Colorblind Lab

Types of Color Vision Deficiency

The human eye has three kinds of cone cells that respond differently depending on the wavelength of light: long (L, toward red), medium (M, toward green), and short (S, toward blue). When one of these cone types is missing (color blindness, or dichromacy) or its sensitivity is shifted (color weakness, or anomalous trichromacy), certain colors become hard to tell apart.

The color strip for each type shows the same ten colors simulated through that type's eyes (Machado 2009 model). It may differ from reality depending on your monitor.

10 reference colors as seen with normal color vision

Protanopia (red-blind) Protanopia · protan dichromacy Without the long-wavelength L cones, red, green, brown, and orange are hard to tell apart, and red looks darker than it is. Men ~1.0% Protanomaly (red-weak) Protanomaly · protan anomalous trichromacy The L cones are present, but their sensitivity is shifted toward M, weakening red-green discrimination and making red look dull and dark. Men ~1.1% Deuteranopia (green-blind) Deuteranopia · deutan dichromacy Without the medium-wavelength M cones, red and green are hard to tell apart — but unlike protanopia, red keeps nearly its normal brightness. Men ~1.3% Deuteranomaly (green-weak) Deuteranomaly · deutan anomalous trichromacy The most common type of color vision deficiency. M-cone sensitivity is shifted toward L, weakening discrimination among greens and related colors. Men ~4.6% Tritanopia (blue-yellow blind) Tritanopia · tritan dichromacy Without functioning short-wavelength S cones, blue ↔ green and yellow ↔ pink/purple get confused. Very rare. <1 in 10,000 Tritanomaly (blue-yellow weak) Tritanomaly · tritan anomalous trichromacy Weakened S-cone function blurs the distinction between blue and green, and between yellow and pink. The congenital form is very rare; acquired forms are more common. Very rare Achromatopsia (rod monochromacy) Achromatopsia · Rod monochromacy With almost no working cones, the world is seen only through differences in brightness. Reduced visual acuity, severe glare sensitivity, and nystagmus come with it. ~1 in 30,000 Blue cone monochromacy Blue cone monochromacy · S-cone monochromacy With neither L nor M cones working, vision relies on S cones and rods alone. Color discrimination is nearly absent and visual acuity is reduced. ~1 in 100,000

Three main groups

Names vary by country and field. In English, “color blindness” is the everyday umbrella term — it usually refers to red-green deficiency and covers mild cases too — while clinicians and researchers prefer “color vision deficiency” (CVD), reserving “-anopia” for dichromacy and “-anomaly” for anomalous trichromacy.