The manufacturing and use of low emitting diode (LED) lighting has undergone rapid technological development in recent years, taking the world by storm. The LED light sources are small and bright, but also very energy efficient, using up to 95% less energy than traditional light sources. LEDs light up the screens of our TV’s and electronic devices, our homes, shops, and even used in creatively designed and highly visible vehicle lights.
How do these tiny lights in electronic devices affect our eyes, especially those of us who spend long hours of screen-time on a daily basis? Eye care specialists and other health care professionals have over time expressed their concerns about the long term effect of the blue light emitted by these devices, on our eyes.
Harvard Medical School, however, recently stated that there is no scientific evidence that the lights from electronic devices are harmful to the retina or any other part of the eye. In line with Harvard’s findings, the Prevent Blindness eye health and safety organization in the USA says that digital screens give little or no harmful radiation and the levels of radiation are below levels that can cause eye damage.
Where do LED lights fit into the colour spectrum?
Light consists of electronic particles that travel in waves and these waves emit energy. To fully understand the impact of LED’s on the eyes, it is important to determine whether their specific wavelength in the colour spectrum poses a threat to our eyes. Sunlight contains many different shades of the primary colours – ranging from red, orange, yellow, green to blue – depending on the energy and wavelength of the individual rays of sunshine. This combined spectrum of coloured rays creates what we perceive as “white light”, or sunlight. The human eye cannot see the full spectrum of light from the sun. The range of sunlight that we are able to see is known as “visible light”.
The electromagnetic rays on the red end of the visible colour spectrum have longer wavelengths and less energy, while rays on the opposite blue end of the visible colour spectrum have shorter wavelengths and more energy. The colour spectrum continues on both the opposing red and blue ends of the spectrum, but are no longer visible to our eyes.
An example in this regard is infrared rays on the red end of the spectrum which are warming, but no longer visible. (Infrared lamps used for heating purposes are designed to also emit visible red light so we can see when they are switched on.) On the blue end of the spectrum, the invisible blue rays have the shortest wavelengths and highest energy and are known as blue-violet light. An example is ultraviolet radiation, which is harmful to our eyes and skin.
Ultraviolet light ranges from UVC that is below 286 nm and effectively filtered by the earth’s ozone layer; UVB from 286-320nm which causes sunburn; and UVA from 320-400nm which is the most damaging part of the UV spectrum to the eyes. (Nm stands for nanometer, which is one billionth of a meter.) Blue light varies in the wavelengths 400-500nm and the light emitted from LED and fluorescent lamps form part of visible blue light.
The advantage of LEDs as a source of light is that its wavelength is around the 470nm mark, away from the danger zone below 400nm. LED lighting is also deemed to be less harmful to the eyes than fluorescent lighting.
Sources of visible blue light.
Being outdoors during the day means that sunlight would be the main source of blue light, although it is not visible as such, as we see all the colours together as sunlight/white light.
Artificial sources of blue light include energy efficient fluorescent bulbs and LED lights, flat-screen televisions and the screens of electronic devices such as computers, smartphones, electronic notebooks and other digital devices.
The screen of a full colour electronic device have tiny individually controlled red, green and blue LEDs that are packed tightly together to provide a picture in full colour. Bright white-light LEDs provide back-light to the screens and is the biggest source of blue light from these devices, but as Harvard indicated, the amount is not harmful to the eyes.
LEDs (light-emitting diodes) consist of a semiconductor chip positioned on a reflective surface, and light is produced when electricity runs through the semiconductor. White light LEDs are made by applying a yellow phosphor coating to blue LEDs.
As a matter of interest, the short wavelength and high energy of blue rays from the sun tend to scatter more easily than other rays. The blue rays tend to scatter when colliding with water and air molecules in the atmosphere, resulting in the blue colour of the sky above.
Effects of blue light:
On the eyes: As blue light can actually penetrate the retina, laboratory studies have shown that too much direct exposure can damage light-sensitive cells in the retina. This has resulted in concerns about the long term effect of exposure to blue light from electronic devices. According to Harvard, high enough doses of blue light are likely to cause damage when absorbed by various cells in the body, but the amount of blue light that is emitted from electronic devices are low enough not to be harmful.
High intensity blue light is potentially harmful to the eyes as it is very bright, for example from direct exposure to “military grade” flashlights. The golden rule is not to look directly into any source of blue light that is extremely bright, similar to not looking directly into the sun.
A fairly new medical issue is called digital eyestrain and it describes the conditions that result from spending the majority of our waking hours staring at a digital screen. Symptoms include headaches, blurry vision, irritated or dry eyes, neck and back pain.
On sleeping patterns: While blue light from LEDs in electronic screens may not pose a hazard to the retina, it affects the body’s circadian clock (the internal biological clock) and sleeping patterns. Blue light from the sun helps to regulate the body’s natural sleep and wake cycles. Exposure to blue light during the day helps to maintain the natural circadian rhythm of wakefulness during daylight, but exposure to blue light at night can disrupt sleeping patterns. This is due to blue light inhibiting the release of melatonin from the pineal gland, which is the hormone that encourages sleep when it is dark.
It is advisable to limit the use of all electronic devices for a few hours before going to bed.
Sources:
Will blue light from electronic devices increase my risk of macular degeneration and blindness? Published online 8 April 2019. Harvard Medical School. (www.health.harvard.edu)
Blue light: It is both bad and good for you. Published online and updated November 2017. All About Vision. (www.allaboutvision.com)
Ultra-violet and blue-light aggravate macular degeneration. Published online. American Macular Degeneration Foundation. (www.macular.org)
Digital devices and your eyes. Published online and updated 4 September 2016. Prevent Blindness. (www.preventblindness.org)
LED vs traditional lighting: Its effect on the human eye. Published online and updated 5 October 2015. LED Source. (www.ledsource.com)
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