Kids and Blue Light (Part 4 of 4): Keeping Blue Light at Bay

This is part three in a four-part series guest-written by nationally recognized blue light expert, Gary Morgan, OD.

Over the course of the past three blog posts, we have examined why closer working distance, large pupils, and clear crystalline lenses contribute to children being more vulnerable to the adverse effects of blue light. 

So with the “why’s” out of the way, let’s examine the “how’s,” as in, how to help children reduce their blue light exposure and combat digital eye strain.

Reducing Blue Light Exposure: A Two-Pronged Approach

There are two ways to minimize the amount of blue light reaching the retina. We can either decrease the amount of blue light being emitted from the source, or we can filter blue light in front of the eyes.

​Of course a third option would be to limit our children's screen time, but this is becoming more difficult as smartphones and tablets are becoming the primary form in which children learn, socialize, and relax. So let's explore reducing blue light from the sender and to the recipient:

​​1. Decreasing Blue Light at the Source

There are a few ways to decrease blue light emitted from smartphones and tablets. The easiest and most direct way would be to turn down screen brightness. The website Fluxometer.com shows the effect of doing so across the entire visual spectrum for a variety of devices, and equates the light given off by the device as a percentage as bright as daylight.  ​

Screen Protectors
Some screen protectors now include blue light filtration. However, information on their blue light transmittance was unavailable at the time of this article. As will be discussed in a moment, without a transmittance curve, it is impossible to know exactly what these filters are doing.  

Apps
There are apps available to decrease the amount of blue light emitted from phones and tablets. Some of these apps allow you to program your devices to automatically reduce blue light emission at a specified time of day, as well as adjust how much blue light is filtered out. 

2. Reducing Blue Light in Front of the Eyes

The blue-light-reducing lens category has exploded over the past five years. In 2012, there was one company specifically marketing this type of lens. Today, there are nearly 100 different blue-filtering lenses available from manufacturers large and small. These products work by absorbing, reflecting, or both absorbing and reflecting varying wavelengths of blue light. 

Blue Light Reducing Lenses and Coatings
Four types of optical products have been proven to reduce blue light exposure:

1. Infused Lens Materials – Infused lens materials have pigments added to the lens monomer to absorb blue light. These materials reduce blue light across the entire range, but their orange or yellow appearance can be off-putting to patients. Also, depending on intensity, the dyes can have a negative impact on color vision / contrast sensitivity because of blue-blocking properties.   
2. Lens Coatings – These thin-film coatings reflect blue light by inducing selectively disruptive light interference. These coatings have a moderate effect on the shortest blue light range and feature a characteristic purple appearance.
3. Multi-functional Coatings – Multifunctional lens enhancements are multi-layer, thin film coatings with rare earth compounds and minerals that both reflect and absorb blue light. Multifunctional coatings have a significant reductive effect on the shortest blue light wavelengths. These coatings carry the appearance of a typical AR, making them a more aesthetically pleasing option for many patients. TechShield Blue is an example of a multi-functional coating.
4. Photochromic Lenses – Light-reactive lenses also filter blue light. These lenses can offer blue light filtration in clear or dark states, with the tinted states absorbing more blue light than the clear. SunSync Light-Reactive Lenses are an example of photochromic lenses that reduce blue light exposure.

Understanding Blue Light Reduction Percentages

You’ve likely seen (or will see) different companies claiming their products reduce a specific percentage of blue light. However, the question to ask is how much blue light does a particular product filter at different points in the blue light spectrum? The answer is found in looking at a product’s transmittance curve. Below is the transmittance curve for TechShield Blue.

Note that as you move along the x-axis, wavelength increases, and as you move up the y-axis on the left, transmittance increases. So at about 400nm, TechShield Blue reduces blue light transmittance by approximately 80%. And at about 420nm, it reduces transmittance by approximately 20%. This is important because transmittance at different wavelengths can have varying effects.

Examining Overall Blue-Light Reduction Claims

As previously noted, some companies claim a specific percentage of overall blue light reduction for their products. This is disingenuous because transmittance varies by wavelength.  

​For instance, the shortest wavelengths of blue light have the greatest impact on visual performance, that is, they are the most myopically defocused in front of the retina causing the greatest amount of chromatic aberration. If a particular lens transmittance is 60% at 400nm while another lens is 18%, clearly the lens transmitting 18% at 400nm will have a greater capacity to relieve digital eye strain.   

Throughout this series we have looked at how short arms (proximity), as well as pupil size and crystalline lens clarity (retinal illumination) make children more vulnerable to the effects of blue light from handheld digital devices. In closing with this section on lenses, it’s important to emphasize that eye care providers are fully informed on the exact benefit of the products being dispensed. Insist on transmittance curves for the lenses you prescribe to reduce blue light exposure.  

Learn even more about blue light and blue-light-reducing lens products. Download your free white paper, The Evolving Science of Blue Light.

About the author: Dr. Gary Morgan has been in private practice for 25 years in Arizona, with an emphasis on the care of patients at risk of, or with AMD. An advocate for innovation, he serves in a technical advisory capacity to ophthalmic industry enterprises focusing on spectacle lenses, nutraceuticals, and telemedicine that are intent on lessening the effects of AMD and blue light.