For many decades, we’ve known that exposure to ultraviolet or UV light (nearest to blue light on the energy spectrum) has been linked to many eye diseases, most notably macular degeneration. Wearing sunglasses when you’re outside is almost second nature. But what about protecting your eyes from other types of light that we are constantly exposing our eyes to?
One of the hottest topics in eye care today both from a patient and a physician standpoint is blue light and the effects on the human body. Before we dive into that, let’s take a little crash course through basic physics and human physiology.
The visible light spectrum is exactly what it sounds like: all the light we see. The spectrum breaks apart by energy properties, or wavelengths, which our eyes and brain interpret as color. Remember Roy G. Biv? Moving from “warm colors” (red, orange, and yellow) into cool colors (blue, indigo, and violet) the wavelength shortens, translating into more energy. The higher the energy, the stronger the effects of the light. That’s why blue light gets such a bad rap.
Pre-electricity, our circadian rhythm (the natural 24-hour internal clock, also known as the sleep/wake cycle) was mainly controlled by sunlight, which encompasses all visible light. Light sources like fire do emit some blue light, but on such a minimal scale that it doesn’t impact our normal sleep/wake cycle. In the same way, more developed light sources such as halogen and incandescent light bulbs give off light across the visible spectrum, but not enough blue light to really impact our natural rhythm.
Since the beginning of the “information age” in the mid-1980s, computers have become more and more integrated into our culture. With incredible advancements in technology, they have gone from the size of a room to something that is easily portable. Artificial blue light is emitted from many now commonplace sources including laptops, TVs, tablets, eReaders, and smartphones to name a few. In our culture today, it is virtually impossible to avoid exposure to blue light from a non-natural source on a daily basis.
According to a 2018 study performed by the market research group, Nielsen, the average American spends more than 11 hours per day interacting with media platforms and more than 9 of those hours are in front of a screen. That’s 40% of your day or even more striking, 2.8 days out of the week!
By that statistic, we are on screens for more time than we sleep.
When light enters the eye, it’s just the beginning of a complex pathway through the brain. Along that pathway, there are many “gates” through which the light has to pass before it reaches the visual cortex (located at the back of the brain) for processing. The area of the visual pathway that is most impacted by blue light is the suprachiasmatic nucleus (SCN) located inside the hypothalamus. This is the center that controls our circadian rhythm.
Multiple studies have shown that light from LED screens within two hours of bedtime delay the circadian cycle and suppress melatonin, which ultimately leads to decreased restfulness during the night and impaired alertness the following morning. Further randomized trials compared a control group (normal routine) to subjects who were exposed to less blue light two hours before bedtime, who reported subjective improvement to sleep quality and mood. Additionally, individuals who have a decreased or altered circadian rhythm have a higher incidence of metabolic disorders like diabetes and depression.
“Digital eye strain” and “computer vision syndrome” are relatively new, all-encompassing terms that describe that tired feeling many of us complain about after a long day of work on the computer. Many common symptoms associated with it is a dry/watery/gritty feeling of the eyes, headaches, double vision, difficulty concentrating, etc. I don’t mean to say that these aren’t real patient complaints; they are very real, especially in the working age population. What I am saying is that what we are pinning the cause on may not have anything to do with technology. To this day, there has been no peer-reviewed study that demonstrates a direct correlation to blue light to these symptoms. That would also mean that there’s no scientific evidence that proves that computer glasses/blue-blocker tints solve this issue. So what can be done?
I usually begin conversations with my patients by asking, “Do you do a lot of computer or near work during the day/for your work?”. Across all ages, the answer is almost always, “yes”. The fact is when we do near work we blink about ⅓ as much as we would when compared to distance tasks. Not only do we blink less, but even when we do the eyes tend to incompletely close more frequently. This leads to chronic dry eye. If there is one thing I’ve learned in clinical practice it’s that there are probably 50+ ways that an individual can describe dry eye, but one of the more classic features is “fluctuation”, i.e. “sometimes it’s good, and sometimes it’s bad”. My best recommendation to people with these symptoms is to use artificial tears (please, not the kind that advertises “get the red out”) and take frequent breaks to adjust your focus to a distant target and give yourself a couple of good blinks. The American Optometric Association coined it the “20/20/20 Rule”: Every 20 minutes, take a 20-second break looking about 20 feet away.
One of the most common questions I get from my patients are my thoughts on blue light filters in the form of coatings for glasses or the yellow “computer glasses” that are commonly advertised. While I don’t see the evidence they have a big role in your helping your “computer vision syndrome” as they don’t normalize your blink rate, I do think they are especially helpful for nighttime situations that include a blue light source. There’s certainly no harm in trying them. I personally have a blue-blocker coating on my glasses that I’m wearing as I write this, and even I am starting to feel that heaviness and gritty sensation because I know I’m not blinking like I should. But since the clock just ticked past midnight, I know it will help me drift off to dreamland very shortly.
Shout out to the tech companies who have built -in a “night mode” function for their portable devices. Applications and settings to decrease blue light and replace it with warmer colors. In my opinion, are the single easiest way to help decrease your exposure to blue light during evening hours. From a scientific and clinical standpoint, I absolutely support blue light blocking technology when it comes to sleep, mood, and subsequently overall health. But, again, when it comes to “digital eye strain”, I’m not so sold on the research.