simple eye vs eye

simple eye and eye both are nouns.

Word	Noun	Adjective	Verb	Adverb
simple eye	Yes	No	No	No
eye	Yes	No	Yes	No

As nouns, eye is a hypernym of simple eye; that is, eye is a word with a broader meaning than simple eye:

Other hypernyms of simple eye include oculus, optic.

simple eye (noun)	eye (noun)
an eye having a single lens	a small hole or loop (as in a needle)
	the organ of sight
	good discernment (either visually or as if visually)
	attention to what is seen
	an area that is approximately central within some larger region

simple eye (verb)	eye (verb)
	look at