astigmatism

UK: /əˈstɪgmətɪzəm/ US: /əˈstɪgməˌtɪzəm/ ,(ə stig′mə tiz′əm)

WordReference Random House Learner's Dictionary of American English © 2026

a•stig•ma•tism /əˈstɪgməˌtɪzəm/   n. 

1. Ophthalmology a failure of the eye to see properly because parallel rays of light from the outside image do not line up and meet at a single point on the retina:
   [uncountable] has astigmatism in one eye.
   [countable; usually singular]
   had a slight astigmatism.

as•tig•mat•ic /ˌæstɪgˈmætɪk/  adj. 

WordReference Random House Unabridged Dictionary of American English © 2026

a•stig•ma•tism  (ə stig′mə tiz′əm), n. 

Also called a•stig•mi•a  (ə stig′mē ə). [Ophthalm.] a refractive error of the eye in which parallel rays of light from an external source do not converge on a single focal point on the retina.
1. Optics an aberration of a lens or other optical system in which the image of a point is spread out along the axis of the system.

• astigmat(ic) + -ism 1840–50

Collins Concise English Dictionary © HarperCollins Publishers::

astigmatism / əˈstɪɡməˌtɪzəm/, astigmia / əˈstɪɡmɪə/ noun

1. a defect of a lens resulting in the formation of distorted images; caused by the curvature of the lens being different in different planes
2. faulty vision resulting from defective curvature of the cornea or lens of the eye