Protanopia: Red Blindness and Protanomaly Explained

What is protanopia?

Protanopia is a type of red-green color blindness. The name comes from the Greek "protos" (first) – the red cones are counted as the "first" cone type. In protanopia these L cones are missing completely. People see with only two cone types (blue and green) – they are so-called dichromats.

Protanomaly: the milder form

In protanomaly the red cones are present, but their sensitivity is shifted toward green. Depending on how far the curve moves, it is mild, moderate or strong. People with mild protanomaly often do not notice it at all.

How people with protanopia see

Switch between normal vision, protanomaly and protanopia:

• Red looks dark: without red cones, reds contribute little to brightness. Deep red can look almost black.
• Confusions: red, orange, brown and green look like similar yellow-brown shades; purple looks blue; pink can look gray.
• Still clear: blue and yellow, and differences in brightness.

More examples in what do color blind people see?

Causes and inheritance

Protanopia and protanomaly are inherited. The gene for the red cone pigment (OPN1LW) is on the X chromosome, so red weakness is X-linked recessive and affects almost only men. It stays the same for life.

Protanopia test

Plate tests such as the Ishihara test reliably show whether there is a red-green deficiency; some plates also help tell protan from deutan. Our online test gives you exactly that estimate at the end. Whether it is protanomaly or protanopia is determined by an eye doctor, usually with an anomaloscope.

Living with protanopia

• Driving: red brake lights and tail lights look less bright – keep extra distance. Read traffic lights by position.
• Warning colors: red warnings on dark backgrounds are hard to see – pay attention to symbols and text.
• Aids: phone color filters ("protanopia") and color-identifier apps.
• Glasses: in protanomaly, color blind glasses can raise red-green contrast. In full protanopia the effect is usually smaller.