Pursuing 20/20 at 40+ : Part 2

by Food and Drug Administration (FDA)

(Page 2 of 2)

Progressive Addition Lenses

Bifocals and trifocals wearers who are bothered by the telltale lines on these glasses may want to consider getting what are known as progressive addition lenses. These eyeglasses give a gradual invisible change in lens power from the top of the lens to the bottom. To get clear vision from far to near distance, you move your eyes up or down.

Progressive addition lenses cost about $25 to $50 more than bifocals, and adjustment to them is more difficult. The main problem these lenses pose is distortion in the peripheral areas of the lenses. If wearers have to look through the edges of their lenses in order to see someone beside them, for example, the person may appear blurred. The amount of blurring experienced can be limited, however, by turning the head rather than the eyes to look at something not directly in front.

The distortion on the periphery of progressive addition lenses may also be spatially disorienting. People who use these glasses for the first time may feel they are moving up or down hill when in fact they are on level ground, says Lippman. The distortion on the sides may increase the more complex the prescription is for other vision problems besides presbyopia, such as astigmatism or nearsightedness. Lippman recommends that only properly motivated people who understand the limitations of these lenses consider using them as an alternative to conventional bifocals or trifocals.

Contact Lenses

Those who prefer contact lenses to glasses may not have to give them up when presbyopia strikes. Many people find they can continue to wear their regular contacts for distance vision and put on reading glasses for close work. Because the prescription for these glasses is determined, in part, by the prescription for the contact lenses, the reading glasses alone cannot provide good close vision.

Hard, gas-permeable, and soft contact lenses are all available with bifocal corrections. Bifocal contacts come in a variety of designs. Working with an eye-care professional, consumers can decide which option will work best for them based on individual vision needs, eye shape, and other factors.

It is harder to adjust to multifocal contact lenses than to multifocal eyeglasses. Fewer than one 1 of 3 people using bifocal contacts, for example, is able to adjust to them, whereas most people can adjust to bifocal eyeglasses. Because of this difficulty, most practitioners usually recommend bifocal contacts only to people who have successfully worn contacts in the past.

Multifocal contacts can be double or triple the price of multifocal eyeglasses. A much less costly contact lens alternative is to fit one eye with a contact lens for near vision and, if needed, the other eye with a lens for distance vision. Contacts worn in this way are referred to as monovision lenses. They cost about the same as regular contacts and are easier to replace or change. However, contacts worn in this manner may hamper depth perception and peripheral vision. I wouldn't want to fly a plane with them, Lippman says. Monovision contact lenses work more successfully in people whose normal vision lacks fusion?that is, their eyes do not work together properly.

The greater difference there is between the prescriptions for far and near vision, the harder it is to adjust to this manner of wearing contact lenses. In people with early stages of presbyopia, the difference is not that great, but as you get older, monovision contacts are less of an option, Lippman says.

New on the market are diffractive contact lenses. The surface of these lenses has invisible ridges molded into concentric circles. The space between the circles gets smaller as the distance increases from the center of the lens, which is used for distance vision. The ridges bend light in such a way that the wearer is able to see things both close and far alternatively. Consequently, a person using diffractive contacts doesn't have a narrowed area on the lens in which to look to see far or near, as with bifocal lenses. Wearers must learn to adjust to diffractive contacts, however, and since they are relatively new, it's too early to tell how successful these contact lenses will be. They are more expensive than bifocal contacts.

Whether opting for reading glasses, multifocal lenses, or contacts, wearers usually need new ones every 12 to 18 months to correct for worsening presbyopia. It doesn't pay to get old, says Lippman. My advice is to stay young.

Adjustment Tips

To get the best results with your bifocal or trifocal eyeglasses, let your eye doctor know all the various tasks you do both on and off the job that require clear vision. This information will help in the correct placement of the various lens prescriptions. Improperly placed lens segments can make seeing difficult and cause accidents, particularly when walking, using stairs, or driving.

The American Optometric Association offers these suggestions to new bifocal and trifocal wearers:

Don't look at your feet when walking. Hold reading material closer to your body and lower your eyes, not your head, so that you are reading out of the lowest part of the lens. Fold the newspaper in half or quarters and move it, rather than your head, to read comfortably.

Wear the lenses continuously for the first week or two, until you are accustomed to them, even though you may not need them for all tasks. Make sure that eyeglass frames are always adjusted for your face so that the lenses are properly positioned.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.