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During Eclipse, 'Your Eye Can Scorch'

solar eclipse

Aug. 9, 2017 -- The hype is true: Look directly at this month’s solar eclipse without good protection, and you can seriously damage your eyes. And not just for a little while.

Just ask Russell Van Gelder, MD, former president of the American Academy of Ophthalmology.

“I have one patient in his 60s who looked at the sun through a telescope when he was 9 years old and still has a central block in his vision,” says Van Gelder, chairman of the ophthalmology department at the University of Washington Medical School.

Your eyes wouldn't burst into flames. The impact of the sun’s rays is more like a branding iron. “The eye is actually a magnifier, and it is about 3 or 4 times stronger than most hand-held magnifying glasses,” Van Gelder says. And just as a magnifying glass can focus the energy of sunlight enough to set a piece of paper on fire, sunlight focused through the lens of your eye can scorch your retina with little or no warning.

Millions will turn their eyes toward the sky on Aug. 21 as a total solar eclipse crosses North America for the first time in nearly a century.

Doctors and astronomers are warning people to protect their eyes from the sun, which will be able to damage them until the moon covers it completely. Ahead of the eclipse, they’re trying to get the word out about proper protective glasses -- and warning consumers to beware of fakes.

“Even short periods gazing at the sun can cause damage,” says Van Gelder. “With the appropriate protection and knowing when it’s safe and not safe to look at the eclipse, you can still enjoy this pretty remarkable celestial event.”

First in More Than a Generation

A solar eclipse happens when the moon passes directly between the Earth and the sun, casting its shadow on our planet. A total solar eclipse happens when the moon completely obscures the sun. This month’s event will be the first total eclipse visible from North America since 1979, and the first to cross from coast to coast since 1918, according to NASA. 

“A total eclipse of the sun only covers less than a percent of the Earth’s surface, so most of the time it goes over the ocean or unpopulated areas or places that are on the opposite side of the world,” says Rick Fienberg, press officer for the American Astronomical Society. 

The last North American eclipse covered only a portion of the U.S. Northwest and western Canada. But this time, viewers in a 70-mile-wide swath from Oregon to South Carolina will see a total eclipse, while a partial eclipse will dim the entire continent. Excitement is building along the route, with thousands of events planned across the country.

Parties, Gatherings for the Big Event

In Nashville, the biggest city to fall into the path of complete shadow, members of the Barnard-Seyfert Astronomical Society have been in high demand to talk about the event. The club’s Theo Wellington says it’s not hosting one big event, but members will be at libraries, museums, and homes across the Nashville area where people will be watching.

“A lot of people are having big parties at their houses,” says Wellington, a former president of the 80-year-old club. “We’ve all got family, visitors, people we don’t remember from high school calling. I know I’ll have a houseful … and of course, this is repeated all the way up the path.”

If you’re in the path of a total eclipse, the only time you can view the sun with the naked eye is when the moon completely covers it, a period known as “totality.” At that point, the sun’s corona -- the glowing aura of gases that surround the star -- becomes visible.

But any other time, you should view the eclipse only through extremely dark “eclipse glasses” certified to block all but a tiny fraction of the sun’s rays -- or by using something like a pinhole projector, which you can make from a cereal box or sheets of paper. (NASA has instructions here.)

A Hole in the Retina

It’s a bad idea to look at the sun even when it’s down to a tiny sliver of its normal disk, says Van Gelder, the University of Washington ophthalmologist. The biggest danger is called solar retinopathy, when intense sunlight burns a hole in the retina -- the inner surface at the back of the eyeball where nerve cells pick up images.

“There are no pain fibers in the eye, so people don’t know they’re injuring their eye,” Van Gelder says. And based on the number of cases seen after a 1999 eclipse passed over southeastern England, “We could be looking at quite a few people, into the thousands, who develop solar retinopathy if appropriate precautions are not taken,” he says.

Fienberg says normal sunglasses block about half the light that strikes their lenses, but properly manufactured protective glasses used to view an eclipse will block all but a thousandth of 1% of that light. They’re required to meet an international standard, known as ISO 12312-2, and that number is marked on the glasses.

However, the American Astronomical Society recently warned that many vendors are selling glasses that don’t meet that standard -- even if they say they do. The organization is urging anyone looking for eclipse glasses to go through its own website for a list of sellers whose products have been certified to be safe.

“If you do a Google search for eclipse glasses, you’ll get dozens and dozens and dozens of sites that claim to be selling ISO-certified solar eclipse glasses, and many of them are bogus,” Fienberg says. “If the company you want to order from is not listed on the American Astronomical Society eclipse website, on our reputable vendors page, you should not buy from them.”

How to Watch Safely

Other eclipse-watching tips from the experts include:

  • Keep a close eye on children. “Most of the cases of solar retinopathy that I’ve seen have been kids,” Van Gelder says.
  • Don’t try to look through a telescope, binoculars, or a camera unless there's a special solar filter over the lens. Any device that magnifies an image also concentrates the light it collects, and that can overwhelm even the ultra-dark eclipse glasses, Fienberg says. “The fact is, you don’t need magnification to see the eclipse,” he says. “Most of us who have been to many total solar eclipses say the best view of the eclipse is just the naked-eye view.” Naked eyes, however, that are protected by the proper eclipse glasses.

Drive safely. Many motorists and pedestrians may be distracted during the eclipse, the Federal Highway Administration notes. And don’t try to drive while wearing your eclipse glasses, though that may seem obvious: “If you put these glasses on and try to walk around in them, you’ll feel like you’re blindfolded,” Van Gelder says.

WebMD Article Reviewed by Neha Pathak, MD

Sources

NASA.

American Academy of Ophthalmologists.

Russell Van Gelder, MD, University of Washington School of Medicine.

Rick Fienberg, American Astronomical Society.

Theo Wellington, Barnard-Seyfert Astronomical Society.

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