Right now, you are looking at an electronic screen. Chances are, you have been looking at it for quite some time, and that you will be looking at it for some time more (if you’re not already bored, that is). As you stare at that screen in front of you, however, potentially harmful things are moving about before your very eyes, and you cannot see them. No, let me rephrase that: you can see them, but you are not aware of them. Without any further ado, let me now introduce you to blue light. Blue light, meet reader. Reader, meet blue light.
What is blue light?
Blue light is part of the visible light spectrum — what the eye can see. Vibrating within the 380 to 500 nanometres range (or 400 to 525 nanometres), it has the shortest wavelength and the highest energy. In this wavelength range, light is considered to be broad-spectrum blue light.
Light having wavelength in the general range of 400 to 450 nanometres, on the other hand, is considered high-energy visible, or narrow-spectrum blue light. A natural source of blue light is…the Sun. And then there are artificial sources. I give you LEDs and computer screen technology: together, they form the lifeline of the world. But there is a vital difference between natural and artificial sources: natural sources produce blue light of higher wavelengths, closer to the upper boundary of the wavelength range; while artificial sources produce blue light of lower wavelengths, closer to the lower boundary of the wavelength range.
Two sides of the coin: Pros and cons of blue light
Broad-spectrum blue light is essential to wakefulness, because it stimulates melanopsin receptors in the eye. This suppresses daytime melatonin, enabling wakefulness. Working in blue-free light for long periods of time disrupts circadian patterns because there is no melatonin suppression during the day, and reduced melatonin rebound at night. This problem is being felt presently by many people who have been forced to work from home due to the COVID-19 outbreak, when they had to convert restful home spaces into working environments, and found that most of the available higher CCT LEDs were too biologically disruptive to be useful. Studies have shown that increased exposure to sunlight contributes to the growth and development of eyes and vision in children, and also reduction in incidences of myopia in adolescents and early teens. Whether blue light provides any beneficial effect in improving vision and reducing chances of myopia needs to be investigated further.
Coming to the negative effects, Dr. Rahul Khurana, MD, of the American Academy of Ophthalmology claims that taking preventive action against blue light even though there is no evidence of damage could prove to be more harmful than blue light itself. He admits that too much exposure to blue light late at night from our computer screens can make it harder to go to sleep. But at the same time, he argues that the blue light exposure from screens is much less than that from the sun; and so, blue light from screens is also no more damaging than the blue light from the sun. He says that the effects of blue light are still being researched.
But other sources claim that blue light is harmful to the health of our eyes, especially our retinas. It has been claimed that since the eye is not good at blocking blue light, all of it passes easily through the cornea and lens and reaches the retina. Continued exposure to blue light over time could damage retinal cells, and induce macular degeneration. Research at the University of Toledo suggests that blue light may be able to destroy photoreceptor cells in the retina indirectly. Photoreceptor cells transmit the visual images captured on the retina to the brain via a compound known as retinal. This study focused on the effect of blue light on retinal, and the consequent effect on cultured retinal cells designed to model the function of the eye, not on actual retinal cells. Retinal is provoked by blue light, which leads to a number of chemical reactions. Now some of these reactions lead to the formation of toxic radicals which could potentially destroy photoreceptor cells. Neither retinal nor blue light by itself led to the formation of those toxic radicals: only when retinal was acted on by blue light were those radicals formed. But some experts have expressed caution at the results of this study: the researchers actually “took cells that are not from the eye, put them together with retinal in a way that doesn’t happen in the body and exposed the cells to light in a way that doesn’t happen in nature.” At the same time, a research paper by Zhao et al. has independently reported blue light to be potentially dangerous to the cornea (may cause dry eye), the lens (may cause cataract), and the retina (may cause retinal degeneration, damage of blood retinal barrier, oxidative stress injury).
Meanwhile, an article published in Harvard Health Letters in 2018 claims that “…at night, light throws the body’s biological clock – the circadian rhythm – out of whack. Sleep suffers. Worse, research shows that it may contribute to the causation of cancer, diabetes, heart disease, and obesity….[but] [t]hat’s not proof that night-time light exposure causes these conditions; nor is it clear why it could be bad for us.” It goes on to say, “While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully.” In line with this, Harvard researchers found that blue light suppressed melatonin for about twice as long as green light, and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours). Another experiment, carried out at University of Toronto, found that melatonin levels in people exposed to bright indoor light but wearing blue-light-blocking-goggles, and in people exposed to regular dim light but not wearing blue-light-blocking-goggles, was about the same. Blue light was thus concluded to be a potent suppressor of melatonin, which is known to affect the circadian rhythm considerably.
Blue light also affects us in another way: it increases the risk of developing dry eyes. Angela Bevels, OD, has this to say: “When someone is engaged on their devices, they tend to reduce the amount of blinks over time — this, in effect, causes tears to evaporate faster, leaving the cornea to dry out due to lack of tear distribution and lubrication of the corneal surface.” She goes on to claim that Meibomian Gland Dysfunction (MGD) is the leading cause of dry eye, and that this dysfunction can arise from blinking less. Zhao et al. have also mentioned dry eye in their paper as a potential problem arising from prolonged exposure to blue light: blue light disrupts our sleep patterns and can potentially cause sleep disorders; sleep disorders cause an increase in corticosteroid production, which may decrease parasympathetic nerve excitability and reduce tear secretion, thus causing dry eye.
Summing up, it has been proven, and almost all expert ophthalmologists agree on this point, that blue light disrupts the biological clocks in our bodies by regulating the secretion of melatonin. But the jury is still out debating whether blue light could be fatal to our eyes. Only time will tell. In the meantime, we should start limiting our screen-times, just in case blue light turns out to be a pain in the…well, eyes. What? You thought I would say the A-word?
The simplest precaution recommended by experts is the 20-20-20 rule: Dr. Khurana, of the AAO, recommends it, and so does Melissa Barnett, principal optometrist at the UC Davis Eye Center, and also Robert Glatter, MD, of Lenox Hill Hospital in New York City. This rule advises us to give our eyes a break from time to time: specifically, it instructs us to shift our eyes every 20 minutes, to look at something at least 20 feet away, for at least 20 seconds. There you go. Elementary, right? Besides, experts advise us to use blue-light filter while looking at computer screens for long periods of time. There is one other precaution too that experts recommend highly: they implore us to stay away from all digital devices for approximately two to three hours before we go to sleep.
So, the bottom line is: don’t panic about the problem; but don’t ignore the problem either. The problem is real, and it has the potential to injure you at least, if not harm you fatally. Stay safe. Be aware…Before I conclude this discussion, I must mention that I have consulted an extremely limited amount of resources to draw data and results from. There are innumerable other resources out there which discuss the issues tackled here much better than I have. If you come across any of them, share them with me please.
So long. Ciao!
1: “Is blue light from your cell phone, TV bad for your health?”
2: “Effects of blue light technology”
3. “Melanopsin in the circadian timing system”, Beaulé et al., 2003
4. “Should you be worried about blue light?”
5. “Effect of time spent outdoors at school on the development of myopia among children in China”, Mingguang He, Fan Xiang, Yangfa Zeng et al., 2015
6. Association between myopia, ultraviolet B radiation exposure, serum vitamin D concentrations, and genetic polymorphisms in vitamin D metabolic pathways in a multicountry European study”, Katie M. Williams et al., 2017
7: “Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness”, Chang et al., 2015
8: “Blue light has a dark side”
9: “Is blue light from your smart phone harmful to your eyes?”
10: “Blue light excited retinal intercepts cellular signalling”, Ratnayake et al., 2018, Scientific Reports, (2018) 8:10207
11: “Research progress about the effect and prevention of blue light on eyes”, Zhao et al., 2018
12: “Spectral Responses of the Human Circadian System Depend on the Irradiance and Duration of Exposure to Light”, Gooley et al., 2010
13: “Effects of Filtering Visual Short Wavelengths During Nocturnal Shiftwork on Sleep and Performance”, Rahman et al., 2013
14: “No, blue light from your smartphone is not blinding you”
15: “Differential impact in young and older individuals of blue-enriched white light on circadian physiology and alertness during sustained wakefulness”, Gabel et al., 2017
About the author: Hi! I am Subhrangshu Ghosh, freelance writer. I am also a student, presently in my third year of study in Electrical Engineering at Jadavpur University, Kolkata, India. Whenever I’m not studying (which is almost always), I either read books or write about stuff that interests me. If I have to name one thing I would want to have while I’m stranded on an island, it would be the book Meditations, by Marcus Aurelius. If I have to name one thing that I would like to do before I die, it would be to visit Iceland. If I have to name one person that I would like to meet, be it from the past or the present or the future, it would be Swami Vivekananda. For the future, I plan to be known far and wide, as an author and life-enthusiast (borrowing from Mark Manson, my idol).
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