color blindness

Table 1 Examples of colours that might be confused by colour deficient observers Colour deficiency Examples of colours that might be confused Protanope Blue--green/white/red Pale blue/purple/magenta Red/orange/yellow/green Deuteranope Purple/Grey/greenish blue-green Red/orange/yellow/green Red/brown, green/brown Tritanope Yellow/white Violet/yellow-green Red/red-purple

Phenotypical variations are characteristic of autosomal inheritance and some family members are tritanopes while others are incomplete tritanopes that express some S photopigment.

Dichromats lack red pigment gene and those lacking green pigment gene are known as Protanopes while those lacking blue green pigment are known as Tritanopes (4).

(1) Mean position of the center cap Range Protanopes 17 15-26 64 58-68 Deuteranopes 15 12-17 58 53-60 Tritanopes 5 4-6 45.5 45-46

The neutral points for deuteranopes, protanopes and tritanopes are around 498nm, 492nm and 569nm respectively.