ASTIGMATISM
Astigmatism
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances. The term comes from the Greek α- meaning "without" and στίγμα, "a mark, spot, puncture".The above text is a snippet from Wikipedia: Astigmatism
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astigmatism
Noun
- A defect of a lens such that light rays coming from a point do not meet at a focal point so that the image is blurred.
- A disorder of the vision, usually due to a misshapen cornea, such that light does not focus correctly on the retina causing a blurred image.
The above text is a snippet from Wiktionary: astigmatism
and as such is available under the Creative Commons Attribution/Share-Alike License.