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What is Blue Light

Most people are aware that sunlight contains visible light rays and also invisible ultraviolet rays that can tan or burn the skin. But what many don't know is that the visible light emitted by the sun comprises a range of different-colored light rays that contain different amounts of energy.

Visible light is much more complex than you might think.

Stepping outdoors into sunlight; flipping on a wall switch indoors; turning on your computer, phone or other digital device — all of these things result in your eyes being exposed to a variety of visible (and sometimes invisible) light rays that can have a range of effects.

Blue light

Sunlight contains red, orange, yellow, green and blue light rays and many shades of each of these colors, depending on the energy and wavelength of the individual rays (also called electromagnetic radiation). Combined, this spectrum of colored light rays creates what we call "white light" or sunlight.

There is an inverse relationship between the wavelength of light rays and the amount of energy they contain. Light rays that have relatively long wavelengths contain less energy, and those with short wavelengths have more energy.

Rays on the blue end of the spectrum have shorter wavelengths and more energy. Rays on the red end of the visible light spectrum have longer wavelengths and, therefore, less energy.

Like ultraviolet radiation, visible blue light — the portion of the visible light spectrum with the shortest wavelengths and highest energy — has both benefits and dangers. Here are important things you should know about blue light:

girl checks out her phone blue light

 

HEV light rays make the sky look blue.

The short-wavelength, high-energy light rays on the blue end of the visible light spectrum scatter more easily than other visible light rays when they strike air and water molecules in the atmosphere. The higher degree of scattering of these rays is what makes a cloudless sky look blue.

Blue light is everywhere.

Sunlight is the main source of blue light, and being outdoors during daylight is where most of us get most of our exposure to it. But there are also many man-made, indoor sources of blue light, including fluorescent and LED lighting and flat-screen televisions.

Most notably, the display screens of computers, electronic notebooks, smartphones and other digital devices emit significant amounts of blue light. The amount of HEV light these devices emit is only a fraction of that emitted by the sun. But the amount of time people spend using these devices and the proximity of these screens to the user's face have many eye doctors and other health care professionals concerned about possible long-term effects of blue light on eye health.

Blue light contributes to digital eye strain.

Because short-wavelength, high energy blue light scatters more easily than other visible light, it is not as easily focused. When you're looking at computer screens and other digital devices that emit significant amounts of blue light, this unfocused visual "noise" reduces contrast and can contribute to digital eye strain.

Blue light exposure may increase the risk of macular degeneration.

The fact that blue light penetrates all the way to the retina (the inner lining of the back of the eye) is important, because laboratory studies have shown that too much exposure to blue light can damage light-sensitive cells in the retina. This causes changes that resemble those of macular degeneration, which can lead to permanent vision loss.

Although more research is needed to determine how much natural and man-made blue light is "too much blue light" for the retina, many eye care providers are concerned that the added blue light exposure from computer screens, smartphones and other digital devices might increase a person's risk of macular degeneration later in life.

The eye is not very good at blocking blue light.

Anterior structures of the adult human eye (the cornea and lens) are very effective at blocking UV rays from reaching the light-sensitive retina at the back of the eyeball. In fact, less than one percent of UV radiation from the sun reaches the retina, even if you aren't wearing sunglasses.

(Keep in mind, though, that sunglasses that block 100 percent of UV are essential to protect these and other parts of the eye from damage that could lead to cataracts, snow blindness, a pinguecula and/or pterygium, and even cancer.)

On the other hand, virtually all visible blue light passes through the cornea and lens and reaches the retina.

User using blue light filter on tablet


If you are using your phone constantly — especially if you use it primarily for texting, e-mailing and web browsing — a convenient way to reduce your blue light exposure is to use a blue light filter.

Digital electronic devices emit blue light that can cause eye strain and may lead to eye problems over time.

These filters are available for smartphones, tablets, and computer screens and prevent significant amounts of blue light emitted from these devices from reaching your eyes without affecting the visibility of the display. Some are made with thin tempered glass that also protects your device's screen from scratches.

Ask your eye doctor about which type of vision correction and lens features best suit your needs for viewing your computer and other digital devices and protecting your eyes from blue light.