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Also called astigmia
[uh-stig-mee-uh] /əˈstɪg mi ə/ (Show IPA). Ophthalmology. 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.
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.
Historical Examples

I have astigmatism in one eye, and have therefore to wear special spectacles.
The Girls of St. Wode’s L. T. Meade

A diagram similar to Fig. 394 is used as a test for astigmatism.
Physics Willis Eugene Tower

To such let me explain that I am suffering from astigmatism.
Humorous Ghost Stories Dorothy Scarborough

There is one other defect of vision that is so common as to call for a word; this is astigmatism.
Physiology Ernest G. Martin

There seems to be a sort of astigmatism that keeps us from seeing things straight.
Quiet Talks on Service S. D. Gordon

One of the most common forms of defective vision is astigmatism.
Initiative Psychic Energy Warren Hilton

When this form of astigmatism is excessive, it may be corrected by the use of spectacles fitted with cylindrical lenses.
Curiosities of Light and Sight Shelford Bidwell

That’s no reason for calling in the neighbors to rejoice with him because he has astigmatism.
The Vision Spendid William MacLeod Raine

astigmatism produced by the incision is corrected with glasses.
A System of Operative Surgery, Volume IV (of 4) Various

In Manitou when men get drunk, the people get astigmatism and can’t see the tangledfooted stagger.
The World For Sale, Complete Gilbert Parker

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

1849, coined by the Rev. William Whewell (1794-1866), English polymath, from Greek a- “without” (see a- (3)) + stigmatos genitive of stigma “a mark, spot, puncture” (see stick (v.)).

astigmatism a·stig·ma·tism (ə-stĭg’mə-tĭz’əm)
n.
A condition in which unequal curvatures along the different meridians in one or more of the refractive surfaces of the eye cause the rays from a light source not to be focused at a single point on the retina. Also called astigmia.
as’tig·mat’ic (ās’tĭg-māt’ĭk) adj. & n.
astigmatism
(ə-stĭg’mə-tĭz’əm)

A visual defect in which the unequal curvature of one or more refractive surfaces of the eye, usually the cornea, prevents light rays from focusing clearly at a single point on the retina, resulting in blurred vision.
astigmatism [(uh-stig-muh-tiz-uhm)]

A condition in which the curvature of the cornea of the eye is uneven, causing a blurring of vision. Astigmatism is normally corrected by glasses.