Sources of blue light include the sun, digital screens (TVs, computers, laptops, smart phones and tablets), electronic devices, and fluorescent and LED lighting.

Natural blue light versus artificial blue light

Blue light is actually everywhere. When outside, light from the sun travels through the atmosphere. The shorter, high energy blue wavelengths collide with the air molecules causing blue light to scatter everywhere.  This is what makes the sky look blue. In its natural form, your body uses blue light from the sun to regulate your natural sleep and wake cycles.  This is known as your circadian rhythm.  Blue light also helps boost alertness, heighten reaction times, elevate moods, and increase the feeling of well being. Artificial sources of blue light include electronic devices such as cell phones and laptop computers, as well as energy-efficient fluorescent bulbs and LED lights.

Why should we be concerned about blue light exposure?

Blue light waves are the among the shortest, highest energy wavelengths in the visible light spectrum.  Because they are shorter, these "Blue" or High Energy Visible (HEV) wavelengths flicker more easily than longer, weaker wavelengths. This kind of flickering creates a glare that can reduce visual contrast and affect sharpness and clarity. 

This flickering and glaring may be one of the reasons for eyestrain, headaches, physical and mental fatigue caused by many hours sitting in front of a computer screen or other electronic device.  

Our eyes' natural filters do not provide sufficient protection against  blue light rays from the sun, let alone the blue light emanating from these devices or from blue light emitted from fluorescent-light tubes. Prolonged exposure to blue light may cause retinal damage and contribute to age-related macular degeneration, which can lead to loss of vision.