How to watch Monday's solar eclipse safely—and what could happen if you don't

For the first time in nearly 40 years, tens of millions of people next week will be able to see a total solar eclipse visible in the contiguous United States—but the extraordinary event poses some (avoidable) risks.

According to NASA, all of North America will be able to view at least a partial solar eclipse on Aug. 21, and those in a narrow strip of land between Salem, Oregon, and Charleston, South Carolina, will be able to view "one of nature's most awe-inspiring sights—a total solar eclipse."

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But experts warn the event is not without its risks: Staring directly at the sun can cause eye damage, but its usual brightness typically makes it too uncomfortable for most people to stare long. According to the Washington Post, however, an eclipse presents a special situation because there's a point during phenomenon when the sun's visible light is so reduced that while it can still cause damage, it's not painful to directly observe. According to the Post, it takes only a minute and a half, depending on weather conditions, for the sun's light to permanently damage your eyes.

How to safely enjoy the eclipse

According to experts, people who want to view the eclipse should: 

1: Wear eclipse glasses. To safely watch the eclipse, experts stressed that people must wear very strong protective eye gear—your regular sunglasses aren't going to cut it. According to Rick Fienberg, an astronomer and press officer for the American Astronomical Society, real "solar viewers" are several thousand times stronger than everyday sunglasses. Ultimately, experts said, the only safe time to observe the natural phenomenon with the naked eye is during totality, when the moon completely blocks the moon—if any part of the sun remains uncovered, viewers must wear the appropriate eye protection to prevent damaging their eyes.

2: Seriously, wear eclipse glasses. If you try to observe the solar eclipse without the right eye protection, according to one optometrist, it would be "like a magnifying glass on a leaf when you were a kid." As Ralph Chou, professor emeritus of optometry and vision science at the University of Waterloo, put it, "That crescent of sun is glowing every bit as brightly as it would on a day when there isn't a solar eclipse. ... The difference is that instead of leaving a round burn on the back of the eye, it will leave a crescent-shaped burn at the back of the eye." And quick, surreptitious glances aren't safe either, Chou added. "Those quick little glances do add up, and they can, in fact, accumulate to the point where you do get damage at the back of the eye."

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3: Make sure you're using legitimate eclipse glasses. According to Feinberg, this is not the time to experiment with a pair of DIY eclipse glasses crafted with exposed film negatives, smoked glass, or the wrappers from your bag of potato chips or Pop-Tarts. And if you do purchase eclipse glasses, make sure they are legitimate. According to Fienberg, officials have been receiving consumer complaints about "what appear to be ordinary sunglasses being sold as solar viewers." Not sure where to start? NASA has a list of companies whose eclipse glasses have been demonstrated to meet international safety standards established by medical experts, NPR reports.

4: No glasses? Watch the eclipse 'indirectly.' Chou does have one recommendation for those who can't access a pair of eclipse glasses: Observe the eclipse indirectly. Chou said he used the method himself when he observed his first solar eclipse at just 12 years old, using a pinhole viewer to project the image to a flat surface that he could safely look at. But "indirect" does not mean you can safely view the eclipse through a telescope or camera lens, experts added—your eyes will be safe only if you are viewing the event through a filter that is specifically crafted to block harmful rays. In fact, according to the Washington Post, your camera may itself be damaged unless you use the proper filters and gear.

In case you need a catchy tune to help you remember all this advice, St. Luke's Health System made a music video revamping Bonnie Tyler's "Total Eclipse of the Heart" as "It's a Total Eclipse, I'll Be Smart." Here are the all the key pointers from staff at the system—including the resident therapy dog:

What happens if you do burn your eyes?

While researchers are not systematically tracking eclipse-related vision loss, experts say some eclipse-viewers inevitably will fail to take proper precautions and damage their eyes. "Unfortunately, I think it is probably true that during every solar eclipse, there's bound to be somebody who does get hurt," Chou said.  

According to the Post, those who experience eclipse-related vision damage may report blurry or spotted vision. Those who have more significant damage might lose the ability to look out of the center of their eyes entirely; they'll have only peripheral vision. And Chou said only about half of injured people will experience improvement over several months to a year—for the other half the vision loss is permanent.

The damage, however, isn't immediately apparent. According to Chou, the eye's light-sensitive cells typically keep functioning for several hours after injury. As a result, Chou said people often go home after viewing an eclipse thinking their eyes are fine only to wake up the next day with vision problems.

But ultimately, if safely enjoyed, the "eclipse is a cause for wonder, not fear," the Post reports. "If Earth didn't have a moon, and if relative sizes of the sun and moon weren't just right, we wouldn't experience eclipses at all. So marvel at it. Revel in it. Be glad that, of all the billions of planets in the universe, this is the one you get to call home" (Fritz, Washington Post, 6/30; Greenfieldboyce, "Shots," NPR, 8/1; Kaplan, Washington Post, 8/11; Wright, Boise State Public Radio, 8/15; NASA eclipse resources page, accessed 8/15).

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