They use a device called a spectrophotometer to measure the exact percentage of light that passes through a lens at every single wavelength. Do blue light glasses actually work? Don't rely on advertisements; look at the spectrometer test data. Goiteia tested four colors of blue. The most reliable at-home test is the screen test: find a blue color swatch online, hold your glasses between your eyes and the screen, and look for a significant dimming or color shift in the blue area. If you see a change, your lenses are filtering blue light. A spectrometer is a device that's able to measure the entire visible light spectrum all the way from 380nm violet light to 780 nm deep red light, and everything in. Blue light blocking glasses employ two main methods to filter out a portion of the high-energy blue-violet light spectrum, which ranges from approximately 400 to 450 nanometers.
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