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Why the solar eclipse can damage your eyes and how to see it safely, according to a doctor

Almost everyone in the U.S. will be able to see a partial or total solar eclipse from where they live on April 8. Eye safety will be key.
/ Source: TODAY

Happy solar eclipse day! It's here, Monday, April 8, when our tiny corner of the universe will align and put on a spectacular show that can also be dangerous for your eyes — so you should know how to see it safely.

Live updates: Following along our total solar eclipse live blog

The moon will move between the Earth and the sun, casting its shadow on our planet and turning day into night in some places. The path of totality, where people will see the moon totally block the sun, will pass over Mexico, the U.S. and Canada.

Totality in the U.S. starts in Texas at around 1:40 p.m. Central/2:40 p.m. Eastern and continues to race northeast along the path until about 3:34 p.m. Eastern in Maine, lasting for about four minutes in each location, according to NASA.

More than 31 million people live in the path of totality and will be able to see the moon block out the sun during the solar eclipse on April 8, NASA says.
More than 31 million people live in the path of totality and will be able to see the moon block out the sun during the solar eclipse on April 8, NASA says.Courtesy NASA Scientific Visualization Studio

It’s much wider and much more populated than the path of the 2017 solar eclipse, so many more Americans will see it, NASA notes.

In all, 99% of people in the U.S. will be able to witness a partial or total eclipse from where they live, the agency says.

Some schools are closing to keep children safe amid worries about eye safety and increased traffic. Some communities in the path of totality have declared a state of emergency amid an influx of crowds.

Is the solar eclipse harmful for eyes?

It can be if you don't have special glasses or viewers. We’ll all be tempted to gaze up at the sky, but many people don’t realize they can get hurt by staring directly at the sun without the proper protection, says Dr. Russell N. Van Gelder, professor of ophthalmology at the University of Washington School of Medicine.

“The danger is real for permanent vision loss,” Van Gelder, a clinical spokesperson for the American Academy of Ophthalmology, told ahead of the 2017 eclipse.

“It’s a big deal for us. We don’t have a lot of public health issues in ophthalmology where we’re really worried about things that threaten the eye health of the population."

Even a few seconds of viewing the sun during an eclipse can burn the macula, which is part of the retina, "the light-sensitive tissue at the back of the eye that enables people to read and recognize faces," eye doctors warned in JAMA on March 8.

Why your eyes are in danger

You may remember taking a magnifying glass outside as a child on a sunny day and burning a hole in a leaf or starting a small fire. It takes just a few seconds for the smoke to start.

Your eye is basically a very powerful magnifying glass, Van Gelder says. If you stare at the sun, you’re focusing all the energy of that light onto your retina and essentially burning a hole. You won’t feel it because the retina doesn’t have any pain fibers, but the damage can happen after a few seconds.

We all have a natural aversion to staring at very bright lights, but we also have the ability to overcome it.

“The worry in the eclipse is that people are so interested to see one of the great astronomic spectacles that they will suppress their inner drive to look away from the very bright light,” Van Gelder says.

How vision could be damaged

The damage is known as solar retinopathy. That can include blind spots, distortions or loss of contrast in your central vision, which is what you use to read, drive and work on the computer.

There have been reports of people becoming legally blind in at least one eye after watching eclipses, Van Gelder says. profiled a woman who watched the 2017 solar eclipse with faulty eclipse glasses for about 30 seconds and developed a blind spot in the middle of her left eye.

Nia Payne, then 26, was diagnosed with solar retinopathy. Doctors noticed her blind spot was crescent-shaped, likely reflecting the shape of the sun she saw in New York City, which experienced a partial solar eclipse.

Studies show about one-quarter of patients who develop solar retinopathy suffer permanent damage, Van Gelder notes.

Young adults may be "especially susceptible" to eye injury because they have larger pupils and may be less aware of the dangers of looking at the eclipse with improper eyewear, researchers wrote in JAMA Ophthalmology.

Is it OK to look at the eclipse while wearing sunglasses?

No, regular sunglasses will “absolutely not” defend your vision from the sun’s powerful rays, Van Gelder warns. Even the darkest sunglasses do not reduce the amount of light hitting the back of your eyes by that much.

“They’re not an acceptable means for protecting your retina” if you stare directly at the sun, he says.

Clouds also don't provide protection.

How to see the solar eclipse safely

The only safe way to view the solar eclipse is with special glasses that have filters designed to block the sunlight from getting to your eyes, the experts say.

You may be tempted to look directly at the eclipse when it's total, meaning the sun is completely blocked by the moon, but it's still not safe, according to JAMA Ophthalmology. That's because the total eclipse lasts only one to three minutes depending on your location, and as the moon moves, the sun will reappear, which can lead to permanent damage even if you only see it for a few seconds.

“My strong, strong advice is take the two minutes to order the glasses for yourself and your family and then enjoy the eclipse without worrying that you’re going to blind yourself by looking at it,” Van Gelder says.

What glasses do you need for an eclipse?

You need glasses or hand-held solar viewers with special solar filters that meet a specific standard known as ISO 12312-2, according to the American Academy of Ophthalmology.

Using them may mean a million-fold decrease in the amount of light getting into the eye, Van Gelder says.

“These glasses basically turn day to night,” he notes.

You can buy the glasses online — the cardboard-frame versions cost just a few dollars — but check the American Astronomical Society’s list of reputable vendors first. The group also has some warnings about counterfeit and fake eclipse glasses.

American Paper Optics, which has become a leading supplier of eclipse glasses, expects to sell 75 million pairs this year.

“You want to make sure that your glasses were tested by a U.S lab and produced in the U.S.,” the Tennessee company's president and CEO John Jerit told NBC News. “I’m incredibly concerned [about counterfeits] because this is such an important event, and your eyes are too important.”

Wear the glasses any time you want to look at the sun, even if there’s only a small sliver of the star peeking behind the moon in a partial eclipse. That little sliver is still as bright and damaging as looking at direct sunlight, Van Gelder says.

If you wear regular glasses, put the eclipse glasses on top of them, NBC News medical correspondent Dr. John Torres advised.

Always keep a close eye on children using eclipse glasses to make sure they're wearing them before looking towards the sun and until they look away from it, the American Academy of Pediatrics advises.

How to spot fake or unsafe eclipse glasses

The lenses in genuine glasses are reflective — the front is silver — and have curved left and right edges. Counterfeit glasses have black lenses on both sides and lack that curved shape.

If everything looks legit, try the indoor test first: Put the eclipse glasses on inside your home and look around.

"You shouldn’t be able to see anything through them, except perhaps very bright lights, which should appear very faint through the glasses," according to the American Astronomical Society.

"If you can see anything else, such as household furnishings or pictures on the wall, your glasses aren’t dark enough for solar viewing."

If the glasses pass that test, try them outdoors on a sunny day — you still shouldn’t see anything through them, except the sun’s reflection off shiny surfaces, the organization noted.

Can I use my old eclipse glasses?

Yes, if you bought glasses or solar viewers that met the ISO 12312-2 standard for the 2017 solar eclipse, you can use them again if they're still in good condition, says Susanna Kohler, Ph.D., communications manager for the American Astronomical Society.

"You should inspect your glasses before using them, checking to make sure that they aren’t scratched, torn or coming detached from the frame," Kohler tells "If they aren’t damaged, you’re good to go — the filter will still be safe."

You may reuse glasses that meet the standard and are in good condition indefinitely, the American Astronomical Society noted.

How to make an eclipse viewer at home

If you don't have the special glasses, a pinhole camera is a safe way to watch the solar eclipse indirectly.

NASA's Jet Propulsion Laboratory and The Planetary Society have the instructions. You'll need:

  • Two pieces of white card stock paper (or paper plates)
  • Aluminum foil
  • Tape
  • Pin, paperclip or pencil

Cut a small hole in the middle of one of the pieces of paper, then tape a piece of aluminum foil over the hole. Use the pin, paperclip or pencil to poke a hole in the aluminum foil.

Stand with your back to the sun so you can see the shadow of your head and shoulders. Put the other piece of paper on the ground and hold the piece with the aluminum foil above it. You'll be able to view the projected image of the sun on the paper below and see it change shape as the moon blocks it during the eclipse.

How do I know if I damaged my eyes looking at the eclipse?

The American Academy of Ophthalmology says symptoms of solar retinopathy usually show up within hours of sun gazing. They include:

  • Blurry vision
  • A central blind spot in one or both eyes
  • Deficiency in color vision
  • Distorted vision where objects seem warped or smaller than they really are
  • Headache

People who experience vision problems after viewing a solar eclipse should promptly visit an ophthalmologist, eye doctors warn in JAMA. There's no definitive treatment, but people can sometimes partially recover their vision, they note.