Color vision deficiency
Reduced or absent ability to distinguish certain colors — most commonly red and green — usually inherited and lifelong.
Open VisualSim →What it looks like
The four main types: Protanopia / protanomaly (reduced red sensitivity) makes reds appear dark and brownish, often confused with green. Deuteranopia / deuteranomaly (reduced green sensitivity) is the most common form, affecting about 6% of males; greens look beige and confusable with reds. Tritanopia / tritanomaly (reduced blue sensitivity) makes blues appear greenish and yellows pink-gray; rare. Achromatopsia: complete absence of color vision — the world looks grayscale — often with severe light sensitivity and reduced visual acuity.
Why it's usually genetic
The genes for red and green cone receptors are on the X chromosome, which is why protanopia and deuteranopia are far more common in males (one X means no backup copy). About 8% of men and 0.5% of women have some form of red-green color vision deficiency.
When to see a doctor
Inherited color vision deficiency is permanent and doesn't need treatment. However, sudden new color desaturation in one or both eyes — especially with dim vision or pain — can indicate optic neuritis (often associated with multiple sclerosis) or optic nerve compression and should be evaluated promptly.
Also known as
Color blindness · Protanopia · Deuteranopia · Tritanopia · Achromatopsia