visual impairment vs vision defect

visual impairment and vision defect both are nouns.

Word	Noun	Adjective	Verb	Adverb
visual impairment	Yes	No	No	No
vision defect	Yes	No	No	No

As nouns, visual impairment and vision defect are synonyms defined as:

Other synonyms of visual impairment include visual defect, visual disorder.

visual impairment (noun)	vision defect (noun)
impairment of the sense of sight	impairment of the sense of sight