What is blue light?
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.
We usually say light but we mean visible light. Visible light is only a portion of the electromagnetic spectrum. Visible light is wavelengths between 400 –700 nm. Blue light is a portion of the visible light spectrum. It has wavelengths between 400 – 490 nm. Blue light is visible light, but it can be harmful.
Why we refer specifically to blue light?
There is an inverse relationship between the wavelength of light rays and the amount of energy they contain.
Light rays that have relatively long wavelengths have less energy. Such light rays belong to the red color. Red light has a spectrum between 600 – 700 nm.
On the other hand, light rays that have relatively short wavelengths have more energy. Such light rays belong to the blue color. So, blue light can be dangerous because it contains more energy. Compared to the rest of the visible light spectrum.
Beyond the visible blue light, it starts the invisible UV spectrum. UV has even shorter wavelengths. Therefore, the UV spectrum has even higher energy than blue light. Sunburn is mainly due to the UV spectrum.
So, we should protect our eyes from UV and blue light.
Sources of the harmful blue light
The main source of light on Earth is the Sun. As a matter of fact, the sky is blue due to the blue light spectrum. Short wavelengths of blue light diffuse more easily. So, blue light rays prevail.
Furthermore, blue light is everywhere. Every fluorescent lamp, every LED lighting, every screen, everything that produces light, produces blue light, as well.
Why do we need blue light?
Blue light isn’t something unnatural. We need blue light as it:
- regulates our natural sleep,
- regulates our wake cycles (known as circadian rhythm) (4)
- boosts alertness
- elevates mood
- makes you feel well
- prevents the occurrence and development of myopia (4)
- slows the growth of eye axis (4)
Negative effects of blue light
We function best at the natural daylight. But what about the artificial sources of blue light? Fluorescent Bulbs, led bulbs, and everything that has a screen is a source of blue light. As a result, we are being exposed to more and more sources of blue light and for longer periods of time.
Effects of night exposure to blue light
Daylight keeps a person’s internal clock aligned with the environment. Everyone has slightly different circadian rhythms, but the average length is around 24. Artificial lighting can mess circadian rhythm.
Exposure to light during night suppresses the secretion of melatonin, a hormone that influences circadian rhythms. Not only you should minimize exposure to light during night, but also you better eat foods high in melatonin, to naturally help you sleep better at night.
There’s some experimental evidence that has linked low melatonin levels with cancer. Other studies found a correlation between night light exposure, to some types of cancer, diabetes, hypertension, heart disease, and obesity (1, 2). Further research is needed, though.
Most noteworthy, the smallest source of light during the night can mess with our circadian rhythm and inhibit the natural melatonin secretion. Harvard’s researchers found that even an 8 lux night light can be bad for sleeping at night.
Short sleep has linked to increased risk for depression, diabetes, and cardiovascular problems (1).
Blue light is even worse. Blue light can suppress melatonin levels 2-fold, compared with green light (1).
Is blue light bad for your eye health?
The cornea is at the front end of the eyeball. It’s the first structure that light meets when passing through the eye. Blue light boosts inflammation of human corneal epithelial cells. Moreover, blue light can cause oxidative damage and increase the presence of free radicals. Blue light’s effects on the cornea dependents on the dose and time of exposure (4).
Lens can effectively filter short light waves, such as blue light. Lens tries to reduce retinal light damage. In order, to be more effective through time, the lens gradually darkens and turns yellow. However, when the lens has no more power to protect effectively the retina, it has to undergo a decrease in transparency or color change, which eventually leads to cataract formation. Sunlight exposure is considered to be a high-risk factor for cataracts (4).
Retina is the initial site of vision formation. Blue light can penetrate through the lens to the retina and cause retinal photochemical damage. Other studies showed that blue light can cause:
- inflammatory reactions and photoreceptor cell damage,
- degradation of retinal pigments,
- injury in retinal pigment epithelial cells.
How to protect your eye health from blue light?
Long-term exposure to blue light can cause some damage to eyesight and our overall health. With these simple everyday tips, we can minimize effects of blue light:
- Minimize the use of electronic devices at night. Protect the mechanism of melatonin secretion at night. You’ll have a longer and more quality night’s sleep. A cheap activity tracker can help you monitor the quality of your sleep.
- Eat melatonin containing foods for dinner. Melatonin from natural sources can help you sleep better.
- Try to take advantage of the natural daylight. Whenever possible open the curtains and turn off your lambs. Even some natural daylight can improve the light spectrum.
- Get regular eye exams by an eye doctor.
- Use incandescent bulbs for reading or watching TV. Incandescent bulbs emit light most similar to sunlight. So, they can provide a more natural light source to the eye. Incandescent lights provide a more natural than most fluorescent light bulbs and led lambs (1). Unfortunately, they have high energy consumption.
- Prefer to use a backlight to reduce eye strain.
- Don’t stare at a LED screen (computer, TV, or smartphone) in a completely dark room. Use a backlight instead.
- Always protect your eyes with sunglasses. Common sunglasses protect you from UV radiation, not from the blue light.
- Prefer polarized sunglasses. They tend to block efficiently short-wave blue light rays.
- Wear glasses that block blue light. They also are known as computer glasses.
- Blink frequently to keep your eyes moist.
- You should look at your computer screen slightly down. Adjust your screen and chair high.
- Hold your smartphone at a comfortable distance from your eyes. Don’t hold it very near to you.
- Apply the 20-20-20 rule. Every 20 minutes, stare an object at a distance of 20 feet (ca. 6 meters) away, for 20 seconds.
- Prefer lambs that emit a warm light. Buy LEDs with 2700 Kelvin.
- Also, the brightness of your screen should never be higher than the ambient light. Prefer warmer colors.
- Shift to warmer colors on your display. Apple and Microsoft have implemented technology that automatically makes the switch to your display at dawn. In the morning the display returns to its default color settings. There are also many apps for smartphones to do the same thing. In this way, you may protect your eyes and also have an easier time to fall asleep.
- Stop using your phone or computer at least two hours before going to bed.
- Try to sleep in a completely dark room. If you need a light source, prefer dim red light.
- Last but not least, your diet can protect your vision. Consume foods high in carotenoids and other antioxidants. For instance, lutein and zeaxanthin are the only carotenoids found in the lens. They can absorb short-wave blue light. Lutein and zeaxanthin can protect the lens’s proteins, lipids, and DNA from oxidative damage (4,5). Moringa powder is the best source of beta-carotene, lutein, and zeaxanthin. See the whole list here.
Can computer glasses protect my vision?
Researchers at the University of Toronto suggest wearing eyewear that blocks blue light is good for you. Especially during the night.
They mostly concern about melatonin secretion. They propose more advances glasses, that block out only the blue light. Avoid cheap computer glasses. Most of them have orange-tinted lenses that block blue light. The problem is that they block other colors, as well (1).