The claims associated with blue-light glasses are simple enough for an Instagram caption, and the angst they address is common enough to stick with people through the infinite scroll. According to the American Optometric Association, more than half of Americans report experiencing digital eye strain, which manifests in dry, tired eyes, usually at the end of the day. At its worst, it can give people headaches and temporarily blurred vision, which are symptoms that can feel very serious. It’s easy to assume they might be indicative of larger problems or long-term damage, and that maybe you should be safeguarding yourself.

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Despite the Instagram fad, “blue light” glasses have been around nearly as long as computers have been a part of regular life. “This first became a thing back in the late ’80s or early ’90s,” says Scott Brodie, an ophthalmologist at New York University Langone Health. The novelty of computers and the unknown repercussions of their daily use initially caused doctors and labor advocates to lobby for increased health protections for workers, Brodie explains—concerns that mirror contemporary fears about the evolving technology of our everyday lives.

Those concerns also turned out to be unfounded. “It was a tempest in a teapot. There was no excess of any eye problem in those patients. It all blew over. As far as I know, nothing of any seriousness has turned up since,” Brodie says. He points out that although these anxieties may feel recent, many people have been using computers all day for decades, and medical professionals would by now be aware of any serious eye damage caused by their use.

The makers of blue-light–blocking glasses tend to skirt around this fact in their marketing by implying a causal relationship between two things that are actually unrelated: the light emitted by digital screens and the strain we feel from looking at any one thing for too long. “Eye strain is about the disparity between the things you want to look at and the natural focusing of your eyes, and how long you do it,” says Adam Gordon, a clinical associate professor at the University of Alabama at Birmingham School of Optometry. A person could just as easily experience the symptoms of digital eye strain from reading a book for eight hours with limited breaks, but many fewer jobs require that, Gordon notes.

This neat obfuscation is made easier by the fact that few consumers know what blue light actually is or where it comes from, except that it’s associated with digital screens. But as Gordon points out, screens are far from the only source. “There are studies that have shown that sunlight, just standing outdoors in the daytime, is like 200 times more intense an exposure to blue light than any screen for eight or 10 hours a day,” he says. If blue light was the cause of eye strain, it would be far worse in those who work outdoors than in office dwellers or heavy smartphone users.