astigmatism vs astigmatic

astigmatism is a noun but astigmatic is not a noun.

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

astigmatism (noun)	astigmatic (noun)
(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

astigmatism (adjective)	astigmatic (adjective)
	of or relating to a defect in the eye or in a lens caused by a deviation from spherical curvature which prevents light rays from meeting at a common focus and so results in distorted images