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astigmatism - 8 dictionary results
a⋅stig⋅ma⋅tism
[uh-stig-muh-tiz-uh
m] 
–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. |
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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Based on the Random House Dictionary, © Random House, Inc. 2009.
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Link To astigmatism
| a·stig·ma·tism (ə-stĭg'mə-tĭz'əm) n. 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 blurred vision. [a-1 + Greek stigma, stigmat-, point (from stizein, stig-, to tattoo; see steig- in Indo-European roots).] as'tig·mat'ic (ās'tĭg-māt'ĭk) adj. & n., as'tig·mat'i·cal·ly adv. |
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Astigmatism
A*stig"ma*tism\, n. [Gr. 'a priv. + ?, ?, a prick of a pointed instrument, a spot, fr. ? to prick: cf. F. astigmatisme.] (Med. & Opt.) A defect of the eye or of a lens, in consequence of which the rays derived from one point are not brought to a single focal point, thus causing imperfect images or indistinctness of vision. Note: The term is applied especially to the defect causing images of lines having a certain direction to be indistinct, or imperfectly seen, while those of lines transverse to the former are distinct, or clearly seen.
Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
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The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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astigmatism
coined (in form astigmatic) 1849 by English scientist William Whewell (1794-1866), from Gk. a- "without" + stigmatos gen. of stigma "a mark, spot, puncture."
Online Etymology Dictionary, © 2001 Douglas Harper
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Main Entry: astig·ma·tism
Pronunciation: &-'stig-m&-"tiz-&m
Function: noun
1 : a defect of an optical system (as a lens)causing rays from a point to fail to meet in a focal point resulting in a blurred and imperfect image
2 : a defect of vision due to astigmatism of the refractive system of the eyeand especially to corneal irregularity —compare EMMETROPIA,
Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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astigmatism a·stig·ma·tism (ə-stĭg'mə-tĭz'əm)
n.
A condition in which unequal curvatures along the different meridians in one or more of the refractive surfaces of the eye cause the rays from a light source not to be focused at a single point on the retina. Also called astigmia.
as'tig·mat'ic (ās'tĭg-māt'ĭk) adj. & n.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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astigmatism (ə-stĭg'mə-tĭz'əm) Pronunciation Key
(click for larger image in new window) 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. |
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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