astigmatism

[ uh-stig-muh-tiz-uhm ]

noun

1. Also called a·stig·mi·a [uh, -, stig, -mee-, uh]. 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.

astigmatism

/ 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

astigmatism

/ 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.

astigmatism

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.

Word History and Origins

Origin of astigmatism¹

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

Example Sentences

When a child holds his head to one side constantly on looking at objects, astigmatism, an error of eyesight, is usually indicated.

From Project Gutenberg

This is usually attributed to the presence of an irregular astigmatism situated near the asymmetric meridian.

From Project Gutenberg

If the subject cannot read up to the twenty-foot line, nearsightedness or astigmatism is indicated.

From Project Gutenberg

Short sight or long sight is often associated with astigmatism, so that suitable spectacles cannot be very easily provided.

From Project Gutenberg

If the lines appear with unequal distinctness, some irregularity of refraction (astigmatism) is indicated.

From Project Gutenberg