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Fluid in eye cells may ‘boil’ if you watch eclipse without protection: expert

Millions of people in parts of Eastern and Atlantic Canada will be able to view the rare solar eclipse on April 8. But they should only look up if they’re wearing adequate eye protection, experts say.

Why is observing the eclipse more dangerous than looking at the sun on a normal day?

When people normally look at the sun, the intense brightness triggers pain that causes them to quickly look away before it can cause damage, said Dr. Philip Hooper, president of the Canadian Ophthalmological Society.

But as the moon begins to block the sun in the period leading up to the total eclipse, “there is significant light energy coming from the sun, but we don’t appreciate the pain.” And so you can stare at it long enough to do damage. “in the eyes,” said Hooper, who is also an associate professor of ophthalmology at Western University in London, Ontario.

How does looking at the sun damage our eyes?

When you look directly at the sun, intense visible light and infrared radiation are focused on the center of the retina at the back of the eye.

“It’s like taking a magnifying glass to the sun on a normal day and focusing that light on a piece of paper. It can get hot enough to burn the paper,” Hooper said.

The sun has the same effect, because your eye concentrates this energy in a small area of ​​the retina.

“The temperature of the cells in this area can actually get high enough that the fluid in the cells boils and permanently damages the cells,” he said.

This microscope image provided by the New York Eye and Ear Infirmary at Mount Sinai shows damage to the retina of a person who viewed the 2017 eclipse without adequate protection. She complained of a black spot in her vision and doctors discovered retinal damage matching the shape of the eclipse. (Mount Sinai via AP)

Can I just put on my sunglasses to watch the eclipse?

No, sunglasses don’t offer protection, Hooper said.

What if I stay inside and look out the window?

Again, no. Windows offers no protection.

Is it safe to watch through a phone camera?


“Eclipse or not, you should not look at the sun directly with the naked eye, or with a camera or telescope, without a (certified) solar filter. This can lead to irreversible eye damage,” says a safety video regarding the eclipse published online. by the Canadian Space Agency.

Pointing your phone’s camera directly at the eclipse can also have other consequences.

“Remember that your phone camera has lenses, just like glasses, and light comes from the sun as soon as you open the shutter,” said Elaina Hyde, director of the Observatory Allan I. Carswell of York University in Toronto.

“At the very least, you can expect to damage your camera. You won’t be able to see anything because your phone isn’t capable of handling that light.”

How to observe the eclipse safely?

You’ll need special glasses with filters designed for viewing eclipses, the Canadian Space Agency website says.

These glasses should have side protection so light rays cannot enter, Hooper said.

They must also have certified lenses, he added.

ISO 12312-2 certification must be printed on the glasses, which means that the glasses meet international safety standards.

When you wear glasses, you shouldn’t see anything unless you’re looking at the sun.

“No matter how bright you are exposed to in your indoor environment, if you shined a really bright light through them, you wouldn’t see anything. They’re totally black. That’s how dark they are,” he said. Hooper said.

Eclipse glasses should not be used if they are “scratched, punctured, torn, or otherwise damaged,” the American Astronomical Society says on its website, emphasizing that people should inspect their glasses before using them.

The company also says that children using the glasses during the eclipse should be supervised at all times.

Where can I get ISO 12312-2 certified glasses?

Free eclipse viewing glasses are available in many libraries, cities and school districts across Canada, according to the Royal Astronomical Society of Canada website.

The American Astronomical Society has a list of companies and retailers in Canada and the United States that sell certified solar eclipse glasses on its website.

Some companies that sell them in Quebec are listed on the Eclipse Quebec website.

What about welding goggles?

Welding goggles come in a variety of shades, designated by number, according to the Canadian Center for Occupational Health and Safety website.

The minimum darkness required to safely view the eclipse is shade 13, Hooper said.

“It’s much darker than the welding goggles typically used by welders. And they’re not widely available,” he said.

If I don’t have certified glasses, is there another option?

Another option for safe viewing is to make a spotlight so that you never look directly into the sun. It can be as simple as a piece of paper with a pinhole that shines sunlight onto the sidewalk, or a spotlight made from a box.

The Canadian Space Agency’s website offers simple instructions on how to make a projector using an empty cardboard box, a sheet of white paper, aluminum foil, a pin , adhesive tape and scissors.

For instructions, visit

-With files from Sonja Puzic

This report by The Canadian Press was first published March 29, 2024.

The Canadian Press’s health coverage is supported by a partnership with the Canadian Medical Association. CP is solely responsible for this content.

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