Good vs. Bad Blue Light

By on

Guest post by VSP optometrist Gary Morgan

There is no escaping the fact that most of us are surrounded by digital devices. Whether in the office, at home, or in the palm of your hand, these devices are ubiquitous. They also emit harmful blue light and there has been a lot of media interest about the impact it is having on our health. As part of that conversation, an unsettling term has surfaced: good blue light.  How did this term come about? First, we need to take a step back and discuss blue light in terms of wavelength. Our visual system detects wavelengths of light between approximately 400-750 nanometers (nm). The shorter wavelengths have higher energy and a cooler color (blue light is defined as 400-500nm). We can also further divide these wavelengths of light by their effects on our vision and health.

What is “bad” blue light?

Blue light below 430nm is most responsible for the tired feeling our eyes may get after viewing digital screens; we call this digital eyestrain or visual strain.  Blue light below 460 nm is what has been linked to oxidative retinal damage. The cumulative effect of this light has been linked to the potential development of age-related macular degeneration (AMD), the leading cause of blindness for people over 55.  So light below 460nm has been labeled ‘bad blue light’

BlogPicWhat is “good” blue light?

Blue light above 460nm controls the secretion of our sleep hormone, melatonin.  In what used to be considered a normal day, we would wake up in the morning, receive exposure to sunlight, and our body’s internal clock would tell our pineal gland to stop secreting melatonin.  This would make us feel awake, alert, energetic, and some would say happy.  This is how we want to feel during the day, thus the term ‘good blue light’ has been used to describe these longer blue wavelengths.  In fact, in some climates where sunlight is scarce during winter, people have less blue light exposure and may develop seasonal affective disorder (SAD) in which they feel tired and depressed.  Therapy lights that emit long blue light wavelengths are a common treatment for SAD.

When does “good” blue light go bad?

Digital devices emit the full spectrum of blue light. Exposure to longer wavelength blue light at night affects melatonin secretion and disrupts our sleep.  Should we really classify 460-500nm light as good when it interferes with our ability to fall asleep? Is it a good thing that our children are not getting enough sleep, which for some may lead to ADHD-like symptoms? How happy are we to be awake at 2:00 a.m. because we worked on our computer or tablet until 11:00 p.m., delaying the onset of melatonin secretion?

None of these implications that are currently being extensively researched sound very good. While we need exposure to 460-490nm light during the day, we don’t need it after sunset.  So when you hear the term ‘good blue light’, take care to keep it in the proper context.  Your health could depend on it.

Learn more about how you can reduce blue light exposure with lens coatings like Sharper Image TechShield. 


  • Roger Neal says:

    This article is just a poorly camouflaged sales pitch. It doesn’t provide any solutions other than going to an expensive store to buy a product. This isn’t helpful at all. I just got new glasses and don’t want to add anything onto them.

  • James Middleton says:

    Nice to know. You might want to talk to Microsoft about their screen background color palette. I believe the blue I selected may fall into the sub 460nm range noted in this article. I changed it today.

  • Jenny says:

    Do flat screen and/or regular TVs emit blue light?

  • don says:

    So, what do we do to prevent bad blue light from the computer or in general? The article serious lacks in that respect.

  • Joy says:

    Am using glasses to block the blue light. My eyes don’t get nearly as irritated or tired and I’m on the computer likely 6 hours a day at least.

  • Santosh Poojari says:

    Really wonderful piece of information which I was searching for long time. I am too facing tired eyes since long and was not knowing what to do. Will need to take care of my schedules and timings for working on computer devices.

  • Robert Warren says:

    Is there a way to measure the wave length of blue light? Easy is better.

  • Bob C. says:

    I use a program called f.lux that automatically shifts the display color from blue to a warm red based on time of day. Get it at
    Available for Windows/Mac/Linux and some apple “i” devices.

  • Virgil says:

    And I was hoping it would at mention those, blinding, bright blue headlights on some vehicles.

  • shyaco says:

    I would like to see more information about what blue light each of our devices emits and/or how to find that info. Also would be helpful to know how to counteract blue light

  • Pat Parker says:

    My daughter got some nightlights that are blue. Are these dangerous?

  • Pat Ciavola says:

    Great article and something we all should pay attention to. We need to turn off our digital devices earlier in the evening to get a good night’s sleep.

  • Brookie Bear says:

    i like it

  • Brookie Bear says:

    Ot’s really nice

  • […] There’s blue light that comes from the screen, and it’s been linked to an increase in eye fatigue at the end of the day. Exposure to this high-energy light has been linked to digital eye strain in as little as two hours of exposure. Symptoms of digital eye strain include things like tired, dry, burning, or watery eyes. The problem with TV and computer use comes when you’re using either for long periods of time. According to recent surveys, most of us spend about nine hours a day on our digital devices. […]

  • Leave a Reply

    Your email address will not be published.

    You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>