Presbyopia

What Is It?

Presbyopia is the progressive inability of the lens of the eye to change shape and focus clearly on near objects. No one knows exactly what causes the lens to become inflexible, but it happens to everyone as a natural part of aging.

In order for us to see images clearly, light rays enter the eye, where the lens bends and focuses the rays on the retina. The lens changes shape to accommodate the differences in light coming from objects at different distances. Beginning early in life — perhaps as early as age 10 — our lenses gradually stiffen and lose the ability to change shape. By the time we are in our 40s, the stiffness has progressed to the point that light rays from close objects cannot be focused properly, and we begin to experience blurred vision when we try to do tasks that require up-close focus, such as reading or needlework. The lens continues to stiffen until about age 65, when nearly all elasticity has been lost.

Presbyopia eventually affects everyone, even people who are already farsighted (hyperopic) or nearsighted (myopic). Because people who are farsighted already have difficulty focusing on near objects, they may experience presbyopia a little earlier in life. People who are nearsighted may find that their distance vision improves slightly, and may experience presbyopia a few years later in life.

Symptoms

Presbyopia causes the following symptoms:

• Words appear blurred at a previously comfortable reading distance
• Needing to hold reading material or other objects farther away from your eyes to gain clarity or see details
• Needing brighter light to see clearly — Bright light constricts the pupils, which changes the focus of the light on the retina.
• Difficulty reading late at night, or when you are tired or stressed
• Eye discomfort, fatigue or drowsiness when doing close work because of the strain of eye muscles working to change the lens shape.
• Possible headaches as a result of muscle tension

Diagnosis

Many people over age 40 self-diagnose presbyopia based on their inability to read clearly at a distance that used to be natural and comfortable. Because the condition comes on gradually over many years, most people don't notice small vision changes and delay seeking professional help until the focusing problems interfere with daily life. Many optometrists joke that patients seek help only when their arms become "too short," unable to hold printed pages far enough away to see clearly.

Presbyopia can be diagnosed by an optometrist, ophthalmologist or physician, who will take a complete medical history to determine the extent of your vision problem. He or she will test your vision by having you read text at a distance that is typically comfortable to you. If the doctor diagnoses presbyopia, he or she will do a test to determine the extent of the focusing problem and the appropriate lens prescription. In this test, the doctor has you look through corrective lenses, and continues to increase the magnification power until the words on the page are clear to you and you are comfortable reading.