simple eye vs ocellus

simple eye and ocellus both are nouns.

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

As nouns, simple eye and ocellus are synonyms defined as:

Other synonyms of simple eye include stemma.

simple eye (noun)	ocellus (noun)
an eye having a single lens	an eyelike marking (as on the wings of some butterflies); usually a spot of color inside a ring of another color
	an eye having a single lens