Solar eclipse: How to safely view a total eclipse

Total solar eclipses happen every few years somewhere on the planet.

But, if there’s one happening near you, it’s worth making plans to view and enjoy it with proper eye safety to avoid losing your vision permanently.

It can sometimes take hundreds of years before a total solar eclipse returns to the same spot, according to NASA, so it’s a once-in-a-lifetime opportunity for many of us.

On April 8, 2024, a total solar eclipse will cross a large portion of North America (including a large swath of Ohio) with a path ranging between 108 and 122 miles in width, according to NASA.

Hear an Ohio State astronomer explain why this solar eclipse is special

What happens during a total solar eclipse?

When there’s a total solar eclipse, the moon passes between the sun and Earth, completely obstructing the sun’s face. The sky will become dark as if it’s dawn or dusk.

If you’re in the direct path, it will become dark for about four and a half minutes, according to NASA. The period of darkness is shorter the farther you are from the eclipse’s direct path.

Nocturnal animals may become active, and the temperature often drops by 10 degrees.

What happens to your eyes when you stare directly at the sun?

You should never look directly at the sun, even on a normal day, because there is potential risk to damage your retina, says Aaron Zimmerman, OD, clinical professor at The Ohio State University College of Optometry and chief of contact lens service.

“The sun is usually uninteresting and is so bright and uncomfortable that humans don’t look directly at it,” Dr. Zimmerman says. “Of course, there are times when you accidentally look at it, or it’s reflected, and it’s uncomfortable, but we quickly look away from it and this short exposure doesn’t result in harm.”

It’s when we stare longer at a bright light source, such as the sun or a laser, that there’s damage, says Sayoko Moroi, MD, PhD, professor and chair of Ophthalmology and Visual Sciences at The Ohio State University Wexner Medical Center.

“Light can induce damage or burns to the retina when you look directly at the light source. The center part of the retina is most vulnerable, because that's where we focus for the best vision,” Dr. Moroi says.

That damage accumulates the longer you stare at the light source.

“During an eclipse, people look at the sun for a few seconds at a time,” Dr. Zimmerman says. “Over the course of 3.5 hours, someone may make repetitive glances at the various stages of the eclipse and, once the event is over, that person may have cumulatively looked at the sun for minutes – far exceeding the safe viewing time.”

The damage to the retina is permanent because the light induces free radical damage that kills the cells.

“You don't recover from it. Once the retina is damaged, it's damaged,” Dr. Moroi says. “Enough exposure to light can actually cause damage to the retina as well as the layer next to that, called the retinal pigment epithelium, and this damage leads to loss of vision.”

People who have impaired vision after viewing an eclipse unprotected are often left with long-lasting afterimages, blurry vision, or are even missing a portion of their center vision, meaning they can see around an area but that there’s a significant blind spot.

Long-term, it would be difficult to read without magnification, Dr. Moroi says.

The only time that is safe to view the solar eclipse without eyewear is during the brief totality phase. That's when the moon completely blocks the sun for a matter of minutes.

While you can suffer from eye damage anytime you get too much light exposure from the sun, solar eclipses can be misleading to your eyes.

We all have a natural instinct to squint when there’s bright light. It’s known as photophobia. But we seem to ignore that instinct during an eclipse.

“The photophobic response does not go away, but humans can overcome the aversion to light response and willfully look at the eclipse,” Dr. Zimmerman says. “Unfortunately, without proper eye protection, viewing the eclipse can cause permanent damage to the retina.

“You may not immediately realize you’ve exposed your eyes to too much light, and later you discover that you have vision changes or loss.”

What’s the best way to safely view the solar eclipse?

• Use eclipse glasses and viewers from a reputable source, according to the American Academy of Ophthalmology and the American Academy of Optometry.
• In partnership with the American Astronomical Society, the recommendation is to purchase eclipse glasses from a verified list of companies that are known to adhere to International Organization for Standardization standards. North America-based companies selling eclipse glasses can be found here:
• American Paper Optics / eclipseglasses.com
• DayStar Filters
• Flip’n Shades (clip-ons for baseball caps)
• Rainbow Symphony
• Thousand Oaks Optical
• Seymour Solar (sheets only)
• Check to see if your local library is giving out eclipse glasses. The Space Science Institute’s National Center for Interactive Learning has distributed more than 5 million free eclipse glasses to more than 10,000 libraries across the country ahead of the April 8 eclipse.

Can you reuse eclipse glasses from the 2017 partial solar eclipse?

If you notice that your eclipse glasses are scratched and damaged in any way, don’t use them. It’s not worth risking damage to your eyes.

“As long as the lenses aren’t torn or punctured, then they will work just fine. If you can comfortably view the sun with them, then they will protect you,” Dr. Zimmerman says.

Can you use regular sunglasses to watch the eclipse?

Don’t try using normal sunglasses or other substitutes. Regular sunglasses won’t protect your retinas.

Can you use eclipse glasses with a telescope, camera or binoculars?

If you plan to use camera lenses, binoculars or telescopes during the eclipse, you must use solar filters specially designed for your equipment. It’s not enough to use solar eclipse glasses to look through a camera, binoculars or a telescope. The sun can still damage your eyes.

If you don’t have solar eclipse glasses, here are some safe ways to still enjoy the eclipse

• Make a pinhole projector
• Use welder’s glass with shade numbers 12 to 14 to view a solar eclipse.
• Safely view the eclipse through the eyes of NASA online.
• Do not use a telescope or binoculars unless they have proper filters.

On eclipse day, don’t forget about sunscreen

If you’re outside for hours monitoring the total solar eclipse path, make sure you’re wearing plenty of sunscreen and protective clothing to shield your skin such as long sleeves or hats. The sun will be as bright as usual on eclipse day.

Apply higher SPF (SPF 50+) sunscreen with broad-spectrum UVA/UVB coverage over any sun-exposed skin if you plan to watch the eclipse for a few hours, says Susan Massick, MD, a dermatologist at The Ohio State University Wexner Medical Center and an associate professor at The Ohio State University College of Medicine.

“Apply 20 minutes before you head outside and be sure to reapply every two to three hours throughout the day,” she says.