Why block blue light


Many people watch Netflix (or similar services) in the evening to relax and wind down. Unfortunately watching late night TV does not help us sleep better. In a recent post about the miracles of sleep (here) and the techniques on how to improve sleep I wrote that we need to avoid blue light and there were a few questions so as to why is this. Blue light has very important functions but it is also very disruptive so let me try to clarify some of the questions and hopefully you understand how important it is to block blue lights. Knowledge is power!

The basics

Blue light is a one of the colours on the visible light spectrum that makes up about one third of all visible light and is found in 450 to 495 nanometer range.


The blue light colour range is found emitted in both natural sunlight and also in man-made artificial light sources. 

Blue light from the sun

The light that comes from the sun contains a wide spectrum of colours of light. When combined this range of colours form what we call white light, also known as sunlight. Blue light that comes from sunlight is a beneficial for our natural circadian rhythms.

Although excessive sun exposure can be harmful, the blue light in sunlight is balanced with red light and invisible infrared (IR) light, which has been shown to heal and repair cellular damage.

Artificial blue light

On the other hand, blue light that comes from artificial sources is a disruptor of circadian rhythms thus leading to health issues.

This is because the light that comes from light bulbs doesn’t contain the same desired distribution of colours in the short and long wavelengths like sunlight does. LED light typically produces more light in the blue light spectrum and is not balanced out with other colour wavelengths as found in sunlight. Blue light is able to pass through the cornea and lens and reach the retina. This is why excessive blue light exposure from  lightbulbs can be damaging to the eyes.

Examples of sources of artificial blue light include LED, incandescent and fluorescent light bulbs. So, artificial blue light is emitted by indoor and outdoor light bulbs and digital screens from computers, laptops, tablet computers, cellphones and gaming devices.This is in contrast to blue light that comes from artificial light sources that is not balanced out by red light and infra-red light wavelengths.

Fake light everywhere!


  • Vitamin-D is a critical co-factor in many processes in our body

Light is energy!

Each type of colour of light contains different amounts of energy. The warmer colours such as red, orange and yellows are low energy and the cooler colours like purple, blue and green all contain high amounts of energy. The highest energy visible light is often called blue-violet light or blue light.

This is why we want to wake up and get plenty of sun. It resets our circadian rythm by giving us the right amount of energy from the blue light spectrum.

On the other hand too much unbalanced blue light at the wrong time of the day has many negative effects as you will see below.

Impacts and what to do

Too much blue-light either during the day and especially in the evening is very disturbing and it can lead to some serious issues such as

  • Strain on the eyes
  • Disturbed sleep 
  • Possible damage to the retina cells at the back of the eye
  • Headaches
  • Possible contribution to forming cataracts

Today I would like to focus on the first two points as I believe most people have sleep issues and tired eyes because of too much blue light.

Digital eye strain

Digital eye strain is also referred to as computer vision syndrome and is a set of vision related problems that result from extensive use of a computer, smart phone, or tablet. The majority of people that use a computer will at some point experience digital eye strain.

Digital eyestrain has symptoms such as dry eyes, watery eyes, headaches, stiff neck or fatigue. The symptoms of digital eyestrain typically occur after using a computer for long periods of time. What causes digital eyestrain is high energy visible light (HEV) which is another name of blue light and is emitted in large quantities from your computer or laptop screens. This blue light can cause stress to the cells in our eyes, causing us to strain to see. The blue light also flickers which causes our brains to work harder which can result in headaches or migraines.

By wearing computer glasses during the day, when working on a computer, we can reduce the amount of blue light that passes through our eyes which leads to a reduction in the symptoms of digital eyestrain, fatigue and headaches.

  • The best computer glasses are ones that filter down only a small amount of blue light. We do not want to block blue light during the day as we need some blue light to function properly. This is why a good quality pair of computer glasses are great at protecting your eyes from digital eyestrain throughout the day.
  • The worst computer glasses are ones which filter down violet or green light, these are not good for during the daytime as the damaging light found in computer screens is blue light. 
  • During the daytime you do not want to block completely blue light. Blue light is essential during the day. What colour is the sky? Blue! What we want to block is the excess artificial blue-light when we are working in an office under artificial blue light or using our digital devices and computers we are bombarding our eyes!
  • In order to reduce the strain on our eyes we must also reduce flickering blue light by LED lights in our office and home. Aim for light bulbs with zero flicker and no blue light.


  • Computer glasses help relieve symptoms of digital eyestrain. 
  • Get a pair of computer glasses to filter down, but not block, some of the blue-light.

Disturbed Sleep ( due to melatonin secretion)

It is important to understand that melatonin starts to be secreted in a human with optimal circadian rhythms. 

That time starts typically around 6pm, steadily rises to around 1am when it peaks and then starts to decrease until it bottoms out around 7am. When melatonin bottoms out, cortisol peaks. Under the correct light and dark cycles melatonin release can last for about 12 hours. 

However in our modern world we are exposed to artificial light which causes a shortening of the dark circadian period. What this means is less melatonin and less less quality sleep. Those that we not wearing the blue light blocking glasses experience up-to 63% less melatonin secretion and wake up feeling tired. Has this happened to you?!

To correct this issue we mean to remove the blue and green light from 400-550nm to allow melatonin secrition. This will allow for a correct circadian clock.  Note that green light (between 500-550nm) also suppresses melatonin so we need to remove that.

  • After sunset you must block 100% of blue light and also most green light. The range of light you need to block is 100% between 400-550nm. This means the glasses need to be dark amber, orange or red in colour. 
  • Clear lenses, will not block blue light. There is a big misconception that people can wear clear computer glasses and block all blue light and sleep better. A clear lens cannot block 100% of blue and green light between 400-550nm.

For geeks

  • For optimal sleep you must block 100% of the green light found between 500-550nm. 
  • Green light runs from 500-570nm. The green light found between 551-570nm does not impact melatonin levels to the same extent than lower green light. Therefore, its best to leave that light present and not ruin your vision experience post sunset. 
  • In the presence of yellow, amber and red light as they do not impact melatonin secretion.


  • For a good night sleep buy a pair of blue light blocking glasses that block all light from 400-550nm.
  • Blue-light glasses are either orange or red

Final Thoughts

  • Blue light is essential in the morning to wake us up and give us energy but we need to manage it carefully later in the day.
  • Artificial blue can be very harmful and it is not balanced in the way the light from the sun is.
  • Aim to filter during the day some of the blue light by wearing a pair of computer glasses.
  • In they evening try to block all blue and green light between 400-550nm why wearing a pair of orange or red glasses. This way you can still enjoy your favourite Netflix series and still have a good night sleep.

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