aniseikonia vs vision defect

aniseikonia and vision defect both are nouns.

Word	Noun	Adjective	Verb	Adverb
aniseikonia	Yes	No	No	No
vision defect	Yes	No	No	No

As nouns, vision defect is a hypernym of aniseikonia; that is, vision defect is a word with a broader meaning than aniseikonia:

aniseikonia: visual defect in which the shape and size of an ocular image differ in the two eyes
vision defect: impairment of the sense of sight

Other hypernyms of aniseikonia include visual defect, visual disorder, visual impairment.

aniseikonia (noun)	vision defect (noun)
visual defect in which the shape and size of an ocular image differ in the two eyes	impairment of the sense of sight