If you’re someone who works with a laptop or computer most of the day, digital eye strain might be a common experience for you. One of the solutions your optometrist will recommend for comfortable vision is blue light control coating on your spectacles. But did you know that not all blue light control coatings are the same?
Firstly, what is “blue light”?
Sunlight contains rays of different colours, and each ray has different wavelengths and emits different levels or energy. Light waves having longer wavelengths emit less energy, while shorter wavelengths emit higher energy.
Blue light has the shortest wavelength in the visible spectrum, so it’s considered to have the highest energy—and the most harmful.
Is blue light hazardous?
Yes. The wavelength of harmful blue light falls in the range of 400-480 nm. The oxidative damage caused to the retina by blue radiation peaks at 440 nm. It decreases to 80% of the peak at 460 nm and 415 nm. For the sake of comparison, green light, at 500 nm only causes 1/10th of the oxidative damage caused by blue light at 440 nm. Hence, while considering protection from visual display units that emit blue light, it is very important for us to dispense lenses that cut the wavelengths between 420 nm to 460 nm.
According to the National Center for Biotechnology Information (NCBI), “Because of blue light’s short wavelength, the focus is not located in the centre of the retina but rather in the front of the retina, so that the long exposure time to blue light causes a worsening of visual fatigue and nearsightedness.”
What are the sources of blue light?
Blue light is everywhere.
Sunlight is the main source of blue light, and being outdoors during daylight is where most of us get most of our exposure to it. But there are also many man-made, indoor sources of blue light, including fluorescent and LED lighting and flat-screen televisions.
Most notably, the display screens of computers, electronic notebooks, smartphones and other digital devices emit significant amounts of blue light.
What are the risks of blue light exposure?
Increased risk of macular degeneration. High-energy blue light can penetrate into deeper layers of the eye, damaging retinal cells and leading to permanent loss of vision.
- Digital eye strain with prolonged use of devices. Symptoms of digital eye strain, or computer vision syndrome, include blurry vision, difficulty focusing, dry and irritated eyes, headaches, neck and back pain. Children are at risk for eye strain due to their growing use of digital devices.
Different Brands of Blue Light Blocking Coats and their Wavelength Blocking Range
Our catalogue has various brands of ophthalmic lenses that provide protection from the harmful blue wavelength to the wearers. The wavelength blocking range of these lenses vary from one brand to the other. So, it is important for us to know the wavelengths that are blocked by specific brands of lenses:
- HOYA BlueControl:This product is manufactured by HOYA, blocks wavelengths in the range of 420 nm to 460 nm. This lens effectively blocks the most harmful spectrum of blue light. This lens perfectly blocks the harmful range and has no effect on the Cyan-blue light range (good blue light)
- SeeCoat Blue: This product, manufactured by Nikon, blocks wavelengths in the range of 380 nm to 500 nm (starting at 10% blocking of 380 nm, reaching 40% blocking at 410 nm and 90% blocking from 420 nm to 500 nm). In comparison to one of the major brands, this lens gives protection over a wider range in the visible spectrum. However, it could be perceived as a disadvantage by some wearers as this lens blocks more of violet and complete blue wavelengths of the visible spectrum (violet: 380 nm to 450 nm; blue: 450 nm to 495 nm). As a result of this blocking, the wearers usually tend to see everything more yellowish through these lenses than one of the major brands.
- Express Eyecare lenses: The blocking range of these lenses is 395 nm to 415 nm. This is a much narrower range of protection compared to the two lenses discussed above. We can clearly see that the peak of the harmful blue light is allowed to transmit through this lens. Hence, although this lens offers protection from shorter blue wavelengths, in the best interest of our clients, it is better for us to stick to lenses that offer better blue light protection than this lens.
Interesting observation: Recently there had been a confusion regarding the demonstration kit that was given to us by this company to show that a blue light does not pass through their lenses. We have tried to put other blue lenses like Seecoat blue lenses in this demonstration and we were surprised to see that the blue demo light just passed through all the lenses except Express Eyecare lenses. Upon experimenting, we could deduce that the demo light that was given with this kit was in fact an isolated ultraviolet light (similar to the light given with transitions demo). Probably this light has a wavelength at the very end of the UV-A spectrum (around 395 nm). Other lenses do not have an effect on UV wavelength and that was the reason why only this lens was cutting this light and not other lenses.
This finding was reconfirmed when we kept a transitions lens in the path of this demo blue light. The lens changed its colour at the point where the blue light struck the lens. It is a known fact that only UV light can activate transitions lenses. So we can conclude that although this demo kit is good to demonstrate the action of blue lenses to our clients, we have to remember that it is an intelligent tool, designed by this company to show that only their lenses are effective blue wavelength blockers.
- Genop blue lenses: This lens blocks wavelengths up to 400 nm. The harmful blue light of the visible spectrum still gets transmitted through these lenses. And these lenses come with a yellowish tint.
From reviewing the transmission and blocking properties of all the blue lenses that we dispense, we conclude that the first choice of blue lenses on our catalogue (when dispensed to protect the wearer from the harmful blue radiation emitted by visual display units) should be HOYA BlueControl lenses.