ophthalmology vs astigmatism

ophthalmology and astigmatism both are nouns.

Word	Noun	Adjective	Verb	Adverb
ophthalmology	Yes	No	No	No
astigmatism	Yes	No	No	No

ophthalmology (noun)	astigmatism (noun)
the branch of medicine concerned with the eye and its diseases	(optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point
	(ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people