eye movement vs saccade

eye movement and saccade both are nouns.

Word	Noun	Adjective	Verb	Adverb
eye movement	Yes	No	No	No
saccade	Yes	No	No	No

As nouns, saccade is a hyponym of eye movement; that is, saccade is a word with a more specific, narrower meaning than eye movement:

Other hyponyms of eye movement include nystagmus.

eye movement (noun)	saccade (noun)
the movement of the eyes	a rapid, jerky movement of the eyes between positions of rest
	an abrupt spasmodic movement