presbyopia

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Presbyopia

 

Definition

The term presbyopia means "old eye" and is a vision condition involving the loss of the eye's ability to focus on close objects.

Description

Presbyopia is a condition that occurs as a part of normal aging and is not considered to be an eye disease. The process occurs gradually over a number of years. Symptoms are usually noticeable by age 40-45 and continue to develop until the process stabilizes some 10-20 years later. Presbyopia occurs without regard to other eye conditions.

Causes and symptoms

In the eye, the crystalline lens is located just behind the iris and the pupil. Tiny ciliary muscles pull and push the lens, adjusting its curvature, and thereby adjusting the eye's focal power to bring objects into focus. As individuals age, the lens becomes less flexible and elastic, and the muscles become less powerful. Because these changes result in inadequate adjustment of the lens of the eye for various distances, objects that are close will appear blurry. The major cause of presbyopia is loss of elasticity of the lens of the eye. Loss of ciliary muscle power, however, is also believed to contribute to the problem.
Symptoms of presbyopia result in the inability to focus on objects close at hand. As the lens hardens, it is unable to focus the rays of light that come from nearby objects. Individuals typically have difficulty reading small print, such as that in telephone directories and newspaper advertisements, and may need to hold reading materials at arm's length. Symptoms include headache and eyestrain when doing close work, blurry vision, and eye fatigue. Symptoms may be worse early in the morning or when individuals are fatigued. Dim lighting may also aggravate the problem.

Diagnosis

Presbyopia is officially diagnosed during an eye examination conducted by eye specialists, such as optometrists or ophthalmologists. After completing optometric college, doctors of optometry screen patients for eye problems and prescribe glasses and contact lenses. In contrast, ophthalmologists are medical doctors who specialize in eye diseases. They perform eye surgery, treat eye diseases, and also prescribe glasses and contact lenses.
A comprehensive eye examination requires at least 30 minutes. Part of the examination will assess vision while reading by using various strength lenses. If the pupils are dilated with drugs to permit a thorough examination of the retina, an additional hour is required. The cost of eye examinations can range from $40 to $250 depending on the complexity and site of the examination and the qualifications and reputation of the examiner. Some insurers cover the cost of routine eye examinations, while others do not. A thorough eye examination is recommended at regular intervals during the adult and aging years to monitor and diagnose eye conditions. However, individuals frequently self-diagnose presbyopia by trying on inexpensive mass-produced reading glasses until they find a pair that permits reading without strain.

Treatment

Presbyopia cannot be cured, but individuals can compensate for it by wearing reading, bifocal, or trifocal eyeglasses. A convex lens is used to make up for the lost automatic focusing power of the eye. Half-glasses can be worn, which leave the top open and uncorrected for distance vision. Bifocals achieve the same goal by allowing correction of other refractive errors (improper focusing of images on the retina of the eye).
In addition to glasses, contact lenses have also been found to be useful in the treatment of presbyopia. The two common types of contact lenses prescribed for this condition are bifocal and monovision contact lenses. Bifocal contact lenses are similar to bifocal glasses. The top portion of the lens serves as the distance lens while the lower serves as the near vision lens. To prevent rotation while in the eye, bifocal contacts use a specially manufactured type of lens. Good candidates for bifocal lenses are those patients who have a good tear film (moist eyes), good binocular vision (ability to focus both eyes together) and visual acuity in each eye, and no disease or abnormalities in the eyelids. The bifocal contact lens wearer must be motivated to invest the time it requires to maintain contact lenses and be involved in occupations that do not impose high visual demands. Further, bifocal contact lenses may limit binocular vision. Bifocal contact lenses are relatively expensive, in part due to the time it takes the patient to be accurately fitted.
An alternative to wearing eyeglasses or bifocal contact lenses is monovision contact lenses. Monovision fitting provides one contact lens that corrects for near vision and a second contact lens for the alternate eye that corrects for distance vision. If distance vision is normal, the individual wears only a single contact lens for near vision. Monovision works by having one eye focus for distant objects while the other eye becomes the reading eye. The brain learns to adapt to this and will automatically use the correct eye depending on the location of material in view. Advantages of monovision are patient acceptability, convenience, and lower cost.
Several problems exist with the use of contact lenses in the treatment of presbyopia. Some individuals experience headache and fatigue during the adjustment period or find the slight decrease in visual acuity unacceptable. Monovision contact lenses usually result in a small reduction in high-contrast visual acuity when compared with bifocal contact lenses.

Prognosis

The changes in vision due to aging usually start in a person's early 40s and continue for several decades. At some point, there is no further development of presbyopia, as the ability to accommodate is virtually gone.

Prevention

There is no known way to prevent presbyopia.

Resources

Organizations

American Academy of Ophthalmology. 655 Beach Street, P.O. Box 7424, San Francisco, CA 94120-7424. http://www.eyenet.org.
American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. http://www.aoanet.org.
Lighthouse National Center for Vision and Aging. 111 E. 59th St., New York, NY 10022. (800) 334-5497. http://www.lighthouse.org.
National Eye Institute. 2020 Vision Place, Bethesda, MD 20892-3655. (301) 496-5248. http://www.nei.nih.gov.

Key terms

Accommodation — The ability of the eye to change its focus from near to distant objects.
Binocular vision — Using both eyes at the same time to see an image.
Ciliary muscles — The small muscles that permit the lens to change its shape in order to focus on near or distant objects.
Lens (or crystalline lens) — The eye structure behind the iris and pupil that helps focus light on the retina.
Visual acuity — Sharpness or clearness of vision.

presbyopia

 [pres″be-o´pe-ah]
diminution of accommodation of the lens of the eye occurring normally with aging, and usually resulting in hyperopia, or farsightedness. adj., adj presbyop´ic. Presbyopia is caused by a loss of elasticity in the crystalline lens of the eye. The lens focuses images on the retina with the aid of muscles that stretch it to make it less convex or relax it to make it more spherical and thus more convex. As it ages, the lens may lose its ability to become convex enough to accommodate to nearby objects. This condition usually begins around the age of 40. Presbyopia can most often be comfortably corrected through the use of eyeglasses.

pres·by·o·pi·a (Pr),

(prez'bē-ō'pē-ă),
The physiologic loss of accommodation in the eyes in advancing age, said to begin when the near point has receded beyond 22 cm (9 inches).
[presby- + G. ōps, eye]

presbyopia

/pres·by·opia/ (Pr) (-o´pe-ah) diminution of accommodation of the lens of the eye occurring normally with aging.presbyop´ic

presbyopia

(prĕz′bē-ō′pē-ə, prĕs′-)
n.
Inability of the eye to focus sharply on nearby objects, resulting from loss of elasticity of the crystalline lens with advancing age.

pres′by·op′ic (-ŏp′ĭk, -ō′pĭk) adj.

presbyopia

[prez′bē·ō′pē·ə]
Etymology: Gk, presbys + ops, eye
a refractive condition in which the accommodative ability of the eye cannot meet the accommodative demand for near work. It results from a loss of elasticity of the lens of the eye. The condition commonly develops with advancing age, with the first symptoms appearing about age 40. Compare visual accommodation. presbyopic, adj.

presbyopia

Old eyes Ophthalmology The gradual loss of the lens's ability to accommodate–for near objects, due to ↓ elasticity, associated with aging; occurs in almost all people > age 45

pres·by·o·pi·a

(Pr) (prez'bē-ō'pē-ă)
The physiologic loss of accommodation in the eyes in advancing age, said to begin when the near point has receded beyond 22 cm (9 inches).
[presby- + G. ōps, eye]

presbyopia

Progressive loss of focusing power of the eyes associated with loss of elasticity of the internal (crystalline) lenses. The condition is closely age-related and the effect is to make close work, such as reading, increasingly difficult. The term derives from the Greek presbys , an old man, and ops , an eye.

presbyopia

a loss of ACCOMMODATION (focusing ability) in the eye that occurs frequently in older humans due to a loss of elasticity in the lens. Such affected individuals require two corrective lenses, one for close work, the other for viewing distant objects.

presbyopia 

A refractive condition in which the accommodative ability of the eye is insufficient for near vision work, due to ageing. This is due to a hardening of the lens and a reduction of the elasticity of its capsule. The main symptom is blurred vision, or difficulty in sustaining clear vision, at the working distance. It is corrected by positive lenses (called the addition). This condition usually occurs when the amplitude of accommodation has decreased to 4 D. It generally occurs between the age of 42 and 48 in people living in European and North American countries. People living in hot climates become presbyopic earlier. Syn. old sight (colloquial). See near addition; crystalline lens capsule; reading distance; hyperchromatic lens; progressive lens; modulus of elasticity; monovision.

pres·by·o·pi·a

(prez'bē-ō'pē-ă)
The physiologic loss of accommodation in the eyes in advancing age.
[presby- + G. ōps, eye]

presbyopia (prez´bīo´pēə),

n a form of optical distortion affecting the vision of patients, particularly those of advancing age. It depends on diminution of the power of the accommodation of the lens as a result of loss of elasticity of the crystalline lens, causing the near point of distinct vision to be removed farther from the eye.

presbyopia

diminution of visual acuity due to old age; caused by loss of accommodation resulting from decreased elasticity of the lens.