You’ve heard it before, we know: All that “screen time” isn’t good for our eyes or our bodies. But, real talk -- does it matter? How harmful could any of this be, really?
We talked to an expert to get some answers.
VSP Vision Care provider Dr. Gary Morgan helped us answer the following questions. Some responses have been lightly edited for length or clarity.
Q: What is blue light, anyway?
A: We are surrounded by waves: radio waves, ultraviolet waves, infrared waves and light waves. Waves come in lengths, known as wavelengths. (That’s the original name, right?). The thing about wavelengths is, the shorter the wavelength, the higher the energy, which translates into higher potential to cause damage to living things. UV light has short wavelengths -- so short that we can see it. But its high energy has the potential to cause short-term damage to our skin, for example, a sunburn, and long-term damage, such as melanoma. Radio waves, on the other hand, are long wavelength with low energy. Since mobile phones use radio wavelengths, the signal can drop if you get into an elevator while talking.
Stick with us now: Visible light wavelengths can be identified by color, with the shortest wavelengths having the coolest color, so blue light is short wavelength visible light. In fact, blue light is next to UV light on the electromagnetic spectrum; UV light ranges from 100-400 nanometers, and visible light from 400-750 nanometers. Blue light is defined as containing wavelengths from 400-500 nanometers. Therefore, blue light has the shortest wavelength and the highest energy (of visible light), giving it the greatest potential to cause damage, especially to the interior of the eye, the retina.
Q: When we talk about blue light, is it all the same?
A: It all goes back to wavelength. Remember, blue light is defined as 400-500 nanometers. The sun, smartphones, tablets, televisions and energy-efficient lightbulbs all emit 400-500 nanometer light. However, the intensity of the blue light differs by source. Sunlight is 100 times more intense than light coming off your iPhone. People don’t typically stare at the sun for eight hours per day, but they do look at their digital devices for that long -- or longer.
Q: So, what does that mean for our eye health?
A: There are still many unknowns. It’s not yet clear at what intensity and duration of exposure will blue light cause retinal damage. Unfortunately, aside from acute damage, chronic exposure data is not available. Consider that the first iPhone became available in 2007 and iPad in 2010, yet in 2014, those devices outnumbered people on Earth.
Here’s what we do know: Age-related macular degeneration is the leading cause of blindness for people 60 years or older in developed nations. One factor driving retinal damage is cumulative lifetime exposure to blue light. Something called the Beaver Dam Eye Study was a retrospective study of people in their 70s and 80s, and it looked at sunlight exposure when those people were in their teens and 30s.
-- Scroll down all the way to the bottom, for ways to minimize the effects of blue light. --
The average time of sunlight exposure was two hours per day. However, for those who had exposure of five hours per day, they had an onset of age-related macular degeneration 10 years earlier, doubling their chances of blindness.
Sunlight is more intense than digital device screens, and in the Beaver Dam study, three hours longer duration of exposure per day made a difference in retinal damage. As we are only 11 years into using our eyes the way they have never been used in the course of human history, it is too early to tell if six, eight, 10 or more hours per day of screen usage will bring about retinal damage.
Q: Do you get the feeling people are worried about blue light? Are eye patients requesting blue light protection on their frames? Does it seem like more of a concern lately, compared to even a few years ago?
A: I gave my first lecture on blue light in 2010. The doctors in the audience probably thought I wore a tinfoil hat at home -- blue light was definitely not a mainstream topic. In 2012, the first blue light-filtering spectacle lens was introduced. In 2017, there were close to 100 different blue light-filtering lenses available.
As doctors took notice of blue light, the mainstream media did as well, and reports started trickling out. Today, there is certainly blue light awareness among my patients, and yes, many do come in requesting blue light protective lenses. Interestingly, a friend of mine sent me a text [the very morning the doctor was answering these questions] to tell me that he was listening to “The Howard Stern Show,” and they had just talked about a blue light study for 20 minutes. Mainstream indeed!
Q: Would you consider the effects of blue light to be a health concern? Playing on our phones before bed, for example -- that can lead to problems with sleep, right?
A: Phones emit blue light in the 400-500 nanometer range. The wavelengths most affecting sleep are 460-490 nanometers. There are specialized cells in our retina called intrinsically photosensitive retinal ganglion cells, or ipRGCs, that are most sensitive to these wavelengths. During the day, blue light from the sun and electronics are incident on these ipRGCs, which send a signal to the brain, to our body’s internal clock. That signals the pineal gland to suppress melatonin (our sleep hormone), which promotes wakefulness. In the absence of blue light, ipRGCs signal something inside the brain to allow melatonin secretion from the pineal gland, which promotes sleep.
[Still with us? This next part is important.]
Blue light, especially wavelengths from 460-490 nanometers, encountered after dark, as from mobile phones, suppresses melatonin. This diminishes the quantity and quality of sleep, as melatonin secretion is delayed and does not reach the same peak levels as when blue light is not encountered after dark. It’s been well-documented that sleep disruption has adverse health consequences and has been linked to obesity, diabetes, heart disease, depression, stroke and cancer.
Q: Any concerns involving handing over tablets or smartphones to children?
A: The same issues (noted above) apply to children.
Viewing digital devices after dark delays the onset of melatonin secretion and thus sleep, diminishing quality and quantity. Also, getting woken up by text messages further degrades the normal sleep-wake cycle (circadian rhythm). In children, short- and long-term sleep deprivation enhanced the following: appetite, obesity, reduced insulin sensitivity, greater Type 2 diabetes risk, hyperactivity, diminished ability to focus attention, mood swings, poorer academic performance, impaired immunity, attentional failures, slower reaction times, degraded memory consolidation, anxiety and a depressed mood. This adverse effect on sleep and the accompanying symptoms mimic those of attention deficit hyperactivity disorder, or ADHD.
Q: Are kids and teenagers more sensitive to lights at night than adults are?
A: They are not more sensitive from a physiologic perspective, but they might be from the angle of peer pressure. Perhaps they are inclined to look at their devices well into the night and perhaps through the night to not be left out socially.
Q: Is it harmful even just to be up at night? Does that throw our internal body clocks off? What about people who work second- and third-shifts?
A: It’s not the being up, it is the light exposure at night, specifically blue light. The World Health Organization has added night-shift work to its list of known and probable carcinogens.
Graham Media Group 2018