"This for the first time scientifically proves you have to have the impact from an object such as a bottle rocket to cause serious eye injuries," said Stefan Duma, who led the new work and calls himself a "big fan of fireworks."

There are more than 2,000 eye injuries from fireworks every year in the U.S., most occurring during the July 4th celebrations, but the exact mechanism behind them had escaped researchers until now.

Some argue it takes flying shrapnel to make eyes bleed or rupture, while others say pressure waves from the explosion itself are enough - in which case safety goggles might not offer adequate protection for those lighting firecrackers on Wednesday.

Duma's results, published Tuesday in the Journal of the American Medical Association, help settle that debate. "If you remove the projectile, you dramatically reduce the risk," he told Reuters Health.

For the study, his team used human eyes from an "eye bank" in North Carolina. "We put instrumentation into the eye," said Duma, who heads the Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences in Blacksburg, Virginia, and has spent two decades developing techniques to measure eye injuries. "Then we detonate charges at various distances from the eye."

Even at less than three inches, the researchers found, the damage to the eye was limited to surface scratches - called corneal abrasions - which usually heal on their own. The scratches got bigger the closer to the eye the explosion took place, and high-speed videos showed they were caused by unspent gunpowder flung onto the eyeball by the blast.

Dr. Terrence O'Brien, from the Bascom Palmer Eye Institute at the University of Miami, said he has seen eye injuries from fireworks ranging from minor abrasions to complete loss of an eye. "Of the 2,000 injuries every Fourth of July, the vast majority are in young adults and children," O'Brien told Reuters Health. "It's ironic that while celebrating our independence they lose their visual independence due to sight-threatening injuries."

He welcomes the new results, adding that they should help guide policy decisions on fireworks. Still, he pointed out that the study has some significant limitations, including that it was done in dead tissue. "We have to understand, this is a somewhat contrived experiment," he cautioned. "In the real world, it's not as controlled as this."

For instance, although Duma and his colleagues used charges similar to what is found in commercial firecrackers, a lot of real-life injuries are from homemade fireworks, which may be more powerful, O'Brien said.

"The message is, certainly we don't want to ground fireworks, but they should be carried out by professionals," O'Brien said.

For those who prefer the hands-on approach, added Duma, who has his own remote-controlled launchers ready, "first and foremost you have to have parental supervision. If possible having safety glasses would be the best thing. It's important to have kids wearing these from a very young age."

SOURCE: bit.ly/MvXYT6 Journal of the American Medical Association, online July 3, 2012.

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