Most people know that sunlight is comprised of visible light rays as well as invisible ultraviolet rays that can cause sunburn. However, many don’t realize that the visible light of the sun is comprised of a range of rainbow-colored light frequencies. These various colors of light emit different levels of energy.
Sunlight contains all the colors of the rainbow, red, orange, yellow, green and blue light. When combined, this spectrum of rainbow light makes up what we know as “white light”. Light rays with a longer wavelength have less energy, and light colors with shorter wavelengths have more energy. Red light rays have longer wavelengths and less energy. However, blue light rays have a shorter wavelength and, therefore, more energy. Beyond blue light is what we know as ultraviolet (UV) radiation.
Blue light, like ultraviolet radiation, has both dangers and benefits. While the sun is the primary source of blue light, man-made sources of indoor blue light have raised concerns. These include LED and fluorescent lights, computer, tablet, and smartphone screens, as well as flat-screen televisions.
The amount of blue light emitted by these devices only makes up only a tiny fraction compared to that emitted by the sun. However, the amount of time many people spend on these electronic devices has many health care professionals worried; the long-term effects of excessive blue light may have on eye health could be devastating.
The eye’s lens and cornea are quite effective at blocking harmful UV rays from reaching the retina at the back of the eye. As a matter of fact, less than 1% of the UV rays from the sun reach the retina, even without sunglasses. However, nearly all of the blue light rays pass through the lens and cornea, reaching the retina.
This is important, since scientific studies have shown that over-exposure to blue light can damage the retina. Excess blue light can cause damage similar to macular degeneration, which can cause a permanent loss of vision. While more research is necessary, many eye doctors are concerned that excess exposure to blue from smartphones and computer screens may increase the risk of macular degeneration.
Natural levels of blue light are essential to our well being, in fact, blue light is used to treat SAD (seasonal affective disorder). Likewise, blue light is essential to our circadian rhythm; however, too much blue light after sunset can disrupt this circadian rhythm, potentially causing insomnia and daytime fatigue.
While most of us must spend time on the computer daily, it’s best to limit your screen time. Likewise, you can put a “blue filter” over your computer or smartphone screen, and wear yellow-tinted computer glasses to help preserve our vision.