What is blue light?
Light that the human eye is able to see is known as visible light, which consists of wavelengths of varying lengths that are seen as different colours by the human eye. Blue light has a fairly short wavelength and is found close to the invisible, but harmful, UV rays on the light spectrum.
(AMD refers to the portion on the light spectrum that is deemed to be harmful to the eyes and can lead to diseases such as cataracts and age-related macular degeneration (AMD).)
In 1998 a new type of photoreceptor was discovered in the eye, identified as melanopsin retinal ganglion cells, which provide signals to various brain regions. One of these regions is the suprachiasmatic nucleus, which is regarded as the brain’s master clock. Further research has shown that these photoreceptors are especially sensitive to blue light, in turn affecting our circadian rhythm. (Internal clock)
Light follows two pathways in the eye – the primary optic tract that governs visual perception and responses – and the retinohypothalamic tract that governs circadian, endocrine and neurobehavioural functions. The retinohypothalamic tract is most sensitive to blue light stimulation. (Source: Environmental Health Perspectives)
Applications of blue light:
Blue light has many applications due to its specific properties. The glare and brightness that are perceived with light perception are functions of wavelength. The short wavelength of blue light appears relatively bright to human eyes, making this one of the most energy efficient colours of light to produce. For example, the “daylight” versions of compact fluorescent lamps (CFL’s) and LED lamps have a blue orientated colour balance and are more energy efficient. (The bluer the CFL the more energy efficient)
Dentists utilize blue curing lights to harden amalgam material. In the automotive industry the high-intensity discharge headlamps found in some vehicles emits a bluish light that increases visibility while using less energy than halogen headlamps. The downside is increased glare for drivers in oncoming traffic.
The major application of blue light is in the electronic devices most of us use on a daily basis – mobile phones, tablets, lap top computers – and it has drastically increased our exposure to blue light.
The effect of blue light on the human body:
• Experiments have indicated that blue wavelengths suppress the delta brainwaves that are associated with sleep, while boosting the alpha brainwaves that are associated with alertness.
• The light from our electronic devices has a higher concentration of blue light than natural light and affects the levels of melatonin – the sleep inducing hormone – more than any other wavelength.
• Studies have shown that exposure to blue light a couple of hours before bedtime suppresses the production of melatonin and delays deep sleep in the REM phase significantly. While low levels of melatonin is present during the day, it starts being released a few hours before bedtime and reaches its peak in the middle of the night.
• Changes in sleeping patterns can shift or reset the body’s circadian rhythm – the body’s natural clock. These shifts can have detrimental effects on our health, as it not only controls wakefulness, but also “individual clocks” that dictate function in the body’s organs.
• In a study on the effects of reading on a light-emitting device compared to reading a printed book before bedtime, the participants reading on light-emitting devices took longer to fall asleep, were more alert, and had less REM sleep. After an 8 hour sleep, they were sleepier and took longer to wake up.
• As a matter of interest, the results of this study have prompted NASA to contact the scientists with a view of applying the findings to flights in space. The International Space Station orbits Earth every 90 minutes and astronauts see the sun rise and set each time. This has led to NASA implementing a new lighting system to improve the sleeping patterns of astronauts.
• Too much exposure from the blue light originating from electronic devices may have a damaging effect on the eyes. Blue light is the highest energy wavelength of visible light and can penetrate past the natural filters in the eye to the back of the eye, where it may cause cumulative damage and lead to eye disease such as macular degeneration. Children are more at risk as their eyes are still developing and don’t have all of the protective pigments in their eyes yet.
• Looking at the screens of electronic devices for extended periods of time can lead to digital eye strain that results from not blinking enough. Blinking helps to keep the eyes lubricated.
How to minimize the effects of blue light:
To reduce the effects of digital eye strain, one should get into the habit of consciously blinking more when looking at electronic devices. It also helps to look away from the screen every 20 minutes or so and to focus at an object about 5 meters away for at least 20 seconds.
An eye care practitioner can prescribe lenses that filter out blue light.
Cut back on the use of, or completely avoid, electronic devices for at least an hour or more before bedtime.
Sources:
Is blue light exposure really a concern? Updated 7 March 2018. Verywell Health. (www.verywell.com)
What is in a colour? The unique human health of blue light. Published January 2010 in Environmental Health Perspectives. US National Library of Medicine, National Institutes of Health. (www.ncbi.nlm.nih.gov)
How to protect your eyes from the negative effects of digital devices and blue light. Published 24 July 2014. The Huffington Post. (www.huffingtonpost.com)
Q&A: Why is blue light before bedtime bad for sleep? Two neuroscientists discuss how blue light negatively affects health and sleep patterns. Published 1 September 2015. Scientific American. (www.scientificamerican.com)
HEALTH INSIGHT
MAY 2018
