astigmatism

American  

[uh-stig-muh-tiz-uhm] / əˈstɪg məˌtɪz əm /

noun

1. Also called astigmia.  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.

2. 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.

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astigmatism British  

/ əˈstɪɡmɪə, əˈstɪɡməˌtɪzəm /

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

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astigmatism Scientific  

/ ə-stĭg′mə-tĭz′əm /

1. 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.

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astigmatism Cultural  

1. 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.

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Etymology

Origin of astigmatism

First recorded in 1840–50; astigmat(ic) + -ism

Compare meaning

How does astigmatism compare to similar and commonly confused words? Explore the most common comparisons:

• astigmatism vs. myopia

Explanation

The eye has a cornea — a clear, curved layer that protects it. If the cornea's shape is irregular, astigmatism results. People who have astigmatism see images as distorted, so they need to wear glasses or contact lenses. Sometimes people mistakenly say, "One of my eyes has a stigmatism." But the a in astigmatism is important to its meaning. The prefix a- means "without." Stigma is Greek for "point," so an eye that is "without point" is one that doesn't allow light rays to meet at a single point or focus. Since astigmatism is a condition, you don't need the article an before it: "My eye has astigmatism," not "My eye has an astigmatism."

Example Sentences

Astigmatism can be at least partially corrected with a spectacle having the opposite irregularity of the eye.

From Textbooks • Aug. 12, 2015

Astigmatism occurs because the cornea's curvature is not uniform, making both distant and nearby objects blurry.

From Time Magazine Archive

Astigmatism is usually laid to slight eye distortions.

From Time Magazine Archive

B. Astigmatism is detected by rotating the object glass or object glass cell.

From On Laboratory Arts by Threlfall, Richard

Astigmatism is corrected by a cylindrical lens, which is in fact a segment of a solid cylinder of glass.

From The Home Medical Library, Volume II (of VI) by Winslow, Kenelm