Ishihara Color-Blind Test Online

This Ishihara color vision screening with adaptive difficulty uses procedurally generated dot plates to probe red-green perception on both protan (L-cone) and deutan (M-cone) axes. It’s built for quick, repeatable screening: students, clinicians-in-training, pilots-in-training, designers, and anyone curious about color discrimination can complete 20 plates and receive structured results (score, accuracy, per-axis thresholds, response times, and a concise interpretation). The engine escalates difficulty as you answer correctly and estimates color discrimination thresholds rather than giving a simple pass/fail-useful as a pre-check before formal testing with standardized material.

Ishihara Multi‑Axis Color Vision Screening

This adaptive screening simulates Ishihara-style plates across red–green axes (Protan & Deutan) to estimate colour discrimination thresholds.

Test Instructions

Look at the circle and identify the number formed by the coloured dots
Type the number you see in the input field and click Submit
If you cannot see a number, you can click Skip
The test adapts per colour axis; harder plates appear after consistent correct responses
Complete all 20 plates for a comprehensive assessment
Ensure neutral lighting; disable colour boosting / night mode / HDR
The test measures your response time for each plate

Difficulty: Medium

Plate 1 of 20 0 Correct

Test Results

Score: 0/20

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How to use the test

Check your setup: disable Night Shift/blue-light filters/HDR, use neutral room lighting, and view at arm’s length on a well-calibrated display.
Start the session and look for the number formed by colored dots inside the circle.
Enter the number (1-99) and select Submit, or choose Skip if no number is visible.
The screening adapts to performance: several correct responses increase challenge; errors reduce it.
Watch the difficulty indicator; it shows both level and which axis (Protan or Deutan) you’re on.
At the end you’ll see score, accuracy, median response time, and estimated per-axis threshold (smallest Δh resolved).
Interpreting results: lower thresholds (smaller Δh) with good accuracy suggest typical red-green discrimination; consistently high thresholds or difficulty at easier levels may indicate a protan or deutan deficiency pattern and merit clinical testing.

Features and what the results mean

Adaptive Ishihara-style plates across two axes: Protan (L-cone) and Deutan (M-cone)
Seven difficulty levels (Very Easy → Extreme) that tune hue separation (Δh), saturation, dot density, and numeral size
Smart scheduling that alternates axes based on your recent performance to gather balanced evidence fast
Extreme threshold probing at the top level with micro-steps to pinpoint the smallest resolvable Δh
Lightness-matched figure/background dots to minimize luminance cues and stress true chromatic discrimination
Procedurally generated dot patterns and distractor shapes for high plate variety and low memorization effects
Real-time difficulty indicator showing level and current axis (Protan or Deutan)
Instant feedback (Correct/Incorrect/Skipped) with per-plate response time readout
Comprehensive session metrics: score (n/20), accuracy (%), median response time (ms)
Per-axis threshold estimate: smallest Δh (degrees) you resolved for Protan and Deutan
Automatic per-axis classification (normal / mild / moderate / marked / severe) derived from your thresholds
Detailed performance breakdown by level and axis, including attempts, correct count, and accuracy
Quality checks that flag too-few trials, unusually fast/slow responses, or unbalanced axis sampling
Clear result headline summarizing whether findings align with typical red-green perception or a protan/deutan pattern

Ishihara plate with number 28 on it

Practical background: red-green screening-what matters

Protan vs deutan patterns: Protan deficiency shifts sensitivity linked to L-cones (often affecting reds); deutan deficiency involves M-cones (affecting greenish hues).

Why thresholds beat pass/fail: A numeric threshold (Δh) reveals how close two colors can be before they fuse-useful for monitoring change over time.

Real-world impact: Elevated thresholds can affect tasks relying on red-green cues (status LEDs, wiring, safety signals, aviation PAPI lights, medical imaging overlays, UI states).

Display considerations: Gamut, brightness, viewing angle, and color-management settings can bias results; repeatability improves with consistent setup.

When to seek clinical testing: Persistent difficulty at moderate levels, asymmetric results (only protan or only deutan affected), or functional problems at work/school.

FAQ

What does this Ishihara-style screening measure? It estimates red-green color discrimination thresholds and patterns along protan and deutan axes using adaptive plates.
Is this the same as the official Ishihara test? No. It emulates Ishihara principles for screening; official, standardized plates are used for clinical diagnosis.
What is a “threshold Δh”? It’s the smallest hue separation (in degrees) you correctly identified; lower numbers indicate finer discrimination.
What’s the difference between protan and deutan deficiency? Protan involves L-cones (red component), deutan involves M-cones (green component); each can elevate thresholds differently.
Why might my results vary day to day? Lighting, display settings, fatigue, and attention can change performance; keep conditions consistent.
Can I “train” my score? Familiarity reduces uncertainty, but true congenital red-green deficiencies won’t be corrected by practice.
What should I do if my thresholds are high? Repeat under neutral conditions and consider a formal color vision assessment with standardized tests.