Sunlight is the main source of blue light, and 38 outdoors during daylight is where most of us get most of our exposure 39 it. But there are also many man-made, indoor sources of blue light, 40 fluorescent and LED lighting and flat-screen televisions. Most notably, the display screens of computers, electronic notebooks, smartphones and other digital devices 41 significant amounts of blue light. The amount of time people spend using these devices and the proximity of these screens to the user's face have many health care professionals 42 possible long-term effects of blue light on eye health.