The Collaborative International Dictionary of English v.0.48:

Alexia \A*lex"i*a\ ([.a]*l[e^]ks"[i^]*[.a]), n. [NL.; a- not +
   Gr. le`xis speech, fr. le`gein to speak, confused with L.
   legere to read.] (Med.)
   (a) Inability to read aloud, due to brain disease; the
       meanings of the words is nevertheless understood. Called
       also motor alexia.
   (b) Inability, due to brain disease, to understand written or
       printed symbols. Called also Word blindness and text
       blindness.
       [Webster 1913 Suppl. + AS] Alexipharmac

WordNet (r) 3.0 (2006):

alexia
    n 1: inability to perceive written words [syn: visual aphasia,
         alexia, word blindness]