DALLAS (AP) 鈥 Millions of people along a narrow band in North America will look up when the sky darkens during a total solar eclipse on April 8. When they do, safety is key.
Staring directly at the sun during a solar eclipse or at any other time can lead to permanent eye damage. The eclipse is only , or the period of total darkness when the moon completely covers the sun.
Those eager to should . Sunglasses are not protective enough, and binoculars and telescopes without a proper solar filter can magnify light from the sun, making them unsafe.
鈥淧lease, please put those glasses on,鈥 NASA Administrator Bill Nelson said.
Where to find eclipse glasses
Since counterfeit glasses abound, consider purchasing glasses from a local science museum or order online from a seller cleared on the American Astronomical Society鈥檚 website.
Eclipse safety experts say legitimate eclipse glasses should block out ultraviolet light from the sun and nearly all visible light. When worn indoors, only very bright lights should be faintly visible 鈥 not household furniture or wallpaper.
Old eclipse glasses from the or October's are safe to reuse, as long as they aren't warped and don't have scratches or holes.
Glasses should say they comply with ISO 12312-2 standards, though fake suppliers can also print this language on their products. NASA does not approve or certify eclipse glasses.
How to view the eclipse without glasses
If you don't have eclipse glasses, you can still enjoy the spectacle through indirect ways such as making a pinhole projector using household materials.
Poke a hole through a piece of cardstock or cardboard, hold it up during the eclipse and look down to see a partial crescent projected below. Holding up a colander or a cracker will produce a similar effect.
Another trick: Peering at the ground under a shady tree can yield crescent shadows as the sunlight filters through branches and leaves.
Eye experts warn against viewing the eclipse through a phone camera. The sun鈥檚 bright rays can also damage a phone鈥檚 digital components.
Why looking at a solar eclipse is dangerous
Eye damage can occur without proper protection. The sun's bright rays can burn cells in the retina at the back of the eye. The retina doesn鈥檛 have pain receptors, so there鈥檚 no way to feel the damage as it happens. Once the cells die, they don鈥檛 come back.
Symptoms of solar eye damage, called solar retinopathy, include blurred vision and color distortion.
In a rare case of eclipse eye damage, a woman who viewed the 2017 eclipse without adequate protection came to Mount Sinai鈥檚 New York Eye and Ear Infirmary, complaining of a black spot in her vision. Doctors discovered retinal damage that corresponded to the eclipse鈥檚 shape.
鈥淭he dark spot she was describing was in the shape of a crescent,鈥 said Dr. Avnish Deobhakta, a Mount Sinai ophthalmologist.
There鈥檚 no set rule for how long of a glance can lead to permanent damage. Severity varies based on cloudiness, air pollution and a person's vantage point.
But doctors say looking at a solar eclipse for even a few seconds unprotected isn鈥檛 worth the risk. There are reports of solar retinopathy after every solar eclipse, and U.S. eye doctors saw dozens of extra visits after the one in 2017.
Spectators who plan ahead can secure a stress-free eclipse viewing experience.
鈥淚t can be dangerous if we aren鈥檛 careful, but it鈥檚 also very safe if we take the basic precautions,鈥 said Dr. Geoffrey Emerson, a board member of the American Society of Retina Specialists.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute鈥檚 Science and Educational Media Group. The AP is solely responsible for all content.
