Ishihara Test Answers and Scoring

Answer key for our 20 plates

Take the test first: reading the answers before you start makes the result meaningless. The table is generated from the same data the test uses, so it always matches the plates.

Answers for each plate; "nothing" means the number is expected to disappear.

Plate	Typical vision	Red-weak (protan)	Green-weak (deutan)	Blue-yellow (tritan)	Tests	Fades at
1	12	12	12	12	Control (everyone)	—
2	8	nothing	8	8	Red-green screening	84%
3	29	29	nothing	29	Red-green screening	83%
4	5	nothing	nothing	5	Red-green screening	83%
5	74	nothing	74	74	Red-green screening	76%
6	26	6	2	26	Protan / deutan	83%
7	3	3	nothing	3	Red-green screening	71%
8	45	nothing	nothing	45	Red-green screening	66%
9	6	6	6	6	Blue-yellow	—
10	97	nothing	nothing	97	Red-green screening	64%
11	42	2	4	42	Protan / deutan	71%
12	16	nothing	nothing	16	Red-green screening	58%
13	73	73	73	73	Control (everyone)	—
14	58	58	58	nothing	Blue-yellow	91%
15	2	nothing	nothing	2	Red-green screening	53%
16	35	nothing	nothing	35	Protan / deutan	58%
17	61	nothing	nothing	61	Red-green screening	49%
18	9	9	9	nothing	Blue-yellow	75%
19	84	nothing	nothing	84	Red-green screening	46%
20	47	47	47	nothing	Blue-yellow	53%

How to read the answer table

• Typical vision: the number most people read.
• Red-weak and green-weak: what someone with a strong protan or deutan deficiency (dichromacy) is expected to read.
• Fades at: the simulated severity at which the figure becomes too faint to see. A plate that fades at 50% is missed even by people with a moderate deficiency.
• Two-digit classification plates show one digit to red-weak vision and the other to green-weak vision. That is how the test tells protan from deutan.

How the Ishihara test is scored

The printed Ishihara test uses a simple count of correctly read plates. These are the thresholds given in the instructions that come with the test.

What your score means

• Normal: you read nearly all plates. One or two misses on faint plates is common.
• Borderline: a score between the two thresholds (14 to 16 of 21 in the full edition) is rare and needs a retest or another test.
• Red-green deficiency: you missed many plates. Classification plates then suggest protan or deutan; a clinic can confirm the type and severity.

How Ishihara results are written down

Clinicians usually record the edition and the score, for example "Ishihara 38: 21/21" or "Ishihara 24: 8/15, deutan". The plates read the colour-deficient way are often listed too, and whether both eyes or each eye was tested.

What to do after a failed screening

Book an eye examination. An optometrist can confirm the type, measure severity with tests such as the Farnsworth D-15 or an anomaloscope, and check for any eye condition if the loss is new or affects one eye.