Doctors and patients cheered when two big government studies showed that certain formulas of common nutrients delayed the worsening of a blinding eye disease in certain people.
But certain was the operative word.
Now, a new study in the journal Ophthalmology finds that some top-selling brands of "eye vitamins" do not contain the proven formulas, and make overblown claims about protecting vision.
That doesn't surprise Julia Haller, ophthalmologist in chief of Wills Eye Hospital in Philadelphia.
"The multibillion-dollar supplement industry in this country is flourishing, but the claims are out of proportion to the scientific evidence," said Haller, who wasn't part of the new study. "If they're my patients, they go home with an information sheet on AREDS. And I warn them that [supplements] are a mostly unregulated area."
AREDS - the "age-related eye disease study" - was a clinical trial, published in 2001, that gave high doses of vitamins C, E, beta-carotene, zinc, and copper to patients with age-related macular degeneration, the leading cause of blindness in older adults.
The nutrients are believed to reduce oxidative stress that can injure cells in the eye.
Over six years, the AREDS formula delayed vision loss in those with intermediate or advanced macular degeneration - but not earlier-stage disease - by 25 percent.
Because beta-carotene supplementation may raise the risk of lung cancer in smokers, a follow-up study called AREDS2 replaced it with lutein and zeaxanthin. The results, out in 2013, showed that the modified formula also delayed the progression of macular degeneration.
Neither the original nor the modified formula warded off cataracts.
While these trials define a rather narrow role for eye vitamins, it matters because the most common form of age-related macular degeneration has no specific treatment.
"A 25 percent reduction is huge," Haller said. "That translates into hundreds of thousands of people not getting severe" vision loss as rapidly.
Bausch & Lomb holds the patent to both AREDS formulas; it also licenses Alcon Laboratories to use the formula in a product.
The new study - conducted by researchers at four medical centers including Penn State College of Medicine - found that numerous ocular supplements capitalize on the landmark AREDS studies in misleading ways.
Of 11 products the researchers reviewed, only four duplicated the proven formulas. Three were marketed by Bausch & Lomb: PreserVision Eye Vitamin AREDS Formula Tablets, PreserVision Eye Vitamin AREDS Formula Soft Gels, and PreserVision AREDS2 Formula. The fourth, ICAPS Eye Vitamin AREDS Formula, is made by Alcon Laboratories under license from Bausch & Lomb.
The seven other products - made by Bausch & Lomb, Alcon, and EyeScience Labs Inc. - contained lower doses of the nutrients. Four products added ingredients such as herbal extracts that weren't in the original formulas.
In all cases, promotional materials claimed the products "support," "protect," or "promote" vision and eye health. None explained that supplements have not been shown to prevent any eye diseases.
By law, dietary supplements need not demonstrate safety or effectiveness; they merely have to refrain from claiming to treat, prevent, or cure any disease.
Supplements are not necessarily risk-free - witness the beta-carotene link to lung cancer - or cheap. Popular eye vitamins cost about $20 a month.
"Our findings underscore the importance of ophthalmologists educating their patients" about eye vitamins, said author Jennifer J. Yong of Yale-New Haven Hospital-Waterbury Hospital in Connecticut.