keratectasia vs astigmia

keratectasia and astigmia both are nouns.

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

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

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

Other hypernyms of keratectasia include astigmatism.

keratectasia (noun)	astigmia (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