Sunday, January 15, 2006

hyperopia (far-sightedness)

The hyperopic eye is one that is deficient in refractive power so that rays of light from a distant object come to a focus at a point behind the retina with respect to the unaccommodated eye.
In most hyperopia, the chief cause is a shortening of the length of the eye. Such an eye is smaller than the normal eye and is called axial hyperopia. Another cause of hyperopia is found when the cornea or lens has less curvature than normal so that the image formed is focused at a point behind the normally placed retina. This is called curvature hyperopia. The third cause of hyperopia is a change of the refractive power of the lens, which can occur with age or in diabetes. This is called index hyperopia. It is usually in older people that the symptoms of hyperopia become apparent, as educational demands and the time alloted for close work increase. Symptoms of hyperopia are the inability to see well closely at a young age. Other symptoms include headaches, burning of the eyes, a pulling sensation, and eyestrain. These symptoms are generally related to the constant excessive accommodation that is required for close work in a hyperope. In older people no symptoms may appear until the power of accomodation has diminished to the extent that the near point is beyond the range of comfortable reading distance. The treatment of hyperopia involves the use of convex-lens, spectacles or contact lens. Older people, particularly those between 55 and 65 years of age, find it difficult to accommodate. This type of hyperopic patient usually needs convex lenses for both distance vision and close work.
See also ASTIGMATISM; 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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