Color Vision Screening (Ishihara Test)

Ishihara Color Vision Test

Test Plate Set

Plates Correctly Identified

Score:–

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Assess for red-green color blindness.

Why Use

Provides a rapid assessment of color vision and evaluation of red-green color blindness.

When to Use

To screen for red-green color blindness. This test can also provide an initial assessment regarding the type of red-green color blindness (protan or deutan).

Formula

X means that the plate cannot be read. Dashes denote that the reading is indefinite. Plate number Normal patient Red-green color deficiency Total color blindness 1 12 12 12 2 8 3 X 3 5 2 X 4 29 70 X 5 74 21 X 6 7 X X 7 45 X X 8 2 X X 9 16 X X Protan Deutan Strong Mild Strong Mild 10 35 5 (3)5* 3 3(5)* - 11 96 6 (9)6* 9 9(6)* - *The numbers in parentheses indicate they can be read but are comparatively unclear.

Pearls / Pitfalls

This test evaluates for the most common type of color blindness (red-green deficiency) and not other types of color blindness. For purposes of rapid screening, this test uses an abbreviated version of the concise 14 plate test. The complete test consists of 38 Ishihara pseudoisochromatic plates, and a shorter 24 plate version exists as well. This abbreviated version of the 14 plate test excludes the hidden digit plate (original plate 9) and the line tracing plates (original plates 11 and 14). Testing is less accurate in patients who have near visual acuity less than ~20/100 at 30 inches. This test is less reliable in very young children (<5 years of age). Ishihara pseudoisochromatic plates are the most commonly used initial test for color vision testing; however, there are other tests which may be more accurate and sensitive, but more time-consuming (e.g. Farnsworth Panel D-15 and Farnsworth-Munsell 100-hue tests). An alternative pseudoisochromatic plate test is the Hardy-Rand-Ritter (HRR) test.

Management

Patients with color vision deficiency should undergo further evaluation by an ophthalmologist or neuro-ophthalmologist.

Advice

Patients with more than two incorrect plates are considered to have color vision deficiency.