Colorblindness

Color vision deficiency, commonly called colorblindness, is a visual condition in which colors are perceived differently from typical trichromatic vision. It arises from abnormalities in the cone photoreceptors of the retina or in the brain's processing of color information. The most common forms are red–green and blue–yellow deficiencies; complete color blindness (achromatopsia) is rare.

Most inherited color vision problems are congenital and X-linked, which makes men disproportionately affected. Red–green defects are the most common. Blue–yellow defects and other rare forms may be autosomal recessive. Acquired color vision loss can result from aging, retinal diseases, optic nerve conditions, or certain medications.

Diagnosis relies on history and objective tests. The Ishihara plates screen for red–green deficiencies; the anomaloscope provides precise red–green hue matching; and the Farnsworth–Munsell 100 Hue Test assesses discrimination across hues.

Management focuses on adaptation rather than cure. There is no widely available cure for inherited color vision deficiency. Some individuals benefit from color-filtering lenses or contact lenses, though benefits vary. Practical strategies include high-contrast labeling, accessible design, and assistive digital tools to aid color identification.

Epidemiology varies by population. Approximately 8% of men of Northern European descent have red–green deficiency, with about 0.5% of women affected. Color vision deficiency is a sensory variation, not a disease, and most affected individuals lead normal, productive lives with appropriate accommodations.