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Eclipse glasses with a special ISO filter should be worn when viewing the total solar eclipse to avoid eye damage. Leo Patrizi/Getty Images
  • A total solar eclipse will travel across North America on April 8, 2024, with the path of totality visible in several major U.S. cities.
  • When viewing a solar eclipse, eye safety should be a top priority to avoid permanent damage caused by solar retinopathy.
  • Eclipse glasses should have a special ISO filter to prevent harmful ultraviolet and infrared light from penetrating the retina.
  • It is unsafe to look directly at the sun without proper eye protection, even during eclipses.

On Monday, April 8, the total solar eclipse of 2024 will sweep across a large swath of North America.

During this astronomical event, the moon will pass between the sun and Earth, darkening the sky in significant portions of the United States from Texas to Maine.

If the conditions are clear, viewers may also get a glimpse of Venus and Jupiter.

More than half the U.S. population lives within 250 miles of the 115-mile wide path of totality, including major cities like Austin, Dallas, Indianapolis, Cleveland, Buffalo, Rochester, and Burlington, VT.

The duration of totality will be up to 4 minutes and 27 seconds, nearly double that of The Great American Eclipse of August 21, 2017, which drew an estimated 20 million spectators. According to NASA, the next total solar eclipse visible in the U.S. won’t occur until August 23, 2044.

When viewing solar eclipses, it’s important to wear specialized protective eyewear to prevent eye damage. Looking directly at the sun without eye protection could result in immediate and irreversible eye damage. Here’s what you need to know to protect your eyes during the total solar eclipse.

Reminiscent of cardboard 3D viewing glasses, eclipse glasses are essential for protecting your eyes while viewing a solar eclipse.

There are countless options of eclipse glasses available online and it may be difficult to determine which ones are safe and legitimate. When choosing protective eyewear, look for reputable sources that have been certified with the solar filter ISO 12312-2, which is the international standard for eclipse viewing glasses.

If you plan to take pictures of the eclipse or view it through any type of lens, such as a telescope or binoculars, you should cover the lens with a special solar filter to avoid eye injury.

You should never look directly at the sun without proper protective eyewear, even during solar eclipses. Sunglasses or homemade eclipse glasses do not provide sufficient protection.

Although the moon obscures the sun’s brightness during an eclipse, it does not minimize the effects of the sun’s energy.

Eclipse glasses that meet the ISO 12312-2 standard limit the ultraviolet and infrared wavelengths that reach the retina and filter most of the sun’s energy to prevent damage to the retina.

Benjamin Bert, MD, board certified ophthalmologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA, told Healthline the biggest danger of looking at the sun without proper protective eyewear is solar retinopathy, which essentially burns the retina.

He said he’s seen a spike in patients with eye damage following prior solar eclipses.

Bert compared solar retinopathy to using a magnifying glass to focus sunlight onto a sheet of paper until it catches fire. “You’re basically doing that to your eye,” he said. “And that burn is permanent. You can lose a spot in your vision if it gets burned like that. Once the damage is done, we currently don’t have any way to reverse it.”

Your safest bet for eclipse viewing is to purchase a new pair of eclipse glasses with the certified ISO 12312-2 filter.

If you’ve been hanging onto your old eclipse glasses from 2017’s Great American Solar Eclipse, you’ll want to ensure they’re in good condition before reusing them.

Check for defects and damage and make sure there are no scratches, punctures, or tears in the filters.

If the frames are bent or appear anything less than brand new, it’s time for a new pair.

When the moon completely blocks the face of the sun during totality, what remains is the glowing halo of the sun’s corona, or atmosphere.

Eclipse viewers should keep their glasses on during the partial phases of the eclipse, roughly 75 minutes before and after totality.

You can determine when the partial phase will begin in your observing location with an eclipse calculator.

According to NASA, it is safe to remove eclipse glasses during totality, but only if you are in the path of 100% totality.

Astrophysicist Jamie Lombardi, PhD, professor of physics at Allegheny College in Meadville, PA, explained that during totality, eclipse viewers are shielded from the sun’s intense visible light, ultraviolet radiation, and infrared radiation.

“Although the corona is still visible, it is much dimmer than the disk of the sun and is safe to view with the naked eye,” Lombardi told Healthline.

Bryan Brewer, author of “ECLIPSE: Experience Awe in the Path of Totality,“ agreed it’s safe to remove your eclipse glasses during totality to view this celestial spectacle.

“The eerie daytime darkness — punctuated by the magnificent view of the solar corona for just a few minutes — illustrates the awesome and relentless forces of the cosmos in a dramatic and accessible way,” Brewer told Healthline.

Yehia Hashad, MD, Chief Medical Officer at Bausch + Lomb, explained that when the moon fully blocks the sun’s rays during totality, it’s OK to view the corona without protective eyewear, but you should remain vigilant.

“If there is any portion of the sun visible, the rays can be very damaging,” Hashad told Healthline.

“If you are at all uncertain if the sun is 100% covered, always revert to leaving your protective glasses on. The safest course of action is to wear your protective glasses throughout the event — you will still have quite a show,” Hashad noted.

Bert echoed this sentiment, and advised against looking at the corona during totality altogether without protective eyewear.

“Even if you’re in truly complete totality, the safest thing to do is just to leave them on. You can take them off, but don’t gaze at the sun,” Bert said.

“If you’re planning on looking at the sun, wearing the glasses the whole time is certainly the safest option. That’s probably an extreme opinion, but when the risk is the potential for permanent retinal damage, you want to take every precaution that you can. It’s not worth the potential harm that can be done for the 5 minutes you would be able to see it,” Bert cautioned.

You can safely view the effects of the eclipse indirectly without the need for protective eyewear.

A box pinhole projector is a popular indirect eclipse viewing method.

A pinhole projector allows you to safely observe the light generated by an eclipse through a small hole in an object onto a surface. This method results in shadows of tiny half-moons projected onto the ground or a wall.

“That’s a much, much safer way to do it because you’re not gazing at the sun at all; you’re gazing at shadows,” Bert said.

Solar retinopathy develops when the retina becomes damaged by exposure to solar radiation. The condition may cause permanent blind spots, distortion in your vision, or partial or full blindness, Hashad said.

“Additional symptoms include blurred vision, increased light sensitivity, central blind spots in either or both eyes, distortions, and may change the way colors are viewed,” he added.

According to Bert, there are telltale signs of eye damage from solar retinopathy caused by eclipse viewing.

If you see little spots of flashing light, similar to the after-effects of a camera flash, you may have sustained eye damage.

If the initial flashing lights resolve but the areas that were flashing remain dark, like spots in your vision, it could be a sign that permanent damage has occurred, which may warrant a visit to your ophthalmologist.

Bert said if at any point during an eclipse viewing you begin to see little flashes of light or the experience becomes uncomfortable, you should look away from the sun immediately.

A total solar eclipse occurs on April 8, 2024 with the path of totality crossing a large region of the United States.

Whether viewing a partial or total solar eclipse, prioritizing eye safety can prevent permanent damage from solar retinopathy.

If you plan to participate in this astronomical event, wear eclipse glasses with an ISO 12312-2 filter when looking at the sun, and do not remove your glasses until after you’ve looked away. If using binoculars, a telescope, or a camera of any kind, an appropriate solar filter should be applied to the lens.

Of course, you should also wear sunscreen and sun-protective clothing if spending more than a few minutes outside.

“A total solar eclipse is an exciting and rare event that people should certainly experience if they’re motivated to do so,” Hashad said. “I would just encourage everyone to do their research and be mindful of their eye health when viewing.”

Additional safety guidelines for watching the total solar eclipse 2024 can be found on NASA’s website.