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 ?
04 Which of the following is true regarding the corneal astigmatism shown in the topographies?
Among their topics are posterior corneal astigmatism: basics and clinical implication, considerations in cataract surgery following postrefractive error correction, malpositioned intraocular lens and capsular bag: intraocular lens complex issues, bilensectomy: phakic intraocular lens explantation with coincidental cataract surgery and intraocular lens implantation, and telescopic intraocular lenses.
Material and Methods: Sixty eyes undergoing cataract surgery with already existing corneal astigmatism of at least 0.5 diopter (D) were included in the study.
Pre-existing corneal astigmatism of more than 1 D is present in almost 1/3rd of cataract patients undergoing surgery, 22% having > 1.5 D of astigmatism, 8 % of them > 2.0 D of corneal astigmatism.
Comparability and repeatability of corneal astigmatism measurements using different measurement technologies.
Many studies have demonstrated that some ocular biometric characteristics, such as increased AL, reduced corneal curvature, and high corneal astigmatism, have potential diagnostic values in MFS patients [8-10, 19-22].
Today, cataract surgery is regarded as a refractive surgery, promises rapid visual rehabilitation and pseudophakic emmetropia, which makes eliminating corneal astigmatism critical.
The keratometry readings determine the nature and extent of corneal astigmatism.
Radial keratotomy (RK) is an old procedure invented in 1974 by Svyatoslav Fyodorov aimed to correct myopia and corneal astigmatism [1].