Eye wise: seeing into the future.

Eventually, your eyes wear out. First your focus starts to falter. Even middle-aged people who used to have 20/20 vision need glasses to read the fine print.

But that's just the beginning. Cataracts blur the vision of 20 percent of people in their 60s, more than 40 percent of people in their 70s, and nearly 70 percent of those in their 80s.

Worse yet, by age 75, more than one out of four people shows signs of damage to the retina Degeneration of the macula, the center of the retina, is the leading cause of irreversible blindness in the U.S.

But vision loss isn't inevitable. The right foods, vitamins, and exercise may keep your eyes younger as you age.

Spinach salad or Caesar? Grilled salmon or roast chicken? Nuts or chips? An apple or a doughnut?

It's no surprise that what you eat can inflate your waistline, clog your arteries, and raise your blood pressure. But few people think of their eyes as they scan a menu or pack a snack.

Yet a growing body of evidence suggests that certain vegetables, fruits, fish, nuts, and other foods can protect your vision, while certain fats and baked sweets like cakes, cookies, and pies may blur it. And some supplements may stave off eye damage while others are useless.

The catch is that vision rarely deteriorates in the blink of an eye. To keep seeing clearly, you've got to start early.

Cataracts

At first, it seems like you've got dirty glasses. Colors seem dimmer. Bright lights have a glare. By the time you have a ready-to-be-extracted, or "ripe," cataract, it's almost as though you're looking through a waterfall. (That's what the word "cataract" means.)

What causes the lens to become opaque in places? Researchers aren't sure, but they believe that fibers in the lens play a role.

"The lens continues to lay down new fibers throughout life," says Frederick Ferris III, director of clinical research at the National Eye Institute. "But it can't grow in size because it's stuck inside the eye, so the fibers become more densely packed."

That's one reason people lose the ability to see things that are near as they age, he explains. "The lens loses flexibility so it can't focus up close."

Proteins in the lens are also at fault. "Normally, molecules in the lens keep the proteins separate, in a pattern that allows light through," says Ferris. "But the balance that keeps the lens clear may tip in the direction of proteins clumping together."

The solution: surgery. Out goes the clouded lens; in goes a clear plastic replacement.

Doctors remove more than 1.5 million cataracts each year in the U.S., at a cost that accounts for more than 12 percent of the Medicare budget.

"Delaying cataracts by 10 years could reduce the number of extractions by half," says Julie Mares, a professor in the department of ophthalmology and visual sciences at the University of Wisconsin Medical School in Madison.

But how? Here's what we know so far.

* Antioxidant vitamins. "We have pretty consistent evidence that people who take multivitamins have lower rates of cataract," says Mares.

Researchers believe that oxidation promotes cataracts by damaging the proteins in the lens. "Oxidative stress is high in the eye due to the intense light exposure," explains Mares. And antioxidants seem to protect the lens in animal studies.

But the evidence in humans isn't airtight. In several studies, people who took multivitamins were less likely to get cataracts. (1,2) But in one study, the risk was lower only in people who took vitamin C, not other antioxidants. And the longer they took it, the better. (3)

"You don't seem to get the benefit until you've taken supplements for at least five years, and we see the greatest benefit in people who've taken them for at least 10 years," says Paul Jacques of the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University in Boston.

But that doesn't mean that more is better. While women who got 240 mg to 360 mg a day of vitamin C had the lowest risk, higher doses didn't cut the risk further.

"That's consistent with our observation that human eye tissues are saturated at intakes of 200 to 300 mg of vitamin C a day," says Jacques.

Still, researchers aren't convinced that vitamin C is a magic bullet. "It's too early to narrow it down to vitamin C," says Mares. "We don't have enough data."

One reason: so far, most evidence that vitamins of any kind keep cataracts at bay comes from studies of people who choose to take supplements on their own.

"We're not sure if people who take multivitamins also eat better and do more physical activity," says Mares, though studies try to account for those and other factors.

To get stronger evidence, researchers have to randomly assign people to take vitamins or a placebo and wait five or 10 years. So far, five out of six of those trials found no benefit from high doses of vitamins. (2)

For example, in the Age-Related Eye Disease Study (AREDS), which followed more than 4,600 people for more than seven years, cataracts were no less common in people who were given high daily doses of beta-carotene (15 mg, or 25,000 IU), vitamin C (500 mg), and vitamin E (400 IU) than in those who got a placebo. (4)

"But both groups were well-nourished," says Jacques. "Two-thirds of the controls were taking Centrum-like supplements provided by the investigators." Were the lower doses in an ordinary multi enough to protect their eyes?

Two trials in China suggest that a multivitamin might be enough for people who are undernourished. "In a nutritionally deprived region in China, multivitamins lowered the prevalence of cataract," says Mares. "A supplement containing 120 milligrams of vitamin C and molybdenum did not."

A clearer answer for Americans may come in a nine-year trial testing ordinary multivitamins against a placebo on 1,000 people in Italy, says Mares. "So far, the literature doesn't suggest that taking anything more than a regular multivitamin would be useful."

* Lutein. Lutein and its close cousin, zeaxanthin, are pigments found mostly in fruits and vegetables, especially leafy greens like spinach, collards, and kale. (The two are so close that when we say "lutein," we generally mean both.)

In studies that ask people what they're eating and wait to see who gets which disease, lutein seems to help ward off cataracts. "The data from observational studies on cataracts and lutein is quite consistent," says Mares.

In three large studies, people who got the most lutein from their food had a 20 to 50 percent lower risk of getting a cataract or having cataract surgery than people who got the least lutein. (5,6) But exactly how lutein might protect the lens is still fuzzy.

"Lutein and zeaxanthin absorb blue light," says Mares, "but as far as we know, only ultraviolet light is damaging to the lens." So it's too early to say that light at the blue end of the spectrum matters.

"Until we know more, we have to assume that lutein works as an antioxidant," says Jacques.

How much lutein is enough? In studies of more than 36,000 men and 77,000 women, researchers found the lowest risks of cataract surgery in those who consumed about six milligrams (6,000 micrograms) or more a day. "That's well within the range you can get in the diet," says Mares.

For example, men who ate broccoli or raw spinach more than twice a week were about 25 percent less likely to have cataract surgery than men who ate those vegetables less than once a month. (6) Men who ate cooked spinach at least twice a week had about half the risk of surgery, probably because there's more lutein in a typical serving of cooked than raw greens (see "Playing the Lutein").

Corn is rich in zeaxanthin, but it wasn't linked to a lower risk.

* Overweight. Most cataracts are either in the inner (nuclear) or outer (cortical) section of the lens. But a cataract at the back of the lens (posterior subcapsular) is the worst.

"Posterior subcapsular cataracts are the least common but the most important because they lead to surgery more frequently than other cataracts," explains Jacques.

Clouding in the back of the lens is most likely to blur vision because that's where light rays are focused into a narrow beam. They're the cataracts that typically cause glare and halos, and they're linked to your waistline.

"Individuals who are overweight tend to have a higher risk of posterior subcapsular cataracts." says Jacques. A supersized belly puts you in greatest jeopardy. Posterior cataracts are roughly twice as common in women with a waist larger than 35 inches than in women with a waist smaller than 31 inches. (7)

"People with diabetes are also more likely to get posterior subcapsular cataracts," says Jacques. What's the link? In both diabetes and obesity, "high blood sugar levels may damage the protein in that part of the lens."

Macular Degeneration

Think of your retina as the film in your (old-fashioned, non-digital) camera. Rods (which handle peripheral and night vision) and cones (responsible for color and sharp vision) convert the image into electrical impulses, which travel to your brain via the optic nerve.

The most sensitive part of the retina is the macula. There, millions of cones are tightly packed to create a high-solution image. It's the macula that can deteriorate with age.

"The cells in your retina--which are there from birth--work very hard," explains Ferris. "They're among the most metabolically active cells in the body."

And time takes its toll. "The cells accumulate debris over the years, and eventually it catches up with them and they stop functioning properly."

The macula decays in one of two ways. "In dry macular degeneration, cells essentially give up the ghost and die." Ferris explains. "In wet macular degeneration, the cells are sick and crying for help."

The body pitches in by building new blood vessels to nourish the cells. "But this call for blood vessels messes up the job," says Ferris, "because the blood vessels are abnormal and fragile. They can bleed and leak fluid and that causes rapid vision loss."

Doctors can treat the wet type by destroying the new blood vessels with lasers. There is no treatment for the dry type, which accounts for 90 percent of cases. That's why scientists are so eager to prevent or slow the disease. Some of what they're looking at:

* Zinc & antioxidant vitamins. You win some, you lose some. High doses of antioxidant vitamins (C, E, and beta-carotene) didn't prevent cataracts in the Age-Related Eye Disease Study, but they did slow macular degeneration (see "Seeing AREDS," p. 6). (8) So did a high dose (80 mg a day) of zinc.

"Either antioxidants or zinc made a difference, but the combination worked better than either one alone," says Ferris. Taking both supplements cut the odds that macular degeneration got worse by about 25 percent, but only in people who were at high risk for advanced macular degeneration when the study began.

That's no small potatoes. An estimated eight million people in the U.S. fall into that group.

"If they all took the AREDS supplements, it would prevent more than 300,000 cases of advanced macular degeneration during the next five years," says Ferris. "But that leaves over a million cases still in progress, so we have a long way to go."

How zinc might protect the retina isn't clear, but researchers have some clues. "The epithelial cells that lie under the retina and nourish it have the highest concentration of zinc of any tissue of the body, with the possible exception of the prostate gland," explains Ferris. "And zinc is tied up in many enzymes that may be important in the eye," a number of which act as antioxidants.

But some experts worry that healthy people will start taking high doses of antioxidants and zinc to prevent the disease.

"When I talk to people with macular degeneration, they proudly announce that they've told their sons and daughters to take these supplements," says Mares. "So some people may be taking boatloads of antioxidants and zinc for decades."

She worries that high doses of antioxidants could interfere with statin drugs like Lipitor and Zocor, and that beta-carotene could raise the risk of lung cancer in smokers.

What's more, she adds, "the long-term use of zinc has been linked with prostate cancer, and AREDS found more urinary tract problems in people who took zinc."

Most of those problems were benign prostatic hypertrophy (enlarged prostate) and urinary tract infections, with only a few prostate cancers--and there were no more cancers in the zinc takers than in placebo takers, says Ferris. So far, only one study has found a higher risk of advanced prostate cancer in people who took zinc for at least 10 years.

Until we know more, says Mares, only people with intermediate or advanced macular degeneration should take high-dose supplements. "We don't know if they're effective in people in the early stages of the disease," she says. (AREDS wasn't large enough to tell.) "And it's unknown whether half of the AREDS doses would be equally effective."

* Lutein. It's no surprise that lutein is a prime candidate for chief macula defender. "Lutein is deposited in the retina and concentrated in the macula," says Ferris. In contrast, beta-carotene is nowhere to be found.

And researchers have theories to explain why lutein may help. "Lutein absorbs blue light and it's in front of the ceils that develop macular degeneration, so it may lessen the potential for light to cause oxidative or photochemical damage," suggests Mares. "Lutein is also found in the membranes of cells that die in macular degeneration, so it may have an antioxidant role there."

Studies show that taking a lutein supplement raises lutein levels in the macula. But so far, they haven't consistently found a lower risk of macular degeneration in people who happen to eat more lutein-rich foods.

"Some studies show a link and some don't," says Mares, possibly because many studies have looked at well-nourished populations like nurses, most of whom get sufficient lutein.

The answer may come in a large trial that the National Eye Institute is now planning. "We're still working on the dose," says Ferris, "but it will probably be between six and 15 mg a day."

It's easier to get there with leafy greens than with most supplements. Six milligrams is 24 times more than the 250 micrograms (0.25 mg) you would get in a multivitamin like Centrum Silver.

"Lutein is expensive," says Jacques, "so most supplements have incredibly low amounts compared to what you would get in the diet."

* Fish, nuts, sweets. The National Eye Institute's lutein trial will also test DHA (docosahexaenoic acid), one of the two major omega-3 fish oils.

"In AREDS, people who ate fish at least twice a week had a 50 percent lower risk of advanced macular degeneration compared to people who ate no fish," says Ferris.

Results from other studies are similar. For example, when Harvard researchers tracked more than 42,000 women and 29,000 men for 10 to 12 years, those who ate fish one to four times a week had a 23 percent lower risk of macular degeneration than those who ate fish three times a month or less. (9) People who ate fish (mostly canned tuna) more than four times a week had a 35 percent lower risk.

Why single out DHA? "We know that DHA is a very important lipid in rods and cones," says Ferris. "It's also important in the brain, and the eye is really an outcropping of the brain."

Only one other food seemed to keep macular degeneration from getting worse. Harvard researchers found that patients who ate nuts at least once a week had a 40 percent lower risk of advanced disease than those who never ate them.

In contrast, those who ate baked sweets--like store-bought cakes, cookies, pies--and potato chips at least two or three times a day had more than double the risk of people who ate those foods only once every two weeks or so. (10)

Trans fats in the sweets and chips may be to blame, says Harvard researcher Johanna seddon. But since anyone with eyes also has a heart, they should already be avoiding trans-heavy foods.

* Obesity. Can the battle of the bulge turn into a battle for your eyesight? Only a few studies have looked.

Researchers who studied more than 21,000 men in the Physicians Health Study found that obese men had more than double the risk of macular degeneration of men of normal weight. (11)

How fat affects the eyes isn't clear. "It could be an increase in inflammation or an increase in oxidative stress," explains Debra Schaumberg, director of ophthalmic epidemiology at Brigham and Women's Hospital in Boston. Her study found a smaller elevated risk in people who were leaner than in people of normal weight, "but we've had a hard time coming up with a plausible explanation for that."

Extra pounds--especially around the waist--also seem to speed up damage to the macula. In a study of roughly 260 people who already had early or intermediate macular degeneration, the risk of progressing to advanced disease was double in those who were overweight or obese. (12)

Physical activity appeared to slow the disease's progress, but the study wasn't large enough to say for sure.

Eye Opener

As scientists try to nail down the foods or pills that can protect your eyes, don't forget to bring your blinkers in for a check-up every once in a while.

"Of the four leading causes of blindness--cataracts, diabetic retinopathy, glaucoma, and macular degeneration--all but cataracts can progress without your knowing it," warns Ferris. "The sad part is that by the time you can tell you have them, it's often too late to make a difference."

Anyone older than 60 should have a dilated eye exam. Just getting a new prescription for glasses isn't enough. "You can have good vision and these processes could be rampant," Ferris explains. "Only by looking at dilated eyes can the doctor tell."

(1) Arch. Ophthalmol. 118: 1556, 2000.

(2) Nutr. Rev. 62: 28, 2004.

(3) Arch. Ophthalmol. 119: 1009, 2001.

(4) Arch. Ophthalmol. 119: 1439, 2001.

(5) Amer. J. Epidemiol. 149: 810, 1999.

(6) Amer. J. Clin. Nutr. 70: 509, 517, 1999.

(7) Amer. J. Clin. Nutr. 78: 400, 2003.

(8) Arch. Ophthalmol. 119:1417, 2001.

(9) Amer. J. Clin. Nutr. 73: 209, 2001.

(10) Arch. Ophthalmol 121:1728, 2003.

(11) Arch. Ophthalmol. 119: 1259, 2001.

(12) Arch. Ophthalmol. 121: 785, 2003.

Got a Cataract?

These symptoms of a cataract may also signal other eye problems. Check with your doctor to find out.

* Cloudy or blurry vision

* Colors seem faded

* Glare (headlights, lamps, or sunlight may appear too bright or a halo may appear around lights)

* Poor night vision

* Double vision or multiple images in one eye (this symptom may clear as the cataract gets larger)

* Frequent prescription changes in your eyeglasses or contact lenses

Playing the Lutein

If you're looking for lutein-rich vegetables and fruit, here's where to start.

Vegetables                     Lutein +
and Fruits                    Zeaxanthin
(1/2 cup cooked             (milligrams)
vegetable, unless noted)

Kale                               11.9
Spinach                            10.2
Swiss chard                         9.6
Collard greens                      7.3
Spinach (1 cup raw)                 3.7
Peas, frozen                        1.9
Broccoli                            1.2
Romaine lettuce (1 cup raw)         1.1
Brussels sprouts                    1.0
Zucchini                            1.0
Asparagus                           0.7
Corn                                0.6
Green beans                         0.4
Iceberg lettuce (1 cup raw)         0.2
Nectarine (1)                       0.2
Oranqe (1)                          0.2

Whose macula is at risk?

Macular degeneration causes no pain. Age is by far the greatest risk factor. Others include:

* Caucasian race

* Family history

* Female gender

* Obesity

* Smoking

Seeing AREDS

Do you have macular degeneration that's either intermediate or advanced (not early)?

If so, talk to your doctor about whether to take the high-dose daily supplements used in AREDS--the Age-Related Eye Disease Study: vitamin C (500 mg), vitamin E (400 IU), beta-carotene (15 mg, or 25,000 IU), zinc (80 mg), and copper (2 mg).

Make sure you take zinc oxide, because zinc gluconate could lead to higher blood levels of zinc. Researchers added the copper because high doses of zinc may interfere with copper absorption.

At high doses, zinc may raise the risk of prostate cancer, lower HDL ("good") cholesterol, and impair immunity. High doses of beta-carotene may increase the risk of lung cancer in smokers. But if your vision is in danger, the benefits to your eyes may outweigh those potential risks.

The Bottom Line

To lower your risk of cataracts and/or macular degeneration:

* Don't smoke.

* Eat leafy green vegetables like spinach and broccoli at least twice a week.

* Eat fish at least once a week.

* Take a multivitamin for insurance.

* Lose excess weight.

* Snack on fruits, vegetables, or nuts instead of cookies, cakes, pies, or chips.

* Have a doctor check your eyes after dilating them at least once in your 20s, twice in your 30s, every two to four years between ages 40 and 64, and every one or two years at age 65 or older.

* If you have intermediate or advanced macular degeneration, talk to your doctor about taking antioxidants or zinc.

RELATED ARTICLE: Eye candy?

Most eye supplements contain some mix of vitamins, minerals, and/or lutein. Two other ingredients that frequently appear:

* Bilberry. The bilberry is the fruit of a shrub that's related to the North American blueberry. The "evidence" that it can help protect against cataracts and macular degeneration comes from two Italian studies--published in obscure journals 15 years ago--that were never followed up.

In one, the progression of cataracts was halted in 24 of 25 people taking bilberry extract (360 mg) and vitamin E (200 IU) every day for four months. But that was a statistical tie with the placebo, which halted the progression in 19 of the 25 people given look-alike but inactive pills.

In the second study, bilberry improved the "macular recovery time" of healthy people and of diabetics without eye disease. That's a measure of how fast the macula returns to normal after being exposed to a bright light. It's not clear how--or if---macular recovery time is related to macular degeneration.

* Taurine. Animals made deficient in the amino acid taurine suffer damage to their retinas, according to John Barry Lombardini of Texas Tech University in Lubbock, Texas, possibly because taurine can function as an antioxidant. In the only human study, conducted in Mexico, three years of taurine plus vitamin E and the high blood pressure medicine Cardizem every day seemed to slow the loss of vision in people with retinitis pigmentosa.

But there's no good evidence that taking taurine can prevent cataracts or macular degeneration.

--David Schardt