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BLUE LIGHT

What is Blue Light?

Understanding blue light and its effects:

The spectrum of light covers various wavelengths and energies of light some of which form the visible spectrum from Red through to Blue and violet, as well as the non-visible spectrum which includes things such as Infra-red, Ultraviolet, X Rays and Gamma Rays.

The Earth’s atmosphere luckily blocks a lot of these short wavelength high energy rays some of which would threaten our very existence should they reach the earths’ surface unfiltered, whilst others such as UV Rays are still able to penetrate the atmosphere and although we cannot see them, we are well aware of the damage they can cause.

Both our skin and our eyes absorb light, on the skin UV light causes sunburn and skin damage that can eventually lead to some types of cancers and in our eyes these effects are no different. Right next door to UV light in the spectrum lies high frequency, high energy blue light and recent studies on the effects of blue light have demonstrated that some of the effects of UV light on our eyes can also be seen from prolonged exposure to this high energy blue light as well. It is important to note that this does not include all blue light, the most damaging blue light lies in the wavelengths from 415 to 455nm which is the blue-violet spectrum.

Where does blue light come from?

Blue light forms part of the visible spectrum of light and comes form the sun as well as many light emitting sources. In years gone by most internal lighting was made using mostly incandescent light bulbs which had a much larger content of yellow emissions. However, with a shift to the more modern white lights, most homes and internal lighting is now achieved using L.E.D lighting which gives off a much higher concentration of blue light emissions. Not only are we using this for our lighting needs, but most of our electronic devices are now using this same technology to power up our screens increasing our exposure to blue light often viewed at much closer distances.

Why worry about Blue Light?

Blue light, in moderation can be good for us. It exists naturally outdoors from the sun, regulating our circadian rhythm, controlling our sleep and awake times and promotes a sense of wellbeing.

There are also many indoor sources of blue light, including fluorescent and LED lighting and flat-screen televisions. Our smart phones, electronic notebooks, computers and other digital devices emit significant amounts of blue light and the amount of time we spend using these devices together with the proximity of these screens to our face has many health care professionals concerned about possible long-term effects of blue light on eye health.

Our eyes are not very good at blocking blue light with virtually all visible blue light passing through to the retina damaging the light sensitive cells and increasing the risk of macular degeneration – the leading cause of blindness in modern society.

What is digital eye strain?

We spend hours each day staring at our computers, smart phones, tvs and other digital devices and this can lead to eye strain. Blue light is a high frequency, high energy, short wave length light which both bends and reflects easily. This causes glare which confuses the eye and makes it difficult for us to focus easily, straining the eyes. Dry and itchy eyes, loss of focus, blurry vision, day time fatigue and headaches and neck pain are all symptoms of too much Blue light and digital eye strain.

Blue light can also lead to other forms of fatigue beyond eyestrain. At night, artificial blue light disrupts the circadian rhythm that causes the natural release of melatonin that helps us sleep. Falling asleep can be more difficult and we are left fatigued the next day. Circadian disruption can also lead to other more serious side effects, including depression and weight gain!

What are the effects of blue light?

Blue light itself, is not all bad, like everything in life however our exposure to it, is best kept to moderation. Extended exposure to relatively high levels of blue light have been demonstrated to have the following effects

1/ Accelerated cell death: Several research articles have shown that prolonged exposure to high energy blue light has been shown to lead to an increase in free radicals leading to cell impairment and accelerated cell death, in the eyes particularly this has been observed in:

  • The cornea – leading to inflammation and dry eyes
  • The crystalline lens – leading to lens discolouration and contributing to cataract formation
  • The retina – leading to photoreceptor cell death which is a contributing factor in macula degeneration

2/ Change in sleep patterns: As mentioned there is a significant amount of blue light emissions from natural sunlight. Blue light exposure has been shown to reduce the production of a hormone in the brain called melatonin which assists in our normal sleep and wake patterns known as our circadian rhythm. As sunlight intensity and hence blue light intensity peaks around the middle of the day this is normally the time at which our melatonin levels are lowest, allowing us to maintain an awake state. As the sun starts to set in the latter part of the day and there is less blue light stimulation so there is a gradual rise in our melatonin levels in the brain preparing us for a night of sleep. The intervention of false lighting and in particular modern lighting and digital screens which are rich in blue light, interferes with our level of melatonin production from over stimulation of blue light affecting the brains normal circadian rhythms and disturbing our patterns of rest, wakefulness and mood. The results of studies investigating how long before bedtime you should avoid bright light and specifically blue light varies between two to three hours. For many people in today’s busy modern world this is unfortunately not always going to be a practical option. In a research programme at Toronto University the effects on melatonin of bright indoor light whilst wearing blue light filtering goggles was shown to be no more severe than only being exposed to dim light and hence a greatly reduced impact on our natural melatonin production.

3/ Glare – Glare is scattered light caused by reflections from smooth surfaces such as water, buildings and glass. Light can be both bent and reflected and the shorter the wavelength of light the more it bends and the more it reflects causing glare as well. Blue light is the shortest wavelength amongst the visible spectrum of light that we can see, and therefore is the largest contributor to reflective glare within the visible spectrum.

Viewing normal print on paper is much easier for the eyes to focus on than reading digital screens as it offers an exact physical surface and therefore provides a good focal plane for the eyes to rest their focus on. Print on digital devices however is seen by viewing thousands of little light sources (diodes) shining back at you, each creating its own glare pattern and making it difficult for the eyes to establish an exact focal plane on which to focus. Not only does this glare interfere with what you are trying to view around it, but it also creates a constant tiring and headache forming scanning action in the muscles of the eyes as they try to establish where the best focal plane and focus is achieved.

How do blue light glasses help?

Important to keep perspective...

Whilst there are many studies demonstrating the adverse effects of blue light on our eyes and vision, there are also other studies that show that we are not 100% certain that the amount of blue light emitted from our digital devices is sufficient to create all of the problems associated with high intensity blue light exposure.

So, should we or shouldn’t we make use of blue light glasses?

If we begin our conversation around vision comfort, and understand the glare factors and the effect on vision that blue light creates, it stands to reason, that if we can reduce this glare and enhance contrast, it will be easier for the eyes to focus on our screens, providing more clarity and comfortable vision, so reducing eyestrain during the time we are viewing our digital devices. This alone provides a strong argument in the benefit of wearing blue light glasses.

Taking this one step further, the amount of blue light emissions we are each subjected to will vary, one person to another. Factors such as the number of screens, the brightness of your screens, the type of ambient lighting, the amount of light reflecting from your screens, the number of hours that you use screens and the proximity that your screens are from you, are all so variant that it becomes difficult to quantify the amount of blue light we are each being subjected to on a daily basis and how severe its effects may be.

If the amount of blue light you are exposed is high enough to create the damaging physiological effects mentioned above then filtering out these unwanted wavelengths should go a long way to preserving the health of your eyes, along with the added advantage of improved vision comfort. On the other hand if the amount of blue light you are exposed to is too low to cause any of these effects of damage then at the very least you have peace of mind that you are protecting your eyes along with improved vision comfort whilst viewing your devices.

Will blue light glasses stop my symptoms of headaches and eyestrain when I view my digital screens?

Blue light is a contributing factor in computer vision syndrome but by no means the only cause. If you are suffering the effects of digital eyestrain, headaches, blur or dry eyes, when viewing your digital devices, you should consult your eyecare practitioner first. Once you have ruled out any other factors that could be causing your symptoms then blue light effects could be a possible cause. Rarely is there a single reason for such symptoms, so it is important that you obtain professional advice when trying to counter the effects that you are suffering. It is for this reason that Blue light glasses are available in both non-prescription and prescription options in case your solution requires a more tailored approach.

How do blue light glasses work?

Blue light glasses reduce the amount of light that passes through the lenses and on to your eyes. They do this by one of two methods:

1/ In-mass blue light glasses: These lenses do not have an obvious blue hue to them. Here chromophores are rather added to the actual spectacle lens substrate, these act in an absorbtive capacity to absorb blue light in the shorter wavelengths usually up to 420nm to prevent it from going any further than the lens itself, thus protecting your eyes from its effects.

2/ Blue light lens coatings: Through the use of metal oxides coated onto the lens surface, modern science can affect the way light either passes through or reflects from a lens surface through a process called constructive and destructive interference. Each layer of coating can be varied to either let a certain wavelength of light through the lens or to cause it to reflect away from the lens. In blue light lenses a specific combination of metal oxide layers are used to reflect the unwanted short wavelength, high frequency blue light away from the lens so it cannot pass through and on to your eyes. Blue coated lenses will usually have a slight blue tinge to them.

Will blue light glasses make everything look yellow?

The original forms of blue light glasses used to create a fair amount of yellowing to the wearers view. As we have found out more about blue light and its effects, so too have we been able to narrow down the arena of wavelengths that we need to filter. As a result of this, new generation blue light glasses are less yellowing than their original forerunners, however all blue light forms part of the visible spectrum so some degree of colour shift will always occur if you block parts of the visible spectrum. Your ability to discern colour and differentiate varying hues will however seldom be affected using todays’ technology.

 

References

  • https://bmjophth.bmj.com/content/3/1/e000146
  • https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288536/
  • https://www.essilorusa.com/newsroom/visible-and-invisible-light