Can you really go blind from looking at a solar eclipse? Real life cautionary tales.

Editor's note: An updated cloud forecast for the April 2024 total solar eclipse is in. Read the latest eclipse forecast and news as of Monday, April 8.

When the ophthalmologist looked into a 26-year-old's eye in 2017, it was a worst-case scenario. The distinctive contours of the solar eclipse the woman stared at days prior were etched onto her retina.

The case of the Staten Island woman who watched the eclipse through faulty glasses was notable enough to be chronicled by doctors from Mount Sinai's New York Eye and Ear Infirmary in JAMA Ophthalmology, a medical journal, because these cases are, luckily, rare.

“It's a very focused beam of high-energy light from the sun itself,” said Dr. Avnish Deobhakta, an ophthalmologist at the Mount Sinai infirmary who treated the woman. “It can actually destroy parts of the retina, and certainly destroy it in the shape of an eclipse.”

The woman told Mount Sinai doctors she had gazed at the moon passing in front of the sun through what she believed were protective glasses. In scans, the damage on her left retina, the area at the back of the eye where the brain receives images, resembled the shape of a partial eclipse. She told a local TV station that year when she closed her eyes, she saw a sun-eating-moon image that "looked like Pac-Man" or "a crescent moon."

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Looking up when you're within the 115-mile-wide path when the moon completely covers the sun for a few minutes is safe, experts say. But directly staring at the sun before and after the total eclipse, or watching a partial eclipse outside the path of totality without proper eye protection can result in permanent damage including blurred and altered vision.

While rare, eye damage from watching a partial eclipse happens because a person's natural response to squint when looking at sunlight does not get triggered. In the leadup to the April 8 solar eclipse, doctors and a rare set of eclipse watchers are warning about watching this planetary event without adequate eclipse glasses or with the naked eye.

It’s hard for experts to know or even estimate how many people experience eye damage from solar eclipses. Since looking at an eclipse does not cause complete blindness, people with permanent damage may not know they have it or report it to a doctor. The 2017 eclipse, which passed from Oregon to South Carolina, is thought to have caused about 100 cases, according to the American Astronomical Society. A national survey by NASA and the University of Michigan estimated over 150 million people witnessed that eclipse.

The 2024 eclipse is expected to have more people watching because it is passing over several large cities in the U.S. and Mexico.

Experts urge people to plan before they head outside to stare at the sun.

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“Human nature is to take a shortcut anywhere we can,” Dr. Ron Benner, an optometrist in Montana and the president of the American Optometric Association, a professional group, told USA TODAY. “But in this case, shortcuts can cause permanent damage.”

Deceptive, dangerous light

When there isn’t an eclipse, humans naturally squint or are forced to look away from the sun’s brightness. People often also wear sunglasses to protect against harmful UV rays.

But during a partial eclipse, the moon’s shadow allows people to stare at the sun longer without experiencing that intense glare. The high-energy rays cast down during that time are akin to a laser pinpointing at the eye. Without feeling the usual sting in their eyes, people are exposed to harmful rays for a longer period, Deobhakta said.

There's a misconception that eye damage of this nature is a sunburn, said Benner, from the optometric association. Dangerous light and radiation exposure, when you turn your eyes directly to the sun, can permanently damage retinal cells at the back of the eye. The retina plays an essential role in helping the brain process images.

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About four hours after the Staten Island woman watched the eclipse – with glasses she thought were protective – her vision became blurry and color distorted, according to the JAMA study from Mount Sinai.

The safest way to avoid eye damage, is, of course, not looking at the partial eclipse. Although few are as cautious as eye experts, Deobhakta and Benner recommend watching the upcoming eclipse on TV. They both also suggest that millions who plan to watch in person take steps to protect themselves against eye damage.

A very safe way to watch is to turn your back to the eclipse and watch its shadows using a pinhole projection of light. You can create a pinhole by crisscrossing your fingers and letting the light project through them onto the ground. You can also hold up an index card with a hole in it or a pasta colander or any item with small holes and let the sunlight pass through it onto the ground or a wall.

You can also use specially designed glasses. The American Astronomical Society publishes a list of approved glasses that meet the international standard of ISO 12312-2, meaning they will protect your eyes from injury and provide a comfortable view of the eclipse.

Rick Fienberg, project manager for the American Astronomical Society’s solar eclipse task force, reviews reports on the glasses to ensure they’ve been adequately tested.

“It’s a bit of a jungle out there, but there’s more than 100 suppliers listed on our site,” said Fienberg, who’s watched 14 prior eclipses and plans to watch the April eclipse in Mexico. “There’s no reason to just go to Amazon, Google or Etsy, or anything, and search for eclipse glasses.”

He suggests going to that list and buying directly from a manufacturer. The astronomical society also recently warned of counterfeit glasses and offered guidance on spotting unsafe products.

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'A personal involvement with Mr. Sun'

Childhood friends Lou Tomososki and Roger Duvall, both 77, have told cautionary tales for years about the day in the early 1960s when each of them burned an eye squinting up at a partial solar eclipse.

The two men, teenagers at the time, watched without protection, from the baseball diamond at their high school in Portland, Oregon. Tomososki, a retired semi-truck driver, and Duvall, a former employee at a rental car company, remember their science teacher telling them about the upcoming eclipse and warning about eye damage.

After looking at the eclipse for about 20 seconds, Tomososki developed a grayish spot in the middle of his right eye, while Duvall now has a similar dark spot in his left eye. Duvall said he visited a doctor the day after the eclipse when he noticed his vision loss.

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Despite the eye damage, both men served in the military after high school. Most of the time, they don't think about the damage. It's only when they close an eye that they notice it.

During a phone interview, Tomososki mentioned that he was looking at a daffodil from afar, but the blot in the middle of his eye blocked the yellow bulb. Instead, that portion of the flower looked like when a person's face is blurred on TV.

Both men have made it a point to warn people about eclipses. They will surely be warning folks again this year.

“I'm more aware of it than your average person walking down the street,” Tomososki said. “Because I got kind of a personal involvement with Mr. Sun.”

This article originally appeared on USA TODAY: Can you go blind from a solar eclipse? Doctors' tips, watchers' tales.