Definitions of astigmatism on the Web:a distortion of the image on the retina caused by irregularities in the cornea or lens.medical.preferredconsumer.com/laser_eye_surgeons/LASIK_glossary.htmlA warping of the curvature of the cornea so that light rays entering the eye do not meet in a single focal point, resulting in a distorted image.www.aces-abes.org/glossary.htmAn optical aberration resulting from unequal magnification across different diameters.www.astunit.com/tutorials/glossary.htm(uh-STIG-muh-tiz-um). Refractive error. Optical defect in which refractive power is not uniform in all directions (meridians). Light rays entering the eye are bent unequally by different meridians, which prevents formation of a sharp image focus on the retina. Slight uncorrected astigmatism may not cause symptoms, but a large amount may result in significant blurring and headache.www.howardnations.com/blindness/blindness_glossary.htmlAstigmatism means that the cornea is not spherical, or round, but rather has a different curvature at different points on the cornea. Think of an eye being shaped like a football, with the greatest, or steepest, amount of corneal curvature across the laces and the lesser, or flatter, corneal curvature across the end-to-end portion of the football. A normal eye is shaped like a basketball.www.valleylaser.com/Glossary.htmlIf the shape of the cornea is perfectly spherical there is no astigmatism. However, most corneas are not spherical but rather like the back side of a spoon. If you look at a spoon you see that the shape across the spoon is more curved than the shape along the spoon. The greater the difference between the two curves the more astigmatism. The amount of astigmatism is measured during an eye examination. Astigmatism can be corrected with Laser Vision Correction Techniques.www.citylaser.com/glossary.htmlAstigmatism blurs vision at all distances because the optical parts of the eye (cornea and lens) do not focus light onto the retina clearly. This condition is quite common, and results from an unequal curve of the cornea when comparing the horizontal and vertical planes. For descriptive purposes, imagine half of a tennis ball, squeezed at the top and bottom; the ball is now curved unequally. In the eye, this results in inaccurate focus on the retina. ...www.infantsee.org/x3635.xmlis always present if the corneal surface is different from the ideal ball-shape curvature. Further Informationwww.vsdar.de/english/lexikon/a.htmlCondition in which the cornea's curvature is asymmetrical (the eye is shaped like a football or egg instead of a baseball); light rays are focused at two points on the retina rather than one, resulting in blurred vision. Additional symptoms include distorted vision, eyestrain, shadows on letters, squinting and double vision. Read more about astigmatism.www.allaboutvision.com/resources/glossary.htmInstead of the front surface of the eye being round it is more oblong. This prevents the light being focused in the right way and leads to blurring. Astigmatism can be secondary to the shape of the cornea or the lens, and is usually correctable with spectacle or contact lenses.www.cochraneeyes.org/glossary.htma lens aberration that elongates images which change from a horizontal to a vertical position on opposite sides of best focus. It is generally associated with poorly made optics or collimation errors.www.astrostuff.com/OPTICAL_TERMS.htmA condition when the Cornea, (sometimes the lens) curves differently in different directions (a slice through a football). This causes objects (light) to bend differently to focus on the retina. The image is thus blurred, ghosted, or blurred unless corrected by contact lenses or spectacles.www.eyecaretyler.com/knowmore.htmAstigmatism is blurry vision produced by football-shaped corneas which are too steep in one place and too flat in another. Astigmatic corneas focus light in two different places in the eye, making both near and distance vision a problem.www.ascrs.org/eye/gloss.htmlAn irregular curvature of the cornea. If it is shaped more like a football rather than a basketball, light is not sharply focused on the retina. This results in blurry vision for both distance and near. LASIK can help correct this disorder.www.hollingsheadeyecenter.com/glossary.htmlA refractive problem that occurs when the surface of the cornea is uneven or structurally defective, preventing the light rays from converging at a point.www.bdid.com/termsa.htma condition in which the surface of the cornea is not spherical; causes a blurred image to be received at the retina. Condition can be corrected with glasses.www.schools.net.au/edu/lesson_ideas/optics/glossary.htmlA refractive error usually caused by toric (like a rugby ball) curvature of the front surface of the eye. Instead of being brought to a focus at one point at the back of the eye, light is focused in two lines at right angles to each other. Astigmatism is easily corrected with glasses to bring the two lines to one point focus.www.cf.ac.uk/optom/DownsSyndromeGroup/glossary.htmlThe aberration in which the horizontal and vertical lines are focused at different points along the optical axis.www.bi-optic.com/vocab.htmlirregularities in the shape of the cornea resulting in difficulties focusingwww.ski.org/AMNorcia_lab/General/terms.htmlA defect in optics in which a lens or mirror has two different amounts of curvature at 90 degrees to each other.home.earthlink.net/~dreyna14/glossary.htmA visual defect in which the unequal curvature of one or more refractive surfaces of the eye, usually the cornea, prevents light rays from focussing clearly at one point on the retina, resulting in blurred vision.www.keratoconus-group.org.uk/glossary.htmlthis is a form of vision problem that causes an image to be improperly reflected on the retina. This results from a misshapen cornea or lens.www.lasik-eye-surgery.info/explanation-of-terms.htmlresults from an irregularly-shaped or football-shaped cornea which causes light to refract ineffectively. Vision irregularities depend on the exact nature of the astigmatism.www.emoryhealthcare.org/departments/eye_center/sub_menu/glossary.htmlA condition where the cornea is irregularly shaped, causing distorted vision especially at near distances. Either glasses or toric contact lenses can correct astigmatism for most people. Small amounts of astigmatism may be correctable with regular oxygen permeable lenses.www.discounted-contact-lenses-online.com/glossary-contact-lens-terms-discounted-contact-lenses-online.htmis an optical aberration that spreads the image out into an ellipse or line. It can be caused by poorly made or mounted optics that distort the mirror or lens.www.telescopehouse.co.uk/page.aspx(ophthalmology) impaired eyesight resulting usually from irregular conformation of the cornea (optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point wordnet.princeton.edu/perl/webwnAstigmatism is a refraction error of the eye characterized by an aspherical cornea in which one axis of corneal steepness is greater than the perpendicular axis. Astigmatism causes difficulties in seeing fine detail, and can be often corrected by glasses with a cylindrical lens (i.e. a lens that has different radii of curvature in different planes), contact lenses, or refractive surgery. en.wikipedia.org/wiki/Astigmatism