and "anomaloscope" are used here purely descriptively, to identify the established methods we screen with or explain. Our colour-arrangement tool is based on the D-15 method and uses generic on-screen colours, not the official calibrated Munsell caps. Brand names of colour-blind glasses (EnChroma, Pilestone, ColorLite and others) are used only to review and compare those products. We are not affiliated with, sponsored by, or endorsed by any test publisher, instrument maker or eyewear brand, and all trademarks are the property of their respective owners.