Blue Light and Screens

What screens emit and how blue light affects the eye

Overview

Blue light is visible light at the short wavelength end of the spectrum, roughly 400 to 500 nanometers. Sunlight is by far the largest source of exposure, while LED lighting and digital screens emit much smaller amounts. High intensity blue light can damage the retina through photochemical mechanisms, a hazard demonstrated in laboratory studies and in situations such as staring at the sun, but the levels emitted by consumer screens are far below established exposure limits, and evidence that screen use causes retinal disease is lacking. Discomfort associated with screens, known as digital eye strain, is attributed mainly to reduced blinking and sustained near focus rather than to blue light. Blue light filtering spectacle lenses are widely marketed, but systematic reviews have not found that they meaningfully reduce eye strain. Blue light does have important biological effects through melanopsin containing retinal ganglion cells, which help regulate the circadian rhythm and the release of melatonin, so evening exposure to bright light, including from screens, has been studied for its effects on sleep timing.