Why and how to protect your eyes during the eclipse

Whether partial or total, a solar eclipse is a rare and spectacular event to experience, provided that certain safety instructions are observed.

Why is it necessary to wear special sunglasses during an eclipse?

If we look directly at the Sun on an ordinary day, the pain caused by the glare quickly forces us to look away. But when sunlight is partially blocked during an eclipse, infrared rays can cause damage before pain forces us to close our eyelids. And since the point of an eclipse is precisely to look directly at the Sun, wearing protective glasses becomes essential during the partial phases (before and after the total eclipse, if you are in the zone of totality).

What damage can be done to eyes that are not well protected?

Light is first filtered by the lens of the eye, which acts as a magnifying lens, and focuses on the retina. “In this case, it’s like focusing sunlight through a magnifying glass on the retina,” says Dr.^D Cynthia Qian, spokesperson for the Association of Ophthalmological Doctors of Quebec (AMOQ) and ophthalmologist specializing in retina at CHU Sainte-Justine and Maisonneuve-Rosemont hospital. “It burns right in the center of the viewer’s retina, and it affects central vision. » This is what causes solar retinopathy. The damage can be temporary or permanent “because the retinal cells do not regenerate”, recalls the D^D Qian.

What kind of glasses are safe?

Ordinary sunglasses, even with the best UV protection, are not sufficient to protect the eyes when viewing the Sun directly. The eclipse viewing glasses are equipped with an ISO 12312-2 certified filter. This filter is so opaque that only light emanating directly from the Sun is visible through it – it is 1000 times darker than ordinary solar lenses. “You should not try to be creative with things that are not designed specifically for looking at the Sun or the solar eclipse,” specifies the D^D Cynthia Qian. “People ask us, for example, if they can use X-ray film or photo film negatives, and make filters with superpositions of layers… The answer is no, it’s not safe. »

How can you be sure that these glasses are “real”?

When they have been obtained from a reliable supplier – for example, an astronomy store or a public institution – and are marked ISO 12312-2 and are not scratched or damaged, they should not be no problem. However, on March 22, the American Astronomy Society warned the population against the sale of counterfeit or non-compliant glasses on the internet. If in doubt about the reliability of the filters, the organization suggests this course of action:

1. Try on the glasses indoors. Nothing should be seen through it except the glow of very bright lights. If we can distinguish other details through the glasses filter, such as furniture or frames on a wall, the filter is not opaque enough.

2. If the glasses pass the test indoors, they can be tried outdoors. Here again, you shouldn’t see anything around you.

3. Looking up quickly at the Sun (less than a second), the Sun should appear to us as a well-shaped circle. Some filters give it a more orange appearance, others more white.

4. If the glasses have passed these three tests, they are “probably safe,” according to the American Astronomy Society. As a precaution, we suggest in this case not to look at the Sun during the partial eclipse for more than two or three seconds at a time, every five minutes.

Are the eyes protected if viewing the eclipse through binoculars, a telescope or a camera?

Only if the device in question is equipped with a suitable solar filter. For example, you should not look through an unprotected telescope while wearing eclipse viewing glasses.

What to do if you don’t have such glasses on the day of the eclipse?

This is not the end of the world. You simply need to avoid looking directly at the Sun during the partial eclipse. We can also follow the progress of the eclipse indirectly, by projecting the Sun’s light onto a wall or onto the ground through a hole punched in cardboard, or through other objects with holes, such as a colander. You can also make a darkroom out of a shoebox.

Watch the video from the Federation of Amateur Astronomers on ways to observe the eclipse

What if we are in the zone of totality? Can we look at the Sun without protective glasses?

So there, good news: during the total eclipse phase, and only when the Moon has completely covered the solar disk, we can look at the Sun without protective glasses. We can then admire the glow which surrounds a black circle.

The D^D Cynthia Qian, however, calls for great caution. “If people don’t know the exact time of totality and accidentally look at the Sun a few seconds too long after the total eclipse, that’s when they can injure their eyes. It is important to leave yourself a good safety margin if you decide to look at the Sun during the totality phase. »

Please note: the duration of the total eclipse varies greatly depending on the location of observation, from a few seconds to more than three minutes. During gatherings organized throughout the totality zone, facilitators will warn participants in particular when they can look at the Sun without glasses and when they must put them back on.

How do I know if I will be in the zone of totality?

Several geolocation methods exist online to know where you are in the path of the eclipse.

One of the easiest ways is to download the app My eclipsedesigned by the Federation of Amateur Astronomers of Quebec.

Download the app My eclipse

The Éclipse Québec site has also created a map with the main municipalities in the totality zone.

Check the map on Google

The Time and Date site also gives fairly precise indications on the start and end time of the eclipse, total or partial:

Visit the Time and Date website

“It’s a bit crazy at the moment”

In libraries, museums or specialized stores, they sold out quickly, sometimes within a few hours. To get your hands on a pair of eclipse viewing glasses less than two weeks before the big day, you now have to rely on a reduced list of suppliers.

At least 20,000 pairs on March 21, then another 30,000 pairs on March 25. The Certified Cartouches company continues to replenish its warehouse to meet the demand for eclipse glasses. “We’re pretty much the only ones to have them,” says Francis Bernier, director of commercial accounts for the Longueuil distributor.

After successfully selling medical equipment during the pandemic, this specialist supplier of printer cartridges became interested in eclipse viewing glasses earlier this year. “We did a first test, and we sold 40 pairs in two minutes. » An agreement was then concluded with two American manufacturers specializing in this type of equipment. “As with medical equipment, we knew that our customers would want to have a certified supplier. »

Eclipse viewing glasses must be equipped with an ISO 12312-2 certified filter. This filter is so opaque that only light emanating directly from the Sun is visible – it is 1000 times darker than ordinary solar lenses. Direct observation of the Sun without proper protection can cause permanent damage to the retina of the eye.

On March 22, the American Astronomy Society warned the population against the sale of counterfeit or non-compliant glasses on the internet.

Copies of protective glasses, imitating the graphics of certified glasses, have been spotted on online sales sites. For this reason, the Association of Ophthalmological Doctors of Quebec (AMOQ) recommends avoiding buying glasses on general sales sites such as Amazon or eBay.

“The source of supply is difficult to verify,” explains AMOQ spokesperson, D^D Cynthia Qian.

Respond to the request

Of the ten suppliers and institutions from which the Fédération des astronomers amateurs du Québec recommends obtaining glasses, the vast majority have exhausted their stocks. “It’s a bit crazy at the moment,” admits the president of Alco Prevention Canada, Stéphane Maître. About 250 eyeglass packages are shipped each day, and Mr. Maître expects demand to increase further in the coming week. Three additional employees were hired to handle glasses orders.

Orders come from individuals, but also from companies or institutions. “School boards, seniors’ residences, CEGEP co-ops…”, lists Francis Bernier. Certified Cartridges sells glasses in packs of 6, 50, 1000 or 10,000 pairs. A pack of six pairs sells for $27, or $4.50 per pair. The larger the package, the lower the unit price.

Despite interest increasing as the days go by, both companies expect to have enough glasses in stock to meet demand until April 8. In both cases, we are accepting online orders for glasses until Wednesday, April 3, to ensure postal delivery in time for the day of the eclipse.

After April 3, it will still be possible to obtain glasses directly from the premises of these suppliers, in Laval (for Alco Prévention Canada) and in Longueuil (for Certified Cartridges). Other points of sale will also be supplied in Quebec.