How the color-blindness plates work
Roughly 1 in 12 men and 1 in 200 women have some form of color-vision deficiency, most commonly red-green. Ishihara-style plates hide a number in a field of colored dots so that it stands out to people with normal color vision but blends in — or reads as a different number — for those with a deficiency. This tool draws each plate live on a canvas, placing hundreds of dots and coloring the ones inside the digit differently from the background, then asks what you see. Getting several plates wrong can indicate a red-green deficiency worth checking professionally.
Color-hue discrimination and peripheral vision
The hue-arrangement test is inspired by the Farnsworth-Munsell method: you order a row of colored tiles into a smooth gradient, and your 'error score' measures how far each tile sits from its correct position. A low error means fine color discrimination — important for design, art and photography. The peripheral test measures a different sense entirely: keeping your gaze fixed on a central cross, you detect brief flashes appearing at random distances toward the edges, which gauges how wide and responsive your functional field of vision is.
Visual acuity you can actually calibrate
Most 'online eye charts' can't give a real 20/20 figure because they don't know how big your screen is or how far away you sit. This suite fixes that: you hold any bank card, ID or licence to the display and drag a slider until the on-screen box matches its standard 85.6mm width, which tells the test the exact pixel-per-millimetre density of your monitor. You then set your viewing distance, and the Landolt-C rings are drawn at the precise size that corresponds to each Snellen line (20/200 down to 20/20) at that distance. Tap the direction of each shrinking gap; the smallest line you get right becomes your estimated acuity, tested one eye at a time.
Astigmatism, the Amsler grid and contrast sensitivity
The astigmatism fan is a ring of evenly spaced lines — if some directions look darker or blurrier than others, light is focusing unevenly across your eye, the signature of astigmatism. The Amsler grid checks your central (macular) vision: fixate the red dot and watch for lines that appear wavy, blurred, dark or missing, which can be an early warning of macular conditions such as AMD and is worth acting on promptly. The contrast-sensitivity test shows three-digit numbers that fade toward the grey background across ten levels; the faintest you can read reflects your low-contrast vision, which plain acuity charts miss and which matters for night driving and low light.
A screener, not a diagnosis
Screen brightness, color calibration, size, ambient light and viewing distance all affect these tests, so treat the results as a helpful indication rather than a clinical verdict. Uncalibrated monitors can shift colors enough to change plate results, and screen-based acuity is an estimate, not a lane-1 chart in a controlled room. If any test suggests a problem — or if you have any concern about your vision, especially distortion on the Amsler grid — see a qualified optometrist or ophthalmologist, who can perform properly calibrated, standardized examinations.
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- Color-blindness screener with 8 Ishihara-style dot plates generated live on a canvas.
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- Color-hue arrangement test (Farnsworth-style) that scores how accurately you order hues.
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- Screen-calibrated visual acuity test: match a bank card to size your display, then read Landolt-C rings for a 20/20-style Snellen estimate.
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- Astigmatism fan chart that reveals whether some line directions look darker or blurrier.
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- Amsler grid for central/macular vision, with per-eye testing for wavy or missing areas.
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- Contrast-sensitivity test using digits that fade toward the background across 10 levels.
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- Peripheral-vision test that flashes targets at random eccentricities while you fixate the centre.
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- Clear per-test feedback and metrics computed from your own answers, with prominent 'not a diagnosis' guidance.
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- Runs entirely in your browser — no camera, no photos, no uploads, no signup.
