In our last article we looked at ultraviolet radiation (UVR) and how we can use glasses to protect our eyes, and the delicate skin surrounding them, by minimising UV exposure and therefore reducing the risk for ocular disease and skin cancers. There’s also now a growing body of evidence that suggests we really need to be protecting our eyes not only from UVR but also Blue-Violet Light (BVL).
Fig 1. In the visible spectrum blue light has the shortest wavelengths and highest energy, whilst red light has the longest wavelengths and lowest energy.
Whilst UVC gets blocked by our atmosphere, UVA and UVB can penetrate the structures in our eye, with a small amount of UVA reaching our retina. Almost all visible light, including blue light, reaches our retina.
WHAT IS BLUE LIGHT?
Visible light is made up of a range of colours, which means a range of wavelengths and energies. Blue light sits at the lower end of the visible spectrum, next to UVR, and is the most energetic wavelength of visible light that reaches the retina. This is important because whilst our cornea and lens absorbs some UVR, virtually 100% of that high-energy visible blue light passes through these structures and reaches our retina at the back of the eye.
The higher energy blue light also scatters more than other wavelengths, reducing contrast, and contributing to symptoms of digital fatigue, such as eyestrain, discomfort, and difficulty focusing, when on devices.
NOT ALL BLUE IS BAD
As you can see from the above image, the visible spectrum runs from 380-700nm, and blue light covers about a third of that, from 380-500nm. But not all this blue light is harmful. We can classify blue light into the following categories:
· Violet light (380-415nm)
· Blue-Violet light (415-455nm) ¬ harmful blue-violet
· Blue light (455-500nm) ¬ essential blue
‘Bad’ blue-violet light has those shorter wavelengths and higher energies, and has been shown to be the most harmful range for our retina.
‘Good’ essential blue light has a lower energy, and is necessary for mood, alertness, memory and cognitive function, and to regulate our circadian rhythm (our sleep/wake cycle).
It’s crucial then that our glasses don’t block 100% of blue light, rather they specifically target and block these harmful wavelengths, whilst still allowing transmission of essential blue wavelengths.
BLUE LIGHT IS EVERYWHERE
It’s common knowledge that our devices are a big source of BVL. Anecdotally we’re spending more and more time in front of the screen, and whether it’s in the workplace or at home, we’re often exposed to multiple devices, and sources, at once.
LED’s are becoming the more popular choice for lighting due to their high energy efficiency, but what you may not realise is that these give off a lot of blue light. The image to the right shows a blue peak for LEDs that doesn’t really exist for other artificial light sources. This may be minimised by fitting a ‘warm white’ LED bulb but often workplaces will have a bright ‘cool white’ colour, as well as multiple screens.
But, we aren’t just exposed to blue light indoors – we can’t forget that the largest emitter of blue light is our sun. Blue-tinted daylight is what tells us it’s day-time and to stay awake, so you can see how excessive blue-light exposure might interfere with our sleep.
SO, WHAT CAN I DO ABOUT IT?
· Practice good screen hygiene to reduce symptoms of computer vision syndrome
o Lower screen brightness
o Use ‘Night Mode’ or add a screen filter to reduce blue output
o Increase your working distances when using devices
o Reduce time on devices, especially near bedtime
· Switch ‘cool white’ LED bulbs to ‘warm white’ to reduce blue output
· Invest in high-quality blue-filtering prescription glasses
Blue-blocking glasses
With studies showing an increase in daily screen time linked to higher reports of ‘tired eyes’ and digital eyestrain, interest in blue-blocking glasses are on the rise, and we’re seeing a flood of products introduced to the market with varying degrees of quality. When looking at blue-blocking glasses it’s important to make sure that they aren’t blocking all of the blue spectrum – to be effective they need to selectively block those harmful wavelengths whilst still allowing the good blue light through.
At Eyes of Howick our targeted blue-blocking options include:
Crizal Prevencia
This blue-blocking anti-reflective coating is applied to clear lenses and blocks 20% of harmful BVL, whilst allowing essential blue light through.
Smart Blue Filter
Essilor’s blue-blocking technology is embedded into the polymer of the lens and absorbs at least 20% of harmful BVL, whilst allowing transmission of essential blue. Smart Blue Filter can be used in conjunction with the Prevencia coating to increase protection, and block at least 30% of harmful BVL.
Transitions
Photochromic lenses block at least 20% of harmful BVL indoors, and over 85% outdoors as they transition into a darker tint. Transitions can be used in conjunction with the Prevencia coating to further increase indoor protection to BVL.
Transitions lenses also provide 100% UV-blocking capability and a high E-SPF 25+.
Xperio Polarised lenses
Polarised sunglasses for outdoor use provide protection by blocking up to 92% of harmful BVL, as well as offering high UV protection with an E-SPF 50+.
Are blue-blockers right for me?
The main concerns currently with blue light is its link to digital eyestrain and potential increased risk for eye disease.
If you consider the number of sources of blue light you’re exposed to daily (including the sun), and especially the length of time spent staring at a screen, or under LED lights, the exposure starts to add up pretty quickly. And whilst there’s no evidence to date that prophylactically wearing a blue-light filter will prevent or delay the onset of retinal disease (i.e. macula degeneration), research does show that those high-energy wavelengths are harmful to retinal cells. Certainly, our extended use of devices is relatively new and so more long-term data is needed to determine whether this cumulative exposure has a permanent effect, but in the meantime we recommend taking a proactive approach to the health of your eyes and consider using blue-light blocking glasses to supplement some of the behavioural changes suggested above.
If you do spend a prolonged period in front of the screen and are experiencing symptoms of digital fatigue or discomfort, blue light could definitely be a contributing factor, but we also need to consider your refractive error, or prescription. Certain types of prescriptions are more likely to cause symptoms of headache, eyestrain, fatigue, blur etc., and need to be addressed in conjunction with a blue light filter.
This is why at Eyes of Howick Optometrists, we always recommend having an up-to-date examination and prescription before purchasing new eyewear, so that your new glasses will be best suited to your needs and will be most effective at treating your symptoms.
If you’re interested in ways to protect your eyes from blue light, get in touch with us today for a quote, or visit us in-store to have a look at our range of options on offer.