Officials warn that some of the special glasses being sold to view the Aug. 21 solar eclipse are fakes that offer little eye protection and could give users a false sense of security.
Without approved eclipse sunglasses, people and pets are at risk of blindness. Looking straight at the sun can burn the retina.
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"The sunlight has harmful ultraviolet radiation, and the problem with that is if you stare directly at the sun or an eclipse it can cause permanent damage to the eye," said Dr. Omar Punjabi, board certified ophthalmologist.
In the rush to purchase eclipse glasses and to cash in on the craze, Amazon.com and other sellers are warning about counterfeit glasses and offering refunds for those misled by false advertising.
No matter the manufacturer, safe glasses will have an imprint that says "meets the ISO 12312-2 standard," explained Steve Pfriem of the ICS lab.
Regular sunglasses are not enough, Punjabi said. It doesn't matter how dark the filter, if the glasses aren't certified, they are not safe.
At ICS Laboratories in Ohio, workers test each the filters on each pair of glasses to see how much light passes through. It is a distinction invisible to the naked eye.
"We have some pop-up vendors who are looking to play fast and loose with certification claims, testing claims," Pfriem warned. "The general public doesn't really understand what that means and more often than not those claims aren't even accurate."