Sunday, December 11, 2005

astigmatism

astigmatism - Astigmatism is the condition in which rays of light in the eye are not refracted equally in all directions, so that a point focus on the retina is not attained. In most instances astigmatism occurs because the radius of curvature of the cornea is not equal in all directions; this is called corneal astigmatism. Astigmatism can also occur as a result of tight suturing following an intraocular surgery, such as cataract surgery. Since over one million cataract surgeries are performed each year in the United States on the elderly, the incidence of astigmatism is greater in this age group than in others. While the hyperopic person can normally see efficiently at a distance and the myopic person sees well close up, the person with astigmatism most often complains of an inability to see well either at a distance or near without glasses.
Treatment of astigmatism usually involves wearing glasses with a corrective lens. A surgical procedure is available to help correct astigmatism.
See also HYPEROPIA; MYOPIA; AND PRESBYOPIA. Newell, F. W. Ophthalmology Principles and Concepts, 6th ed.  St. Louis: C. V. Mosby Co., 1986.
Slatt, B. J .. and Stein, H. A. The Ophthalmic Assistant: Fundamentals and Clinical Practice, 4th ed. St. Louis: C. V. Mosby Co., 1983.


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