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Recently, my brother mentioned that since he bought new prescription glasses with blue light filter, his sleep has been much better. He wears glasses mainly to read the screen (computer and smartphone) while working during the day. So I am very interested, but a little skeptical: Will using blue light filter glasses during the day affect his sleep quality? Before deciding whether these glasses can also help me, it seems a good question to ask experts how, when and why blue light will affect us.

Visible light includes a short wavelength, which is hidden in the electromagnetic radiation spectrum. The wavelengths of visible light captured by our eyes are converted into white light by our brains.

You may remember to use a prism to bend the wavelengths of white light into rainbow colors. At one end of this rainbow, the blue light gradually turned purple. Sunlight has a lot of light at all visible wavelengths.

Measured in nanometers (nm), the visible light wavelength range is 400 to 700 nm. The wavelength of blue light is between approximately 450 and 495 nm. Different blue light wavelength segments have different effects on our body, including sleep and alertness.

Dr. Steven Rockley, a neuroscientist at the Department of Sleep and Circadian Disorders at Harvard University’s Brigham and Women’s Hospital, said that in addition to helping us see things, light also has non-visual effects on the body.

The 24-hour biological clock in the brain regulates sleep and wake cycles, hormonal activity, diet and digestion, and other important processes in the body. "Special photoreceptors in the eyes detect light to control our circadian rhythm," he said. These cells contain a non-visual photosensitive pigment called melanopsin, which is most sensitive to 480 nm light at the blue-green end of the visible spectrum. Other visual photoreceptors called cones allow us to see blue-violet light with a shorter wavelength of about 450 nm.

The blue-rich light during the day is desirable because it helps to synchronize our biological clock with the 24 hours a day. Therefore, regular exposure to light and dark cycles is essential for achieving and maintaining good sleep.

Stimulation of blue light from certain wavelengths can help us stay alert, whether it comes from natural light sources such as the sun during the day, or from electronic devices that emit blue light. Although stimulation helps during the day, it interferes with sleep at night. Exposure to blue light at night—for example, playing a TV series on a laptop before going to bed—stimulates melanopsin-containing cells and reminds the brain to think it is daytime. This will make it more difficult for you to fall asleep and may affect the quality of your sleep.

Although a recent systematic review indicated that anti-blue glasses may help patients with insomnia, Dr. Lockley said that detailed information about these studies is not sufficient to draw this conclusion. Most commercially available blue light filter glasses and special coatings added to prescription lenses are not standardized. Therefore, you cannot know which wavelengths are blocked, and whether this only affects visual functions, or important non-visual functions, such as alertness and the biological clock. In addition, the duration, duration, and nature of night light in these research abstracts are also unclear.

If you want to block the irritating blue light that can interfere with sleep, avoid using the screen as much as possible after dusk-especially within two to three hours before bedtime. You can also try to use computer software that reduces the amount of blue light emitted. Examples include Night Shift (available on Apple devices) or f.lux, which can be downloaded for free for all computers and related devices. You should also try to solve other problems that affect your sleep.

To help reduce eye strain, which is a common concern for people who frequently use screens, the American Academy of Ophthalmology recommends using the 20-20-20 rule to take regular breaks. Every 20 minutes, move your gaze away from the screen about 20 feet away for about 20 seconds.

You should also get as much sunlight as possible between screen uses to provide strong circadian rhythms and alarm stimuli, especially when you are indoors most of the time.

As for my brother, he doesn't watch TV much and prefers to read printed books at night. He agrees that he may be experiencing the placebo effect of the blue light filter on the new glasses-or just because his prescription is correct, so he sleeps better and therefore his eyestrain is lessened.

As a service to our readers, Harvard Health Press provides access to our archived content library. Please note the last review or update date for all articles. Nothing on this website, regardless of the date, should be used as a substitute for direct medical advice from your doctor or other qualified clinicians.

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