For as long as we’ve been using handheld devices to go online (and probably longer), many of us have had our eyes riveted to bright screens late into the evening. As optometrists, we can’t approve of this bedtime ritual. Screens emit blue light, and that can throw off our internal clocks and possibly affect our eye health.
All of the colors we perceive are on the visible light spectrum, just a tiny sliver of the electromagnetic spectrum. Below visible light is infrared radiation and above blue and violet is ultraviolet radiation. Blue and violet are the highest-energy light waves we can see. (Fun fact: the reason the sky looks blue to us is that blue light scatters more easily than other colors. It’s called Rayleigh scattering.)
In all of human history, the only source of blue light was the sun — up until the last few decades. Our bodies interpret blue light as the signal that it’s time to be awake, so we tend to feel more attentive, remember things more easily, feel better, and have faster reactions during the day. As soon as the sun sets, the lack of blue light signals our bodies that it’s time to wind down for sleep. We aren’t biologically programmed to know the difference between the sun and artificial blue light.
This means that when we light up a screen before bed, we’re blasting our brains with a signal that it’s still time to be awake. Our brains respond by not releasing neurotransmitters that help us sleep, like melatonin. It then takes us longer to fall asleep and we might not enjoy very high-quality sleep. That contributes to a cycle of sleep deprivation and the negative health effects that come with it.
We can minimize these sleep issues by putting our devices away in the last hour before bed, or at least by switching them to night mode so that they don’t emit any blue light and trigger those subconscious signals in our brains.
Many optometrists have been concerned that blue light could be close enough to UV radiation that it might cause similar damage to our eyes, with effects like an increased risk of age-related macular degeneration. However, while our screens give off enough blue light to mess with our sleep schedules, they emit very little compared to the sun, and they don’t emit UV light at all.
The main concern with blue light and eye health is digital eye strain. Spending hours a day staring at a bright screen can make our eyes ache or have difficulty focusing. We could end up having more frequent headaches or struggle to get through our work. We can use tools like screen filters and computer glasses to help block blue light, but a simple trick that can help a lot is the 20-20-20 rule. Every 20 minutes of screentime, take a 20-second break to focus on something at least 20 feet away.
If you’ve experienced symptoms of eye strain during or after using bright screens, we’re happy to discuss it with you and answer your questions. We want to give our patients all the information they need to make smart choices for their eye health.