A common form of visual impairment in which part of an image is blurred due to an irregularity in the dome-shaped curvature of the front surface of the eye, the cornea. With astigmatism, light rays entering the eye are not uniformly focused on the retina. The result is blurred vision at all distances. Significant astigmatism can cause headaches, ey [..]

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.) [..]

One of Seidel's five aberrations. Astigmatism is an aberration that causes points to blur, degrading sharpness. It can be reduced but not eliminated by stopping down the lens.

A condition where there is deviation in the curvature of the eye or the lens. This means that vision is distorted, as light rays cannot focus properly.

Failure of an optical system, such as a lens or a mirror, to image a point source of light as a single point.

n. a visual disorder that occurs when the light rays of a visual stimulus do not all focus on a single point on the retina. Astigmatism is generally caused by uneven curvature of the cornea. As a resu [..]

A misshape of the eye, where vision is blurred by an irregularly shaped cornea. The cornea, instead of being shaped like a sphere, is ellipsoidal (like an egg) and reduces the cornea’s ability to focus light.

(uh-STIG-muh-tiz-um). Optical defect in which refractive power is not uniform in all directions (meridians). Light rays entering the eye are bent unequally by different meridians, which prevents forma [..]

An eye disorder caused by uneven curvature of the eyeball that motivates light rays to bend, targeting more than one point of the retina, instead of a single spot. This causes blurry vision, vague sha [..]

(n) (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people(n) (optics) defect in an optical system in which light rays from a singl [..]

Astigmatism is the most common vision problem. It’s caused by an irregularly shaped cornea and results in a mismatched focussing horizontally and vertically.

An irregularity in the curvature of the lens of the eye, resulting in a blurry or distorted image.

A condition in which the surface of the cornea is not spherical, but is irregularly shaped like the back of a spoon. An astigmatic cornea causes light images to focus on two separate points in the eye, creating a distorted image. Symptoms range from visual discomfort in mild cases, to severe blurring, ghosting, and distortion similar to a reflectio [..]

Blurry vision caused by an irregular curve in the cornea of the eye.

( a=negative + Gr. stigma=point ) A refractive abnormality where light is not focused to a point on the retina. This is often caused by the cornea or front window of the eye being ellipt [..]

Unequal refractive power of the eye (19thC)

If you take a good look at your eye, you might barely see your cornea, the clear outer covering of the eye. For someone with astigmatism, the cornea is uneven, which changes how light enters the eye a [..]

One of Seidel's five aberrations. Astigmatism is an aberration that causes points to blur, degrading sharpness. It can be reduced but not eliminated by stopping down the lens.

lens aberration making a single point light source impossible to focus as a true point.

Unequal curvature of the refractive surfaces of the eye. Thus a point source of Light cannot be brought to a point focus on the Retina but is spread over a more or less diffuse area. This results from [..]

Unequal curvature of the refractive surfaces of the eye. Thus a point source of light cannot be brought to a point focus on the retina but is spread over a more or less diffuse area. This results from [..]

A defect of a lens which causes the image of a point to appear as a line, rather than a point.

A vision condition that causes blurred vision due either to the irregular shape of the cornea (the clear front cover of the eye) or sometimes the curvature of the lens inside the eye.

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 one point on the retina, resulting in blu [..]

A vision problem that results in blurred images.

An aberration of a lens with spherical surfaces such that the image of a point not lying on the optical axis is a pair of short lines normal to each other and at slightly different distances from the [..]