Updated: May 27, 2020
Ever since the first smartphone was presented by Apple, our lives and habits have changed, becoming more dependent on these digital electronic devices. On both a personal and workplace environment, television screens, tablets, smartphones and computers are used every day for up to 12 hours. These devices have become the backbone of how we receive and transmit information.
During the COVID-19 pandemic, many adults are asked to work from home, if possible. Children are home schooled by joining e-meeting sessions with their teachers because schools are shutdown. Exposure to multiple digital devices increase. North Americans use digital devices for 2+ hours per day, 60% use them for 5+ hours, and 65% experience symptoms of digital eye strain. Cases of digital eye strain or computer vision syndrome is increasing. More than ever, risks of blue light emitted from electronics are questioned, leading to the development of blue light filter protective coatings.
How is light defined and measured?
Electromagnetic spectrum is used to measure light. The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. This visible spectrum is the wavelengths between 380nm to 740nm.
How do humans perceive colour?
Our perception of colour relies primarily on 4 main light-sensitive cells: three cone photoreceptors and one rod photoreceptors. These visual receptors are found within the retina.
During daytime, the 3 cone photoreceptors actively sense light, and each has a peak sensitivity in either the blue, green or red portions of the visible light spectrum. On the most basic level, our sense of colour is determined by the balance of activity of these 3 cells. When the light is too dim to stimulate the cones, our sense of colour is extinguished. We perceive the world in shades of gray because only one type of photoreceptor, the rod, is maintaining our visual function.
What is blue light?
Blue light is visible light with a wavelength between 400 to 450 nanometers. The light is perceived as blue in colour. However, blue light may be present even when light is perceived as white or another colour.
Shorter wavelengths have higher energy with greater potential to cause damage, while longer wavelengths are relatively harmless. Blue light is of concern because it has more energy per photo of light than other colours in the visible spectrum. On the eye, shorter wavelength blue light is significantly defocused, creating chromatic aberration and significantly affects visual quality and contrast. Sometimes, blue light, at high enough doses, is more likely to cause damage when absorbed by various cells in our body.
Digital Devices and Blue Light
The bright white-light LED backlight screens on electronic devices produce a great amount of blue light. Recent iPhones have a maximum brightness of around 625 candelas per square meter (cd/m2). However, these sources cannot compare to the sun, which yields an ambient illumination more than 10 times greater. Therefore, majority of the blue light actually comes from the sun.
In a 2014 survey conducted by VSP, eyecare providers reported a 50% increase in patient complaints of digital eye strain and effects of blue light exposure. Also stated was a 38% increase in these same complains from children. Without intervention, these statistics will likely increase.
The symptoms of digital eye strain can be broken down into 3 causes: proximity of the digital device to the eye, intensity of light, and frequency and duration of exposure.
Proximity: Users tend to hold digital screens closer to their eyes, increasing demands placed on the eye muscle’s ability to accommodate and converge or diverge. A study published in Optometry and Vision Science shows the mean working distance decreased from 16” with printed text to between 12.68” - 14.25” with digital screen.
Intensity: The intensity of light from digital devices is dependent on the distance the device is held from the eyes. Therefore, the closer you hold the screen, the higher the light intensity eyes receive, leading to eye fatigue.
Frequency and Duration of Exposure: The number of times that you look at digital screens during the day and the length of time spent looking affects symptoms of digital eye strain. The longer and more often you use digital devices, digital eye strain is more prevalent.
In conclusion, the increase in digital screen time usage, and how close the eye is to the screen, leads to intensification of digital eye strain.
How to resolve?
Infused lens materials have pigments or dyes, usually in a slight brown, added to the lens monomer to absorb blue light. They provide reduction along entire blue light range, with their strongest effects at the shortest wavelengths. These lenses appear nearly clear.
Anti-reflection coatings reduce glare and reflect blue light by inducing selectively disruptive light interference. This stimulates a characteristic purple to bluish colour on the surface, and they have a modest effect on the shortest blue light wavelengths.
Multifunctional lens coatings both absorb and reflect blue light through the combination of multi-layer thin film coatings with rare earth compounds and minerals. They have a significant effect on shortest blue light wavelengths associated with visual strain and fatigue.
Photochromic lenses provide variable blue light reduction. Photochromic nanoparticles reform when exposed to UV, absorbing blue light, blocking UV and appearing tinted. When the UV source is removed, the nanoparticles gradually return to their original state and appear colourless, however, they preserve some of their blue light absorptive properties.
Gordon Wood Optical’s dispensing opticians tried out different blue light lens treatments and coatings personally, to conclude they do not squint, nor experience headaches as much as before. We have a couple of brands we exceptionally love. They offer 100% UV protection with infused pigments to relieve digital eye strain. Glare produced by white lights is minimized in dim situations. There is no colour distortion and aberrations when you view out of the resulting product. At the same time practicing the 20-20-20 rule is a great way to make sure that you are not straining your eyes. Every 20 minutes, look at something 20 feet away for 20 seconds.
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