Presbyopia

Definition

The term presbyopia means "older 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. The condition develops gradually over a number of years. Symptoms are usually noticeable by age 40 to 45, and continue to develop until the process stabilizes some 10 or 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 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 and loss of elasticity of the zonules that connect the ciliary muscle to the lens, however, are 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 near 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 optometrists (O. D. s) or ophthalmologists (M. D. s).

O.D.s or M.D.s, with the help of ophthalmic assistants, should perform a comprehensive eye exam to diagnose the condition. The assistant should take a detailed patient history prior to the exam. This is especially important when diagnosing premature presbyopia.

The optometrist or ophthalmologist, or in some cases a highly trained assistant, will begin the ocular examination by testing visual acuity and refraction. During the exam the clinician will also determine ocular motility and alignment, nearpoint of convergence, near fusional vergence amplitudes, relative accommodation measurements, accommodative amplitude and facility of accommodation.

To further determine presbyopia, the clinician should perform near retinoscopy and intermediate distance testing, which can be performed with a phoropter or trial lens.

There are five different types of presbyopia:

• Incipient presbyopia is the earliest stage in which symptoms are documented. Usually the patient has trouble reading small print, but may perform well on testing and may actually reject a near vision prescription.
• Functional presbyopia is the point at which patients usually notice the difficulties with near vision. The age when this occurs varies and depends on environment, task requirements, nutrition, or general health.
• Absolute presbyopia is the result of continuous gradual decline in accommodation, and is the next phase after functional presbyopia. At this stage, little accommodative ability remains.
• Premature presbyopia is the appearance of the disease at an earlier age than expected because of nutritional, environmental, or disease-related causes. Pharmaceuticals may also be a cause of premature presbyopia.
• Nocturnal presbyopia occurs when accommodation decreases in low-light conditions.

Content licensed from:

Author Info: Mary Bekker, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Nursing and Allied Health, 2002

This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.