Best answer: Blue light filtering screen protectors use a special coating that blocks light in the 380-500 nanometer range. Electronics like phones use LED or OLED panels that emit light in this range to help brightness and improve clarity, but they can also reach the rear of the retina. Some studies claim this can be harmful, but so far, there is no conclusive proof of this. What scientists and doctors do agree on, though, is that blue light can make it harder for us to get to sleep. To help with that, you'll need to filter that blue light.