Hold the book up close and the words appear blurred. Push the book farther away, and the words snap back into sharp focus.
That's how most of us first recognize a condition called presbyopia, a name derived from Greek words meaning "old eye." Eye fatigue or headaches when doing close work, such as sewing, knitting or painting, are also common symptoms. Because it is associated with aging, presbyopia is often met with a groan -- and the realization that reading glasses or bifocals are inevitable
What causes presbyopia?
As we age, body tissues normally lose their elasticity. As skin ages, it becomes less elastic and we develop wrinkles. Similarly, as the lenses in our eyes lose some of their elasticity, they lose some of their ability to change focus for different distances. The loss is gradual. Long before we become aware that seeing close up is becoming more difficult, the lenses in our eyes have begun losing their ability to flatten and thicken. Only when the loss of elasticity impairs our vision to a noticeable degree do we recognize the change.
Recent research suggests that presbyopia occurs when the lens keeps growing as people get older and the ligaments become too slack for the muscles to work properly. This finding contrasts with the traditional view that aging cause the focusing muscles to become weaker and the lens to become more inflexible.
How does the loss of elasticity affect sight?
The crystalline lens plays a key role in focusing light on the retina. When we are young, the lens is flexible. With the help of tiny ciliary muscles, it changes shape, or accommodates, for both near and distant objects by bending or flattening out to help focus light rays. As we age, the lens becomes stiffer. Changing shape becomes more difficult. Not only does focusing on near objects become more difficult, the eye is also unable to adjust as quickly to rapid changes in focus on near and distant objects.
The flexibility of the lens begins to decrease in youth. The age at which presbyopia is first noticed varies, but it usually begins to interfere with near vision in the early 40's. Presbyopia affects everyone and there is no known prevention for it.
How is the problem diagnosed and treated?
An accurate, thorough description of symptoms and a comprehensive eye health examination, including a testing of the quality of your near vision, are necessary to diagnose presbyopia.
Usually, the treatment for presbyopia is prescription eyeglasses to help the eye accommodate for close-up work. Prescription lenses (reading glasses) help refract light rays more effectively to compensate for the loss of near vision.
If you do not have other vision problems, such as nearsightedness or astigmatism, you may only need glasses for reading or other tasks performed at a close range. If you have other refractive errors, such as nearsightedness, bifocal or progressive addition lenses (in which the power of the lens changes gradually towards the bottom to allow reading, without the reading portion of the bifocal lens being obviously visible) are often prescribed.
Can I still wear contact lenses?
Yes, you have three options with contact lenses: Bifocal contact lenses, monovision, and normal distance contact lenses with reading glasses. Generally, bifocal contact lenses are not as successful as the normal "single vision" ones.
What lens option will work best for me?
You will be asked a number of questions about your usual lifestyle or daily activities - to help determine the solution most suited to your needs. For instance, if you are a librarian, your needs will be significantly different from those of a truck driver or office worker.
Presbyopia is a gradual change, happening over a number of years so your prescription will need to be updated periodically. Changes are best made at your regular eye examination rather than after the need for change starts to cause you difficulties.