Blue Light Exposure
The LED screens of computers and portable digital devices emit a broad spectrum of visible light. Most of these light rays are harmless, but a portion of the light emitted by these screens is relatively high-energy visible light called “blue light.” Too much blue light exposure can be bad for you.
Blue light has shorter wavelengths and higher energy than other visible light rays. And laboratory research suggests certain bands of blue light may be harmful to the light-sensitive retina of the eye over time.
Blue light also plays an important role in regulating our body’s circadian rhythm. This basically is an internal clock that’s running in our brain and cycles between alertness and sleepiness at regular intervals over a 24-hour period. It’s also called our sleep/wake cycle.
Too much exposure to blue light at the wrong time of day can disrupt a person’s normal sleep/wake cycle, which can have serious health consequences.
Immediate risks from too much screen time generally occur relatively soon after repeated blue light exposure. Many of these risks are associated with circadian rhythm disruption caused by staring at digital screens well into the night, which can make it much harder to fall asleep at a normal time.
Sleep disruption can be especially problematic for children, leading to daytime drowsiness and poor performance in school because of it. Disruption of the sleep/wake cycle also can eventually lead to weight gain and obesity-related health problems.
Research has shown that people who experience disrupted 24-hour cycles of sleep and activity also are more likely to have mood disorders, lower levels of happiness and greater feelings of loneliness.
Also, an intriguing two-year study of more than 2,500 normal Los Angeles high school students found that teens who reported greater digital device use and screen time during the study were about 10 percent more likely to develop ADHD symptoms by the end of the study period. (The researchers pointed out, however, that this doesn’t prove a direct cause-and-effect relationship and more research is needed to fully understand the association between screen time and ADHD symptoms.)
Wearing glasses that filter blue light from digital screens may help reduce your child’s risk of eye problems later in life.
The simple truth is that the long-term risks of incremental blue light exposure from frequent use of digital devices is not yet known. This is because no previous generation has been exposed to comparable levels blue light from digital devices from childhood on.
It will probably take several decades before the long-term effects of extensive screen time for kids are better understood. But there is already some related research that suggests it may be wise to limit blue light exposure starting at an early age.
For example, researchers in Japan and Switzerland investigated what happened to the retinas of aging eyes from blue light exposure after cataract surgery. In the study, 79 eyes received a clear intraocular lens (IOL) that did not block blue light, and 52 eyes received a yellow IOL that blocked blue light. (Prior to cataract surgery, the retinas of all eyes were protected from blue light by the eye’s natural lens that had become clouded by cataracts.)
Two years after cataract surgery, none of the eyes that received the yellow IOL that blocked blue light showed any new or worsening signs of macular degeneration (AMD). However, among eyes that received the clear IOL that didn’t block any blue light, 15 percent of these eyes showed new or worsening signs of AMD.
The results of this study suggest that the retinas of aging eyes are more susceptible to oxidative damage caused by blue light exposure. If this is true, then it may be prudent and wise to take steps to reduce premature aging of the retina by limiting the amount of blue light exposure the eye receives throughout life.
The greatest benefit may occur when these protective measures are taken during childhood, because this is when the media of the eye (the lens in particular) are exceptionally clear and allow the greatest amount of blue light to reach the retina.