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Bye-bye bifocals: New approaches to aging eyes

graphic

March 27, 2000
Web posted at: 11:41 a.m. EST (1641 GMT)


In this story:

How the eye works

Beyond granny glasses

On the horizon

RELATED STORIES, SITES icon



(WebMD) -- First the print in the telephone book seems to get smaller. Then the newpaper text turns fuzzy. Worse yet, you discover one evening that you can't read the menu in your favorite restaurant.

If these experiences sound familiar -- and you happen to be forty-something -- you're not alone. Many members of the boomer generation are passing through the prime years for presbyopia (meaning "aging eyes"). This loss of focusing ability can start as early as 35 or as late as 50. Usually, it stops progressing at about age 60.

When younger, many boomers might have worn granny glasses as a fashion statement. But now reading glasses, or old-fashioned bifocals, don't seem quite as hip, and many visually impaired people in their forties are turning to other alternatives, such as bifocal contact lenses or eye surgery. Soon there may be additional options, as companies and researchers race to find other alternatives to keep boomers feeling young.

How the eye works

To understand presbyopia, you need to understand how the eye works. In order to focus light from different distances properly onto the retina -- which acts like the film in a camera and "develops" the images we see -- the lens of the human eye adjusts its shape as it responds to tiny muscles in the eye. The more the lens can be "bent" by the muscles, the closer up the eye can focus.

Just as the rest of the body ages, so does the lens, becoming less flexible as time goes by. When the lens doesn't bend as well as it once did, the distance at which we can see clearly gets farther and farther away, says Raymond I. Myers, O.D., an associate clinical professor at the University of Missouri-St. Louis.

The simplest way to think about it is that the lens within your eye is becoming harder as you add birthdays, says Rodney Tahran, O.D., of Dallas, Texas. And this phenomenon is what leaves people in their forties squinting in restaurants, holding their menus at arm's length. At first, they may try to compensate by adjusting their reading distance, but at some point this no longer works.

By age 45, almost everyone notices a decline in close vision. While some people may choose to go without eyeglasses if their lifestyle doesn't require a lot of reading, that solution doesn't work for most people.

Some, of course, will have already dealt with changes in their vision. People with farsightedness (hyperopia) often need help with their close vision early on, while people with nearsightedness (myopia) might find their close vision improves slightly through their 40s or so, after which they likely will need some sort of correction, too.

Beyond granny glasses

For those who don't want to wear traditional bifocals or reading glasses, one available alternative is monovision contact lenses. They work by correcting one eye mainly for distance vision and the other mainly for close work, such as reading and computer work, so reading glasses are not needed. Not everyone can tolerate this approach, however, since it takes some getting used to.

Bifocal contact lenses include two powers in each lens, correcting for both distance and near vision, but many people find it difficult to adjust to them, ophthalmologists say. Newer models are under development.

Those who choose to undergo refractive surgery such as PRK (photorefractive keratectomy) or LASIK (laser-assisted in situ keratomileusis) -- procedures which reshape the cornea with a laser -- can also have one eye corrected mainly for distance and the other for close vision. (A trial period with monovision contacts is recommended first.)

On the horizon

An approach called surgical reversal of presbyopia (SRP) is under study by the Presby Corp. in Dallas. SRP involves placing four little pieces of inert plastic in a circular arrangement in the white part of the eye (the sclera), says Ronald A. Schachar, M.D., Ph.D., an ophthalmologist and surgeon who is Presby's CEO and president, and the developer of the patented technique.

This expands the underlying muscle, which can then better manipulate the lens, possibly allowing someone to see at multiple distances, thus reversing the effects of presbyopia, says Schachar. He hopes to get approval to begin clinical trials soon.

A California company, C & C Vision, is studying another technique, which replaces the hardened lens of presbyopic eyes with an artificial, more flexible lens implant that moves forward and backward, allowing the eye to see at different distances.

Within two years or so, depending on the results of clinical trials, these newer options could be widely available -- and could give reading glasses a run for their money.



RELATEDS AT WebMD:
Presbyopia
Laser vision correction with Antonio Vinals, M.D.

RELATED SITES:
American Academy of Ophthalmology
American Optometric Association


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