astigmatism

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astigmatism
top: normal eye with light focusing on the retina
bottom: astigmatic eye with light focusing in different places on or in front of the retina

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- + Greek stigma, stigmat-, point (from stizein, stig-, to tattoo; see steig- in Indo-European roots).]

as′tig·mat′ic (ăs′tĭg-măt′ĭk) adj. & n.
as′tig·mat′i·cal·ly adv.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

astigmatism

(əˈstɪɡməˌtɪzəm) or

astigmia

n
1. (General Physics) 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. (Pathology) faulty vision resulting from defective curvature of the cornea or lens of the eye
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

a•stig•ma•tism

(əˈstɪg məˌtɪz əm)

n.
1. Also called a•stig•mi•a (əˈstɪg mi ə) 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. an aberration of a lens or other optical system in which the image of a point is spread out along the axis.
[1840–50]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

a·stig·ma·tism

(ə-stĭg′mə-tĭz′əm)
A defect of the eye in which the curvature of the cornea or lens is uneven. This prevents rays of light from being focused at a single point on the retina, resulting in indistinct or imperfect images.
The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

astigmatism

a defect in a lens, eye, or mirror that causes rays from one direction not to focus at one point. — astigmatic, adj.
See also: Eyes
-Ologies & -Isms. Copyright 2008 The Gale Group, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.astigmatism - (ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea; common in nearsighted people
ophthalmology - the branch of medicine concerned with the eye and its diseases
ametropia - (ophthalmology) faulty refraction of light rays in the eye as in astigmatism or myopia
keratectasia - abnormal bulging of the cornea of the eye
keratoconus - abnormal cone-shaped protrusion of the cornea of the eye; can be treated by epikeratophakia
2.astigmatism - (optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point
optics - the branch of physics that studies the physical properties of light
condition, status - a state at a particular time; "a condition (or state) of disrepair"; "the current status of the arms negotiations"
stigmatism - (optics) condition of an optical system (as a lens) in which light rays from a single point converge in a single focal point
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
Translations

astigmatism

[æsˈtɪgmətɪzəm] Nastigmatismo m
Collins Spanish Dictionary - Complete and Unabridged 8th Edition 2005 © William Collins Sons & Co. Ltd. 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005

astigmatism

[əˈstɪgmətɪzəm] nastigmatisme m
Collins English/French Electronic Resource. © HarperCollins Publishers 2005

astigmatism

Collins German Dictionary – Complete and Unabridged 7th Edition 2005. © William Collins Sons & Co. Ltd. 1980 © HarperCollins Publishers 1991, 1997, 1999, 2004, 2005, 2007

astigmatism

[æsˈtɪgmətɪzm] nastigmatismo
Collins Italian Dictionary 1st Edition © HarperCollins Publishers 1995

a·stig·ma·tism

[MIM*603047]
n. astigmatismo, defecto de la visión a causa de una irregularidad en la curvatura del ojo.
English-Spanish Medical Dictionary © Farlex 2012

astigmatism

n astigmatismo
English-Spanish/Spanish-English Medical Dictionary Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
References in periodicals archive ?
This study only analyzed the changes of total higher-order aberrations, total coma aberration, total spherical aberration, and total trefoil aberration corresponding to the RMS value in the children with with-the-rule astigmatism. HOAs are affected by many factors including pupil size [2, 5, 14], age [15-17], and accommodation.
simK overestimates TCRP (mean 0.11 [+ or -] 0.22 D) in the eyes with with-the-rule astigmatism, and simK underestimates TCRP (mean 0.26 [+ or -] 0.31 D) in the eyes with against-the-rule astigmatism.
Pipat Kongsap (11) documented that a superior scleral incision was associated with slight against-the-rule astigmatism (flatter vertical axis), while a temporal scleral incision was associated with slight with-the-rule astigmatism (flatter horizontal axis).