ptosis vs brow ptosis

ptosis and brow ptosis both are nouns.

Word	Noun	Adjective	Verb	Adverb
ptosis	Yes	No	No	No
brow ptosis	Yes	No	No	No

As nouns, brow ptosis is a hyponym of ptosis; that is, brow ptosis is a word with a more specific, narrower meaning than ptosis:

ptosis: drooping of the upper eyelid caused by muscle paralysis and weakness
brow ptosis: sagging eyebrows

ptosis (noun)	brow ptosis (noun)
drooping of the upper eyelid caused by muscle paralysis and weakness	sagging eyebrows