Sunday, January 15, 2006

refractive errors

The normal condition of the eye in which, with no accommodation, parallel light is focused on the retina is emmetropia. Any optical departure from this condition is called a refractive error. Refractive errors cause a decrease in visual acuity and include presbyopia, myopia, astigmatism, and hyperopia. Of these the first three may occur at any time in life although their incidence tends to increase with age. The refractive error that is seen almost universally with aging is presbyopia.
See also ASTIGMATISM; HYPEROPIA; MYOPIA; 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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