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- Corneal astigmatism is when the cornea is misshaped.
- Lenticular astigmatism is when the lens is misshaped.
|Normal Anatomy of the Eye|
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- Heredity—a family history of astigmatism, eye disease, or disorders such as keratoconus
- Eye surgery—certain types of eye surgery, such as cataract (lens of the eyes are cloudy) removal (less common with modern techniques)
- A history of corneal scarring or thinning
- A history of excessive nearsightedness (a visual defect where distant objects appear blurred) or farsightedness (a visual defect where distant objects are seen better than objects that are close)
- Blurred (objects appear fuzzy) or distorted (objects appear twisted or out of focus) vision
- Excessive squinting or closing of the eyes
- Visual acuity assessment test (VAT)—this test is used to measure how well you can distinguish different size letters or symbols (very large to very small) at a specific distance
- Refractor test—this test uses a refractor, a special instrument that has interchangeable lenses of different strengths to measure how well you see objects at various distances. The ophthalmologist or optometrist will ask you to look through the lens and read a chart that is several feet away. The ophthalmologist or optometrist will adjust the strength of the lens based on your responses.
- Keratoscope—a device used to detect and measure the presence of corneal surface curvature
Photorefractive keratectomy (PRK)
- Laser beams are used to reshape the abnormal or irregular curve of the cornea.
- Laser in situ Keratomileusis (LASIK) (a type of PRK)—laser beam to reshape the curve of the cornea by removing corneal tissue.
- Radical keratotomy (RK)—Small incisions (cuts) are made partial thickness into the cornea.
- Laser-assisted subepithelial Keratomileusis (LASEK)—This procedure is not as commonly used; however, it may offer additional benefits especially for patients with thin corneas or at high risk of an eye injury.
American Optometric Association http://www.aoa.org
Astigmatism Mayo Clinic http://www.mayoclinic.com/health/astigmatism/DS00230/DSECTION=3
National Eye Institute (NEI) http://www.nei.nih.gov
Prevent Blindness America http://www.preventblindness.org
Canadian Ophthalmological Society http://www.eyesite.ca
The Canadian National Institute for the Blind http://www.cnib.ca
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- Reviewer: Michael Woods, MD
- Review Date: 06/2013
- Update Date: 06/30/2013