The ubiquitous use of smartphones, tablets, laptops and PCs at work and at home is exposing us to more and more blue light. But what exactly is blue light? Does it really harm our eyes? And what can we do to prevent its pernicious effects?
As a diabetic you know that several parts of the eye are highly susceptible to damage and that you have a high risk of developing three different diseases of the eye: glaucoma, cataracts and retinopathy.
You also know that to protect your eyes you must keep your blood glucose, blood pressure and cholesterol levels under control.
Diabetics use desktop computers, laptops, tablets and smartphones just as frequently as non-diabetics. Now it seems that, in order to protect our eyes, we also need to avoid excessive exposure to blue light which has been shown to cause irreversible loss of eye function and increase the risk to of developing age-related macular degeneration.
What is light?
Light consists of electromagnetic particles that travel in waves. These waves emit energy and their length varies. The strength of the energy these waves emit varies according to their length … the shorter the wavelength, the higher the energy.
The electromagnetic spectrum is made up of all these light-waves, in a continuum running from very short (high energy) waves to very long (low energy) light-waves.
The light-waves in the continuum are grouped into several types. From the shortest waves to the longest, these are … gamma rays … x-rays … ultraviolet (UV) rays … visible light … infrared light … radio waves.
We humans can only see some of these light-waves, ie the part in the middle called the visible light. This section of the electromagnetic spectrum gives us the range of colours that we can see.
These are … again running from the shortest to the longest waves … violet … indigo … blue … green … yellow … orange … red.
White light, infrared rays and ultra-violet (UV) light
White light, ie sunlight, is a combination of all the different types of waves in the visible light part of the spectrum.
The waves in the ‘red’ end of the visible spectrum are the longest in length and have the lowest energy compared to waves at the ‘blue’ end.
The electromagnetic rays just beyond the red end of the visible light spectrum are called infrared rays. They are invisible.
The blue light-waves with the shortest wavelengths are sometimes called blue-violet or violet. Hence the electromagnetic rays just beyond the visible light spectrum are called ultra-violet (UV) rays.
What is blue light?
Blue light is the portion of the visible light spectrum with the shortest wavelengths and the highest energy. It comprises about one-third of all visible light.
Blue light is also called high-energy visible (HEV) light. It is HEV light that makes a cloudless sky look blue.
There are many sources of blue light. Sunlight is the main source, and being outdoors during the day time is how most of us get most of our exposure to it.
There are also many man-made, indoor sources of blue light. These include fluorescent and LED lighting, flat-screen TVs, and the display screens of computer, electronic notebooks, smartphones and other digital devices. The amount of HEV light these devices emit is only a fraction of the amount we get from the sun.
The time people spend using electronic devices, which are usually positioned close to their faces, averages in excess of five hours a day in the Western world. But this is just the average. For many people, exposure to blue light from electronic devices can be double that average or even more. This has health professionals concerned about the long-term adverse effects on our eyes.
How much blue light do we absorb?
Light is transmitted to the retina through the lens. The amount of light transmitted by the lens is age-dependent. In young children, more than 65% of blue light gets through. This rate goes down over time. By the age of 25, only 20% of blue light is transmitted to the retina.
The decreased transmission of blue light occurs as the lenses of our eyes naturally yellow. Over time the yellowing lenses absorb more and more blue light, thus preventing it from reaching the retina.
As a result of this natural process, younger people are more susceptible to the effects of blue light than adults. In addition, they use devices that emit blue light, such as tablets, more frequently than adults. And they are more likely to be exposed to more blue light sources over their entire lifetimes.
Although older adults absorb less blue light, it is possible that damage to their eyes from prolonged exposure may occur. The relative newness of blue light technology and its ubiquitous use in society means the effects of exposure to blue light from electronic devices are not really known.
Research into the effects of exposure to blue light at varying intensities and frequencies is needed so that the facts of the matter become clear and are based on well-researched persuasive evidence.
Blue light has many benefits. It also has plenty of drawbacks.
Benefits of blue light
Exposure to blue light is actually essential for good health. Its beneficial effects include the following:
- It helps regulate your circadian rhythm
- It boosts alertness
- It helps memory and cognitive function
- It elevates moods
- It can be used in therapeutic medicine
Circadian rhythm … refers to your body’s natural sleep and wake cycles. Exposure to blue light during daytime hours helps you maintain a healthy circadian rhythm so you can sleep well at night.
However, too much blue light at night from (say) reading a tablet or e-reader at bedtime can disrupt this cycle and cause a sleepless night.
Moderate exposure to blue light during the daytime also helps our mental processes and how we feel about things.
Blue light can be used as a medical tool. For example, seasonal affective disorder (SAD) is a type of depression that’s related to the onset of the short dark days of winter. It is often treated successfully with light therapy that contains a significant amount of HEV blue light rays.
Dangers of blue light
Medical professionals and researchers are becoming increasingly concerned about the adverse effects of excessive exposure to blue light. These include:
- Disruptions to circadian rhythm
- Onset of digital eyestrain syndrome
- Permanent eye damage
- Increased risk of certain cancers
- Increased risk of diabetes, heart disease and obesity
- Increased risk of depression
Disruptions to the circadian rhythm … researchers have found that excessive exposure to blue light at night suppresses the production of melatonin.
Melatonin is the hormone that regulars sleep. It is secreted by the pineal gland in inverse proportion to the amount of light received by the retina. Thus chronic exposure to blue light at night reduces the secretion of melatonin and we fail to fall asleep.
Digital eye strain … is a serious medical condition that can affect learning and productivity at work.
Its symptoms include blurry vision, difficulty focusing, dry and irritated eyes, headaches, neck and back pain.
Also known as computer vision syndrome, digital eye strain has overtaken carpal-tunnel syndrome to become the number one complaint relating to the use of computers. One of its main causes is glare.
HEV wavelengths flicker more easily than shorter, weaker wavelengths. This flickering creates a glare that reduces visual contrast so the images on the screen become less sharp and clear and induce us to strain our eye to see properly.
Almost 70% of adults who regularly use digital devices experience some symptoms of digital eye strain yet lack the knowledge to do anything about it.
Digital eye strain can affect children under 10 years of age more severely as their lens and cornea are still transparent and undeveloped, so they are more easily overexposed to blue light.
Permanent eye damage … due to blue light is a real possibility.
For example, research has shown that irreversible functional loss occurs in the retinas of rats when they are exposed to LED lighting at domestic lighting levels. The severity of the damage is four times higher at night than during the day.
It seems reasonable to presume that chronic exposure to blue light would damage the retinas of humans in a similar manner.
Other studies on animals have shown that age-related macular degeneration (AMD) can be induced by exposure to blue light. As every diabetic is (or should be) aware, macular degeneration can lead to loss of vision and eventually blindness.
The retina is a thin layer of light-sensitive tissue that lines the inner eyeball. The macula is the functional centre of the retina. It gives us the ability to see “20/20” and provides the best colour vision.
Melanin is a broad term for a group of natural pigments found in most organisms. One of these is the macular pigment which gives the macula its yellow colour. These natural pigments in our skin, hair and eyes absorb UV and blue light rays.
The retina can be harmed by high-energy blue-violet light that penetrates the macular pigment.
The macular pigment plays a critical role in protecting the macula from blue light and helping to maintain the function of the macula.
Unfortunately we lose melanin as we grow older and by the age of 65 half its protection is gone, making us more susceptible to eye diseases such as AMD.
Increased risks … of breast and prostate cancers, diabetes, heart disease, obesity and depression have been linked by researchers at Harvard to exposure to blue light while working night shifts. These studies, however, still need to be confirmed by additional research.
How to protect yourself from blue-light
Besides giving up your use of computers and smartphones―probably impossible for most of us by now―there are several things you can do to protect yourself from blue light and various forms of digital eye strain:
- Turn on the night light settings on your computer
- Use a blue light filter over your computer screen
- Wear blue-blocking glasses
- Use single vision filtered prescription glasses
- Wear glasses with glare-reducing anti-reflective coatings
- Try photo-chromic lenses
Night-light settings … on a computer using Windows operating system, you can turn off the blue light on your computer screen.
But first you have to activate night-light settings. Here’s how to do so in Windows 10:
- Open the start menu
- Scroll down to ‘Settings’
- Click ‘Settings’ … the Settings menu will open up
- Click on ‘System’
- Click ‘Display’
- Toggle the night-light switch to ‘On’
- Click ‘Night light settings’
Now you have several choices. You can choose to (1) turn on the night-light so that it remains on permanently (click Turn on now), (2) schedule it so that it comes on and goes off at a particular time (say 9pm to 6am), or (3) schedule it so that it comes at dusk and turns off at dawn.
Option (3) requires your location to be turned on. You choose it by clicking on ‘Location settings’ and toggling ‘Location service’ to ‘on’.
Blue light filters … are screens that cover the display monitors of PCs, tablets and smartphones. They prevent significant amounts of blue light from reaching your eyes but do not affect the visibility of the display. Some are made of thin tempered glass that also protects the screen from scratches.
Blue-blocking glasses … are clear eyeglass lenses with a blue light filter. They can help reduce your exposure to blue light from PCs and other digital devices.
If you don’t require prescription lenses or you wear contact lenses, you can get blue-blocking glasses made of plain glass that filters out blue light. They are also available with prescription lenses.
Single-vision filtered prescription glasses … are prescription glasses that optimise your vision for a point at a fixed distance, ie from your eyes to the screen of your PC.
As well as containing blue-filters, these lenses have a larger field of view so you can see your entire computer screen clearly. I find them great for reducing eye strain and blurred vision, and an unhealthy slump in my posture.
Anti-reflective coatings … are available on lenses from some manufacturers. These special glare-reducing coatings also block blue light from both the screens of digital devices and natural sunlight.
Photo-chromic lenses … provide protection from UV and blue light both indoors and outdoors. They also darken automatically outdoors in response to UV rays to reduce glare.
My best advice is that you should seek advice from an optician or ophthalmologist you trust. You must also keep blood glucose, blood pressure and cholesterol levels under control.