The original meaning of the root (in Proto-Indo-European) is pretty clearly 'eye' or 'see', but in Greek it usually means 'face'. From what I know of *Eryops*, the 'face' meaning would certainly seem to make more sense.
My understanding was that it refers to the portion of the face including the eyes and the nose, but not the mouth. (Different languages sometimes parse the human body slightly differently.)
CMIIW, -- Mike Keesey The Dinosauricon: http://dino.lm.com Parry & Carney: http://parryandcarney.com