The Ishihara test is a widely used colour vision test made up of plates filled with coloured dots. Hidden numbers or pathways appear in the dots to people with normal colour vision.
How it works
The pattern reveals red-green deficiencies.
- Each plate is shown briefly at a comfortable reading distance
- The person names the number or traces the line they can see
- Those with red-green colour blindness may see different figures or none at all
- Scores across several plates indicate whether colour vision is normal or defective
Uses and limits
The Ishihara test is a screening rather than a full diagnostic tool.
- Primarily detects inherited red-green defects, not all colour problems
- Lighting and familiarity with numbers can influence results
- Abnormal findings can be followed by more detailed colour vision testing
- Often used in school, occupational, and pre‑employment assessments
