Is it safe to look at a total solar eclipse?

the The upcoming total solar eclipse This promises to be a once-in-a-lifetime experience, but viewing the celestial spectacle without proper eye protection can cause irreparable damage. Here's what experts say about the risks and how to monitor safely.

The Great North American Eclipse on April 8 It will be first visible from Earth in Mazatlán, Mexico, and from there it will travel northeast across the United States and reach Newfoundland, Canada. (Be sure to check out our eclipse viewing guide here.) The path of totality, where the entire eclipse is visible, will extend about 62 to 71 miles wide, but partial eclipse will be visible over most of the continent to varying degrees. This coincidence means that up to 31 million people will have the opportunity to watch this amazing event live, but this has experts worried.

Risk of permanent eye damage when looking at a solar eclipse

Viewing a solar eclipse is a rare and stunning event, but it poses significant risks to our eyes. Ronald Boehner, President American Optometric AssociationHe warns of the risks associated with viewing the eclipse without proper protection. Solar retinopathy, a condition caused by excessive exposure to light, can cause serious and often permanent damage to the retina, the sensitive layer of cells at the back of the eye. The retina plays a crucial role in the vision process, converting light into nerve signals that are then sent to the brain via the optic nerve.

“People want to go out and watch it, but there is some bad information about how to view the eclipse,” Benner explained to me. Some serious tips include wearing dark sunglasses, doubling up on dark sunglasses, or using a welding mask. “But none of this is true,” he warned.

When choosing eclipse glasses or handheld solar projectors, it is essential to ensure they adhere to specifications Global standard ISO 12312-2 And clearly display this certification for safe and reliable use. “Solar filters that provide a safe, comfortable, non-magnifying view of the Sun generally transmit between one part in 100,000 (0.001%) and one part in 2,000,000 (0.00005%) of visible sunlight,” explained Rick Feinberg, project manager for the American Astronomical Society. Community Solar Eclipse Task Force, in A statement. “These filters are at least 1,000 times darker than even the darkest sunglasses.”

Regular sunglasses, even when doubled, or welding masks, do not come remotely close to these filtration levels.

A false sense of security

The problem is that eclipses create a false sense of security. We usually don't stare at the sun because it's really uncomfortable, but that's not the case during an eclipse, when the moon blocks the sun a lot. It's easy to get the wrong impression that no light can harm our eyes. This misconception prompts many to remove their eclipse glasses, not realizing when the sun's full intensity will resume, a particularly risky behavior, according to Benner.

The retina, a very sensitive part of our eyes, is at risk during these events. “The retina is an extension of the brain, it's a pure neural network there,” he explained. “When we normally look at light, we get a chemical reaction that turns into an electrical reaction that sends a signal to the brain. Unfortunately, this delicate structure can be damaged beyond repair.” Due to intense light, incoming rays can “burn” this tissue, leading to inflammation and dysfunction of the rods and cones, which are light-sensitive cells in the retina. This damage can be permanent, as these cells may die, particularly affecting vision. Colors if cones are damaged.

According to 2013 Stady Published in Case Reports in OphthalmologySolar retinopathy often goes unnoticed at first because its symptoms are subtle and easily overlooked. This makes diagnosis difficult, because damage from light or heat does not always appear severe at first. Despite its deceptively mild appearance, it is a serious eye condition. Unlike the skin or corneal epithelium, which can regenerate, damage to the retina does not show immediate symptoms, often resulting in delayed perception of permanent vision loss or changes such as distorted color perception.

“Most people with solar retinopathy don't really know when they got it,” Penner said. The damage is not immediately painful, resulting in delayed awareness. He likened it to a sunburn, where it is not clear that the damage has occurred until several hours later. When seeking medical help, doctors may identify inflammation and evaluate possible recovery of nerve tissue, but the eye's nerve network may only partially recover, if at all. Over time, this unresolved damage can lead to scarring, resulting in visual impairment such as “holes” in the vision.

The most serious consequence of solar retinopathy is loss of central vision. Penner likens this to punching a hole in an old photographic negative using a paper punch. Other effects include permanent changes in color perception, blurred vision, light sensitivity, and headaches.

“Once those tissues are damaged, it's up to the body to try to repair them. There's no medicine, there's no cure, there's no solutions. That's why we take this seriously, because once it's done, it's done.”

“Not worth the risk”

The risks are particularly concerning for children. Parents may be keen for their children to witness the eclipse but they need to guide and control them effectively. “What's really scary for me is when parents take their kids outside, because they want their kids to experience that. But if you're trying to manage three or four or five kids at the time, and making sure all the kids are following the instructions of what they're supposed to do, Children don't always understand the consequences. In fact, these guidelines are complex enough for adults, let alone children.

There is great concern for those outside the path of totality who may underestimate the damage caused by looking at the eclipse without proper protection. For those observing the eclipse from within the path of totality, they also may not be fully aware of the potential risks, Penner warned. “It's difficult to pinpoint the point at which sunlight becomes harmful. So, avoid taking any risks.” “If you're keen to watch the eclipse closely, it's safe to watch it on TV or online.” He urges making the experience a positive and safe one, not an unfortunate one. Do not observe the eclipse with unprotected eyes, even during the total eclipse.

American Academy of Ophthalmology He offers slightly different advice, claiming that observers can safely see the Sun without protection only during a total eclipse when the Moon completely obscures the rising face of the Sun, i.e. during a total eclipse. Once the sun begins to rise, observers should put their eclipse glasses back on to view the remaining partial phase of the eclipse.

However, Benner's advice is clear and reasonable: “Don't let it turn into a negative experience that you have to live with for the rest of your life.” So enjoy the upcoming eclipse, but remember to do so safely using proper eye protection without risking your vision. And remember that important string of letters and numbers: ISO 12312-2.

A version of this article originally appeared on Gizmodo.