There is one very important thing to look for when shopping for glasses to view the April 8 solar eclipse -- the letters and numbers ISO 12312-2.
ISO stands for International Organization for Standardization, a group of global experts who "agree on the best way of doing things -- for anything from making a product to managing a process," according to the ISO website. The nongovernmental organization was created in 1946.
Solar eclipse glasses recently obtained from a local pharmacy, a Central Arkansas Library branch and from Blue Cross and Blue Shield of Arkansas all include the ISO 12312-2 designation. Each pair of those glasses bears the designation, as well as the ISO logo, on the interior left temple, or arm.
Dr. Wade Brock, an ophthalmologist, oculoplastic and facial cosmetic surgeon, offered several safety precautions for viewing the solar eclipse:
Even the darkest sunglasses you have are not suitable for observing the sun directly.
Never look at the sun through an unfiltered camera, telescope, pair of binoculars or similar device, even if you are wearing eclipse glasses. The intensified solar rays can damage your filter and your eyes.
Staring at the sun for even a short time without wearing the proper eye protection can damage your retina permanently; this damage can include loss of vision or blindness.
For glasses to be safe they must meet the worldwide standard known as ISO 12312-2. The American Astronomical Society provides a list of reliable manufacturers (eclipse.aas.org/eye-safety/viewers-filters).
"For anybody -- whether you are nearsighted, farsighted or see great -- the sun is strong enough to actually burn your retina and that can cause a solar retinopathy and that can cause permanent blindness," says Brock, who has practiced in Little Rock since 2004. "It doesn't necessarily hurt while it is happening but you will have two or three days of really bad vision and it can be irreversible."
Dr. Paul Phillips, director of the Harvey and Bernice Jones Eye Institute at the University of Arkansas for Medical Sciences, specifies that only ISO 12312-2 glasses that completely cover the eyes should be worn for viewing the April 8 eclipse.
"Even the dark glasses you get from your eye doctor after you are dilated will not suffice. It specifically must be made for viewing the eclipse. It should completely cover your eyes," Phillips says. "If you wear glasses, you can put them over your glasses, but they should completely cover your eyes when viewing. Otherwise, you should not directly view the eclipse.
"It is important that they cover your eyes before you view and you keep them on until you are done viewing. So basically cover your eyes and then look up and when you are done, look away then pull them off."
A total solar eclipse happens when the moon passes between the sun and earth, completely blocking the face of the sun. It's the only type of solar eclipse where viewers can momentarily remove their eclipse glasses or viewers for a brief period of time when the moon is completely blocking the sun, according to the American Optometric Association. But both Brock and Phillips caution against removing approved solar eclipse glasses even then because of the likelihood of human error.
"There is too much room for misinterpretation," Phillips says. "It can cause a solar burn in the center of your retina and that's where you can have permanent loss of vision."
Phillips says he has seen patients with laser burns that occurred "not just during [an] eclipse but from any kind of sun gazing. Sometimes we have a child who just happens to look up for even just two or three minutes.
"Most people outside of the eclipse cannot do that. It is uncomfortable. It is really just during the eclipse because their attention is drawn up toward viewing the sun," he adds. "Because you've got partial blockage it can be a little more comfortable to view the sun, but it is still not safe -- and that's the danger."
As does Brock, Phillips notes that the burning may not be felt during its occurrence.
"You think everything is fine, your eyes are not hurting but the sun can burn. It can cause some corneal burns, too -- the front of the eye. But the most dangerous thing is the burn on your retina."
Phillips says he is worried that some people may decide to look at the eclipse without glasses because it does not cause discomfort.
"If you look up at the sun and it is uncomfortable, you look away. I think what's deceiving here is you can look up when you've got a lot of coverage -- but not complete coverage -- and it can be pretty comfortable. You may think everything is fine while it burns a hole through your retina. I think the key is you use the protection, completely cover the eyes and that's the way to view it."
Parents should be particularly vigilant about making sure their children keep the eclipse glasses on at all times, he says.
The American Optometric Association offers several other tips:
-- Inspect the eclipse glasses before use and do not use them if they are torn, scratched or damaged.
-- Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up. After viewing, turn away and remove your glasses or viewer -- do not remove them while looking at the sun. If you normally wear eyeglasses, wear your eclipse glasses over them or hold your handheld viewer in front of them.
-- If you should experience discomfort or vision problems following the eclipse, visit your local doctor of optometry or ophthalmologist for a comprehensive eye examination.
-- All symptoms should be treated as urgent until viewed by a doctor of optometry or ophthalmologist.
Another safe option for viewing the eclipse is to make a pinhole projector with two pieces of stiff cardboard like paper plates. Take one piece of cardboard and use a pin or thumbtack to make a small, round hole in the center. With your back toward the sun, hold one piece of paper above your shoulder, allowing the sun to shine on the paper.
The second sheet of paper will act as a screen. Hold it at a distance, and you will see an inverted image of the sun projected on the paper screen through the pinhole. To make the image of the sun larger, hold the screen paper farther away from the paper with the pinhole.
"But there is nothing that is going to be as exciting as having your glasses and looking at the eclipse when it happens," Brock says.
For more information on solar eclipses and eye safety, visit aoa.org/healthy-eyes/caring-for-your-eyes/solar-eclipses.