New clear options for cataract sufferers
By the faculty of Harvard Medical School for The Harvard Medical School Adviser

Q: I am having cataract surgery next month and have heard about some new types of replacement lenses. Can you tell me which ones could best improve my vision?

A: Each of our eyes comes with a natural lens. It's important for these lenses to be clear because they focus outside light into the back of the eye, making it possible for us to see. Young peoples' lenses are usually crystal clear. But by the time we're in our 60s or 70s, decades of exposure to light can "cook" tiny proteins inside the lenses. This makes them cloud up like egg whites in a frying pan.

A clouded lens is called a "cataract." The name comes from the Greek word for "something rushing down." Naturalists sometimes refer to waterfalls as cataracts, but doctors use the term to suggest a curtain falling down on clear vision. A cataract can make it hard to see things well. It blurs details, dulls colors and interferes with night vision.

Cataract surgery involves removing a clouded natural lens and replacing it with a plastic one. Afterwards, patients may be less dependent on their glasses. While the operation itself (see illustration) hasn't changed much in recent years, the plastic lenses have. Today, patients face lots of choices.

Basically, there are three different kinds of replacement lenses. They are monofocal lenses, accommodating lenses and multifocal lenses. Each has its advantages and disadvantages.

Think of monofocal lenses as the basic model: no frills, but reliable and with a long track record. They are good for focusing on things at one distance. Most people will still need glasses either for reading or for seeing things far away after receiving monofocal lenses. A big plus for monofocal lenses is their relatively low cost. They are the only variety fully covered by Medicare.

Accommodating lenses show us that it's good to be flexible -- even in our eyes. As we look at our immediate surroundings, tiny muscles tug on our lenses, reshaping them ever so slightly. This allows us to shift easily between seeing things close up and far away. Eye doctors describe this ability as "accommodation."

With age, the lenses get stiff -- or less accommodating. Shifting focus becomes a problem. That's where the flexible Crystalens lens comes in. Approved by the Food and Drug Administration in 2003, the Crystalens lens mimics the action of younger eyes. Hinges on the sides of these lenses let the tiny eye muscles reposition them.

The Crystalens lenses help patients see clearly from medium to long distances. But close-up vision is not as reliable. Eye exercises can improve near vision, but about half of patients who received these lenses wind up needing glasses for reading and other close-up work.

Cost is also an issue. Many patients must shoulder the burden because Medicare won't fully cover Crystalens implants, which run about $2,500 more per eye than monofocal lenses. And most people get both lenses replaced, so the bill usually totals $5,000.

Multifocal lenses are like those used in bifocal or progressive glasses. Different parts focus on varying distances. But unlike glasses, the sections of multifocal lenses are arranged in concentric circles, like ripples in a pond, rather than from top to bottom. Amazingly, the brain and the eye figure out which part of the lens to use. There are two new brands of multifocal lenses on the market: Restor and Rezoom. The Restor lenses provide good near and far vision. However, people sometimes have problems with the middle range. The Rezoom lenses provide good vision for all three distances but are slightly less effective than the Restor lenses for reading. Their cost is comparable to the Crystalens implants.

The major drawback of multifocal lenses is that they sometimes worsen night vision. Tiny ridges in the lenses can distort bright light (as from oncoming headlights), so there's more glare and a halo effect. The Crystalens is free of these problems.

Some eye conditions make the accommodating and multifocal lenses a poor choice. If you have severe macular degeneration, glaucoma or diabetic retinopathy, monofocal lenses might be your best bet. Also, seriously nearsighted or farsighted people with astigmatism should avoid the new lenses.

The biggest source of dissatisfaction with the new lenses involves expectations, not eyes. Patients who expect perfect vision and a guarantee that they'll never have to wear glasses again are setting themselves up for disappointment.

It's nice to have so many options, but it can be confusing. Talk with your doctor to find out which lens should be your clear choice.

Copyright 2007 the President and Fellows of Harvard College. Developed by Harvard Health Publications (www.health.harvard.edu). Distributed by UFS. Submit questions to harvard_ adviser@hms.harvard. edu.