Source : Webster's Revised Unabridged Dictionary (1913)

Daltonism \Dal"ton*ism\, n.
   Inability to perceive or distinguish certain colors, esp.
   red; color blindness. It has various forms and degrees. So
   called from the chemist Dalton, who had this infirmity.
   --Nichol.

Source : WordNet®

Daltonism
     n : dichromacy characterized by a lowered sensitivity to green
         light resulting in an inability to distinguish green and
         purplish-red [syn: {deuteranopia}, {green-blindness}]