Children and young adults are most likely of all age groups to suffer from blindness when they look at the sun during a solar eclipse, according to NASA.
"Eclipse blindness" can occur when people look at solar eclipses repeatedly or for a long time without proper protection. It can be temporary or permanent, and it is particularly dangerous because the damage to the eyes happens without any pain, according to B. Ralph Chou, an optometry
professor who wrote a report for NASA.
The blindness does not occur "for at least several hours after the damage is done," Chou wrote.
"The danger to vision is significant," Chou wrote. "This can have important adverse effects on career choices and earning potential, since it
has been shown that most individuals who sustain eclipse-related eye injuries are children and young adults."
The studies Chou cited were one in 1966 titled "Eclipse blindness – Report of an epidemic in the military population of Hawaii" and "Eye
injuries in Canada following the total solar eclipse" of Feb. 26, 1979.
The intense light from the sun, Chou wrote, triggers chemical reactions in the eyes that can damage or destroy the eye cells needed for sight,
and can cause temporary or permanent blindness.
Also, the bright light and radiation from the sun can cause "heating that literally cooks the exposed tissue" of the eye.
Depending on where you are in the world, Sunday's event will either be partial or a full "ring of fire" eclipse, where the moon’s shadow
obscures the center of the sun except for a "ring" that leaves the sun’s outer edge visible. It is never safe to look at either eclipse without
proper equipment, Chou wrote.
"Even when 99% of the Sun's surface ... is obscured during the partial phases of a solar eclipse, the remaining crescent Sun is still intense
enough to cause a retinal burn, even though illumination levels are comparable to twilight," Chou said.
Don't try to make your own makeshift filters to watch the sun directly, such as using multiple sunglasses, the Griffith Observatory says. That
won't work. Other unsafe methods include using smoked glass, X-ray images, or photographic film. The only safe filter blocks all but 0.003% of
the visible light.
"The fact that the Sun appears dim, or that you feel no discomfort … is no guarantee that your eyes are safe," Chou wrote.
Here are some options on how to view the eclipse safely:
The simplest way is to project the eclipse on a surface, so you don't look at the sun directly.
The simplest way is to criss-cross your fingers waffle style to the sunlight, which will project the partial eclipse on the ground in front of
you, according to a NASA video on Sunday's eclipse.
You can also get a piece of cardboard, punch a nail through it, and then angle the cardboard to project the sun's light on another piece of
cardboard. "You'll see a projected image … when the sun goes into eclipse, you'll see a crescent," said Griffith Observatory director Ed Krupp.
The smaller the hole, the sharper image you can get. A more elaborate version can be found here.
Another easy method: using a hand mirror to reflect the light of the sun onto a wall or some other surface, Krupp said.
Another idea is to use binoculars to project an image of the sun on a surface, NASA says. Just don't use the binoculars to look at the sun
If you want to look at the sun directly, here are some options:
The Griffith Observatory, which is run by the city of Los Angeles, will also have, for free, telescopes with specially designed filters for
people to watch the eclipse directly.
But eclipse sunglasses are hard to come by. The observatory has sold out of eclipse glasses, which were selling for $2.99 a pair, said
spokeswoman Susan Szotyori.
Griffith Observatory is open Saturday from 10 a.m. to 10 p.m., and on Sunday opens at 10 a.m. and will be open through the partial solar eclipse Sunday evening, which begins at 5:24 p.m. and reaches its maximum shadow at 6:38 p.m.
So-called "No. 14" welder's glass can also be used to look directly at the sun.
And by the way -- don't throw your eclipse glasses away. Another rare cosmic sight will occur soon -- Venus move between the Earth and the Sun on June 5, and we will able to see a dark dot float across the surface of the sun. It will be the last such occurrence in our lifetime, says transitofvenus.org. The transit will be visible in the continental United States, Central America, most of Europe except for Spain and Portugal, eastern Africa, the Middle East, central Asia, parts of southeast Asia, western Australia and India.