astigmatism
/əˈstɪɡmətɪz(ə)m
/noun [mass noun]
A defect in the eye or in a lens caused by a deviation from spherical curvature, which results in distorted images, as light rays are prevented from meeting at a common focus.Whether myopia, hyperopia or astigmatism is present, surgical correction attempts to redirect light rays to accommodate the refractive error....
- Side vision is distorted and oblique rays of light passing through a spherical lens produce astigmatism.
- Apart from testing the eye, they supply booklets detailing eye care with particular reference to refractive errors such as myopia, hypermetropia and astigmatism.
Derivatives
astigmatic
/ adjective ...- The astigmatic person does not know which focal line to look at, and hunting between the two may cause eyestrain.
- Monet, on seeing those fields, described them as ‘enough to drive a poor painter crazy - impossible to render with our poor colors,’ but render them he did in his astigmatic but beautiful way.
- Ordinary soft lenses tend to mould to the astigmatic curve, but special toric soft lenses are available for astigmatism.
Origin
Mid 19th century: from a-1 'without' + Greek stigma 'point' + -ism.