How to remember protoanopia, deuteranopia, and tritanopia

Dichromatism is a form of color blindness in which one of the three cone receptor subtypes is missing or abnormal. There are three possible forms, which are protoanopia, deuteranopia, and tritanopia.

It has been difficult for me to remember which name represents which form of dichromatism even though I have taught this topic for a long time. The names really didn't make much sense.

Today, this mental block was resolved. Here's a way to remember these forms and their underlying issues.

• Protoanopia: Proto means one or first, a synonym for primitive. These individuals are missing the long wavelengths, the L or "red" cones.
• Deuteranopia: Deuter referring to second, like the word deuce. This refers to the medium wavelengths, the M or "green" cones.
• Triatanopia: The Tri prefix means third. This represents the short wavelengths, S or "blue". 

This scheme is ordered 1, 2, and 3 for the long, medium, and short wavelengths, respectively. Problem solved!