By Eyecare NG

Introduction   |  Sources   |   Effect on Health   |   Harmful Effect on Eye Health   |   How to Minimize Exposure


You may have heard of blue light and wondered what it is. To understand blue light, we will explain light briefly.

Light is a form of energy. It is made up of electromagnetic particles and travels from one point to another as waves. As light travels, it emits energy. The longer the wavelength of the light, the smaller the energy it emits and vice versa.

There are two parts of light – Visible light and non-visible light. The visible light is the part of light that we see with our eyes as white light. Its components include: red, orange, yellow, green, blue, indigo and violet. The non-visible part of the light cannot be seen with the eyes. Its components include:  gamma rays, x-rays, ultraviolet rays, infra-red rays and radio waves.

Blue light is part of the visible light with wavelength ranging from 380nm to 500nm. Its wavelength is short and so it emits high energy.

Blue light is available everywhere and is beneficial to human health. However, it can also be detrimental to health if there is excessive exposure to it.

Sources of blue light

Some sources of blue light include;

  • The Sun: This is the biggest source of blue light. As light passes through the atmosphere, the blue rays (high energy rays) are scattered by suspended water molecules and air molecules and this makes cloudless sky look blue.
  • Fluorescent lights, other light bulbs including energy saving bulbs.
  • LED lights such as those normally used in flat screen television.
  • Computer display screens
  • Electronic and digital devices like tablets, smart phones, e-readers etc

Effect of blue light on health

Exposure to blue light helps during the day helps maintain the circadian rhythm (that is, the body’s natural clock regulating wakefulness and sleep cycle. However, when one is exposed to too much blue light in the night especially close to bedtime, it disrupts the circadian rhythm resulting in sleepless nights. This is because blue light lowers the production of melatonin, the hormone that regulates sleep.  In other words, excessive exposure to blue light can cause insomnia and sleep disorders.

Blue light boosts alertness, increases reaction time, elevates one’s mood and increases the feeling of well-being. It has also been shown to improve memory and cognitive ability.

On the other hand, some studies have also associated blue light with an increased risk of depression, diabetes, obesity, heart disease and some eye diseases as well as a higher occurrence of some certain cancers (like breast and prostate cancers).

Harmful effect of blue light on eye health

Digital strain/ computer vision syndrome

Blue light is easily scattered and often difficult to bring to focus.  The scattered light reduces contrast on screens and this contributes to digital eye strain.

Development of age related macular degeneration

Blue light exposure can lead to the development of age related macular degeneration and other retinal damages. This is because the eye does not block the high energy blue light. Hence, blue light entering the eye gets to the retina where it can cause damages that result in vision loss.  This is more likely to occur in people who spend long hours on digital devices or those who have undergone cataract surgery.

How to minimize blue light exposure

Use blue light filters

Blue light emitted from the screen of digital devices such as smartphones, computers and tablets can be significantly reduced using blue light filters. Some of these filters can be installed as an application in the digital devices or contained in screen guards that can be placed over the screen of these devices. Some applications also have night mode settings which when activated can reduce the amount of blue light that gets into the eye.

Wear digital eyeglasses

These are modern eyeglasses that have been designed for better performance, clarity and comfort while using digital devices. These eyeglasses reduce glare, improves contrast on the screens and blocks significant amount of blue light.

Make lifestyle changes

Some lifestyle changes can minimize exposure to blue light and its impact. This includes reading a print book instead of an electronic version, making deliberate effort to go screen free at least two hours before bed time as well making  use of dim red lights as night lights (as red light does not have significant impact on the circadian rhythm).