This story has been updated.
The Great American Solar Eclipsewill pass over Bloomington on April 8th, and while an estimated 300,000 people are traveling to watch the natural phenomenon, experts warn that watching without the proper eyewear can be dangerous.
“The main thing would be prevention,” assistant professor at the Indiana University School of Optometry Dr. Hin Cheung said. “During an eclipse when there is something to look at, it's really important to wear safety eyewear.”
It is unsafe to view a partial solar eclipse through regular glasses, camera lenses, telescopes, or binoculars without the necessary filters. The only time it is safe to view the eclipse without proper eyewear is during totality, when the moon completely blocks the sun.
Read more: Gearing up for the eclipse? Start here
Looking at the solar eclipse through a lens without the proper filter can actually be more dangerous than looking at the eclipse with a bare eye.
“Without the filter, you can actually cause more damage to your eyes by looking through those devices, because their job is to help you focus more light into that device to be able to see something clearly,” Cheung said. “That can actually magnify the damage potentially.”
The effects of looking at the solar eclipse without the proper eyewear may be unnoticeable, until hours — or even days — later when there are signs of vision loss, distorted vision or altered color vision.
“If you think about the eye, like a camera…the retina is like the film to a camera. So that's going to generate what we see like a photograph,” Cheung said. “If you damage the film, you're going to damage the photograph. In our case, it's going to damage our vision.”
Read more: What kind of eclipse glasses should I get?
This condition is known as solar retinopathy. The sun damages the retina, which is the part of your eye that transmits information to the brain. Its effects can be permanent and cannot be cured.
“No amount of glasses, contacts or surgery can fix that,” Cheung said.
To watch the eclipse safely, solar eclipse filters and glasses are necessary to protect the eyes.
To avoid buying counterfeit glasses from sites such as Amazon, Cheung recommends buying from the American Astronomical Society’s list of reputable vendors.
For children, who need to be watched closely during the solar eclipse, the best way to protect their eyes is to view the eclipse indirectly.
This can be done using a pinhole projector. Here, instead of looking at the sun directly, viewers can look at a projection of the sun or a shadow of the eclipse, Cheung said.
“If you just put your fingers together… into a waffle shape, there are little holes between the fingers… the little holes between your fingers are going to project an image of the sun,” he said. “As the eclipse occurs, it's going to show a little crescent shape that's going to change over time as the eclipse is happening.”
Glasses from the previous solar eclipse in 2017 can still be used, under a few conditions. They must meet a specific worldwide standard known as ISO 12312-2, and have no expiration date on them.
Also, to check if glasses are safe to use, hold them up to a light and ensure that there is no light peeking through the lenses of the glasses. There should be no cracks or damage on the glasses.
Solar eclipse glasses can be picked up for free at the Brown County Visitor Center, and at IU's Science Fest on April 6. Additionally, the Wonderlab Museum and the Bloomington Parks and Recreation Main Office will be selling glasses in packs and individually respectively.
CLARIFICATION: Original article did not include that solar eclipse glasses can be removed during totality, when the moon completely blocks the sun.
