color vision deficiency

NOUN
23 LETTERS · STARTS WITH C

color vision deficiency is a valid 23-letter word worth 37 points in Scrabble and 43 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
C3O1L1O1R1V4I1S1I1O1N1D2E1F4I1C3I1E1N1C3Y4
3 + 1 + 1 + 1 + 1 + 0 + 4 + 1 + 1 + 1 + 1 + 1 + 0 + 2 + 1 + 4 + 1 + 3 + 1 + 1 + 1 + 3 + 4 =37 PTS
DOUBLE WORD → 74TRIPLE WORD → 111
MEANING

What does color vision deficiency mean?