Can Watching a Solar Eclipse Really Make You Go Blind?

How to safely view and photograph this astronomical phenomenon

Elizabeth Agnvall,

AARP

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En español

Published March 26, 2024

A woman holding a pair of solar eclipse glasses up toward her face

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Millions of people in North America will have a rare opportunity on April 8 to witness a total solar eclipse, which will pass over parts of the United States, Mexico and Canada. This phenomenon happens when the moon moves between Earth and the sun, completely blocking the face of the sun. As the moon’s shadow falls on Earth, the day will briefly darken into twilight.

An estimated 31 million people live in the “path of totality,” the narrow strip that will experience a total solar eclipse. NASA estimates 99 percent of people in the United States will be able to see a partial or total eclipse, depending on where they live.

Although this is an exciting astrological occurrence, it’s important to understand how to safely watch a solar eclipse without putting your vision at risk.

Can looking directly at a solar eclipse damage your eyes?

Yes. Staring directly at the sun without the right eye protection for even a short time can permanently damage your retina, the layer of tissue in the back of your eye that converts light to electrical signals for the brain. Usually, we naturally avoid looking directly at the sun because it bothers our eyes, but during a partial solar eclipse that natural aversion lessens because the sun is darkened.

Avoid the temptation to take a peek even during a partial eclipse, when the risk of retina damage remains high. The only time it’s safe to look directly at the sun, according to NASA, is during the brief phase of a total solar eclipse when the face of the sun is completely blocked by the moon.

How does damage to the eye happen?

We see by absorbing light that passes through the pupil to the retina in the back of the eye. Light-sensitive rods and cones in the retina signal to the brain what we are seeing. If we look directly at the sun, the powerful rays go through the eye to the retina. “The intense exposure triggers a series of complex chemical reactions that damage the light-sensitive rod and cone cells that help us see,” says Amita Vadada, M.D., an ophthalmologist with AdvantageCare Physicians in New York. “Burning the retina can lead to permanent central vision loss.”

Why is it dangerous?

During a partial solar eclipse, the sky becomes darker, as if it were dawn or dusk. Because the light of the sun is partially covered, the pupils dilate. When our pupils are open, more light can travel to the retina, causing even more damage. Because an eclipse is such a rare phenomenon, people are tempted to look, which is dangerous for the eyes. “I think when a solar eclipse happens, it’s so exciting, so people tend to just stare at it,” Vadada says.

How long does it take for eye damage to happen?

Looking at the sun directly, even during a partial eclipse, can cause permanent eye damage in less than a minute, according to Vadada, who is also a spokesperson for the American Academy of Ophthalmology.

How can you protect your eyes but still see the eclipse?

There’s only one safe way to look directly at a partial solar eclipse and that’s through special solar filters. These filters are used in eclipse glasses or handheld solar viewers and must meet a worldwide standard, ISO 12312-2. An eclipse can also be safely viewed indirectly by using a homemade box pinhole projector..

How do these special solar glasses protect the eyes?

Solar glasses work like extraordinarily dark sunglasses, but instead of reducing glare from the sun, they protect the eyes from damaging rays.

The lenses of solar glasses are dark and often have a metallic coating to improve reflectivity. Whereas sunglasses protect from UV light, the solar glasses also protect from infrared light from the sun.

“Solar filter glasses or solar filter viewers are extremely dark – not just across the visible, but also across ultraviolet and infrared,” says Rick Fienberg, project manager of the American Astronomical Society’s solar eclipse task force.

Filters that provide safe, comfortable views of the sun generally transmit between 1 part in 100,000 (0.001 percent) and 1 part in 2 million (0.00005 percent) of its visible light, according to the AAS.

Your regular sunglasses do not block enough light to protect your eyes.

How can you make sure you have the right glasses?

Unfortunately, there have been scams involving companies selling fake or counterfeit glasses that won’t protect your eyes. The AAS has a web page with a list of safe solar viewers and filters that they have verified and tested.

Fienberg says you can test your glasses by looking through them but not at the sun. If you can see anything, they aren’t dark enough.

Can you look at a total solar eclipse with the naked eye without causing damage?

If you are in an area with a total solar eclipse, you can look directly at the blocked sun but only during the time the sun is completely blocked. That path is about 115 miles wide. Within that path, the closer you are to the center of it, the longer the eclipse lasts. In Southwest Texas, for example, it will last just under 4½ minutes. The further you get from the center of the path the less time the sun will spend in what astronomers call totality.

During that phase, when the sun is completely hidden by the moon, the brightness is about the same as a full moon, says Fienberg, who has a doctorate in astronomy. In fact, if you are wearing solar glasses during totality, you won’t be able to see it.

“You are able to see the sun’s very hot, very tenuous, very rarefied outer atmosphere called the corona,” he says. “If you were to keep your eclipse viewers on during totality, you would literally see nothing, because it’s so much fainter than the bright sun’s face.”

As soon as the sun peeks out again, he says, you immediately need to put on your glasses because it’s no longer safe to look at it directly.

Can you take photos of a total solar eclipse?

To take a photo of a partial solar eclipse, you need to have a special filter on your smartphone or camera. If you look through a camera lens without solar filters, the rays can be amplified and burn your eyes. A partial eclipse can also damage the sensor in a camera or your smartphone camera.

Fienberg said you can either get special filters or cut the film from solar glasses and tape it over your cellphone. If you are careful, you then can look at the smartphone screen to take a picture, but he says this can still be dangerous because it’s tempting to peek around the phone at the partial eclipse.

Do not use unfiltered cameras or binoculars, even while wearing solar glasses, Fienberg warns.

“You mustn’t look through any kind of optics while wearing eclipse glasses because whether it’s a telescope, binoculars or a telephoto lens, it’s going to concentrate way too much light right onto that filter and melt it,” he says. “I’ve tested it. It doesn’t take more than a couple of seconds.”

Take in the magic

Fienberg, who has seen 14 total solar eclipses and will view this one from a cruise ship off Mazatlán, Mexico, with other eclipse enthusiasts, says this rare sight is not to be missed.

“It’s really something that everybody should experience, just like I would say everybody should have the good fortune to fall in love someday.”

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Elizabeth Agnvall is the health and healthy living editor at AARP.org. She has worked as editor of Staying Sharp, AARP’s brain health platform and as a health editor at the AARP Bulletin. She also wrote for the Washington Post health section.