keratectasia vs astigmatism

keratectasia and astigmatism both are nouns.

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

As nouns, astigmatism is a hypernym of keratectasia; that is, astigmatism is a word with a broader meaning than keratectasia:

keratectasia: abnormal bulging of the cornea of the eye
astigmatism: (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people

Other hypernyms of keratectasia include astigmia.

keratectasia (noun)	astigmatism (noun)
abnormal bulging of the cornea of the eye	(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