Between our TVs and computers, many of us spend hours upon hours every day staring at screens. Throw a smartphone into the mix and it won't be long before your eyes have simply had too much. In fact, I'll be the first to admit that I've tired out my own eyes plenty of times just scrolling through my Instagram feed. "Extended use of digital devices and exposure to screens can cause digital eye strain," Dr. Howard Purcell, an optometrist, Fellow of the American Academy of Optometry, and the Senior Vice President of Customer Development at at Essilor, told me. "Symptoms can include blurry vision, trouble focusing on one thing, red, tired, or dry eyes, as well as headaches." 

This is because our devices emit low levels of harmful blue light, which Dr. Purcell says that studies suggest can change the way our pupils react to light, causing light sensitivity and strain around and behind the eyes. "Think of the eyes like any muscle. You have six muscles that move each eye, and one muscle that focuses it," he said. "Overuse can certainly cause your eye to fatigue."

If you're going to be concentrating on any screen for a long time, Dr. Purcell suggests trying the 20/20/20 rule. "The goal is to take a break every 20 minutes, for 20 seconds, and look at something that's at least 20 feet away."