In recent years, there has been a push in building awareness among the general public with regards to blue light. Many lens companies have pushed for blue light filters on their lenses to filter out blue light. Is this just a marketing gimmick to push out new products? Or is there a legitimate reason why this trend exists today?

What is blue light?

Our main source of light from the sun, sunlight, is a spectrum consisting of varying colours namely, red, orange, yellow, green, blue, indigo and violet. By combining all these colours, it becomes white light, which we use to see and go about our day. Each individual colour has its own wavelength and energy, hence allowing us to distinguish them. It is because of these individual properties that allow us to see the different colours of the rainbow after a rainy day.

There are seven colours of light, so why is blue light being singled out?

Blue light, having the shortest wavelength, has the most energy and therefore can potentially cause the most damage to cells.

Research has shown that blue light plays a role in managing our biological clock, known as the circadian rhythm. The circadian rhythm is regulated by the hormone, melatonin. Melatonin is responsible for making us feel sleepy, the lesser melatonin, the more awake we are. Blue light stimulates a part of our brains to suppress the production of melatonin which in turns help us stay awake during daytime.

Artificial lighting and digital devices help us stay illuminated and awake even after the sun has set. It is found that these light sources are more concentrated in blue light than any other sources. With the increasing prevalence of digital devices and the shift to energy efficient artificial lighting, our exposure to blue light increases. 

Is blue light harmful?

There have been claims that blue light causes retina damage. Animal studies have shown that blue light can cause damage to rabbit and mouse retina through various mechanisms. It is extrapolated from these research data and assumed that excess quantities of blue light may be detrimental to the human retina as well. However, there is no conclusive evidence from research that documents human retina damage by blue light. For this reason, we tend to err on the side of caution and try to limit excessive blue light exposure to our eyes.

It is unscientific to equate all blue light as harmful. Some blue light is required to regulate normal circadian rhythms and prevent development of myopia. Blue-light deprivation has also been shown to be associated with depression-like changes in the brain. As with most things in life, blue light exposure should be kept within moderate amounts. Most normal digital displays present minimal risks as the blue light emittance is within standard acceptable range; however this is only a conclusion with respect to short-term exposure. If long-term exposure is necessary, additional anti-blue light measures would be encouraged.

Although we do not have conclusive proof of retinal damage by blue light, research has shown that exposure to blue light can disrupt the normal sleep cycle. Having insufficient rest can lead to a myriad of health conditions such as increased risk of diabetes, heart disease and obesity. Therefore, it is recommended to reduce the use of digital devices especially two to three hours before you go to bed for better sleep.

How effective are currently available blue-light-blocking lenses in reducing the effects of blue light?

Blue-light blocking lenses block between 20 to 70% of blue light, depending on the quality of the lens. As mentioned before, we do need a certain amount of blue light for health reasons and we should not aim to filter out 100% of blue light. Such blue light lenses are helpful in reducing the amount of blue light exposure especially for people who are getting prolonged exposure to digital screens (staring at their screens for the whole day). It is less critical for people who have little to moderate exposure to digital screens. 

Other than reducing screen time and using blue-light-blocking lenses, can we do anything else to reduce the effects of blue light?

We can use blue-light blocking filters that are put in front of our computer screens or phone screens. Alternatively, many devices now have a night mode setting that minimizes the amount of blue light in the evenings. When these settings kick in, the colours on screen often changes to a warmer tone – usually a yellowish orange shift. This shift is dependent on how aggressive the blue light filtering is determined by your settings. In this way, we are reducing the blue light coming from our digital screens while maintaining good exposure to natural blue light from the sun.

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