Online, there are a lot glasses claiming to block, filter or reduce blue light. Without clear criteria for comparison, it is difficult to assess the effectiveness of a pair. This brief article focuses on two tools to assess blue blocking glasses, both before and after the purchase. 

Before You Buy Blue Light Filter Glasses 

The first step is to identify why you want to filter blue light. If your primary purpose is simply reduce the glare on the computer screen then a free software like f.lux may do the trick.   

If you are looking to truly filter out blue light - then be sure to search for the transmittance spectrum of the glasses you're considering. The transmittance spectrum is a graph that that illustrates the percent of light passing through the lens and most retailers should make them available if requested. For example, refer to the image below. 

 

The Y-axis shows the percentage of light that passes through the filter. The X-axis shows the components of wavelengths that are filtered or pass through. In this example, ~99% of light with wavelengths shorter than 520 nm are prevented from passing through the glasses. This lens shown in this graph effectively filters all violet, blue and a portion of the green spectrum. This graph is the transmission spectrum for our blue blocking glasses.

Test Your Blue Light Blocking Glasses 

Following a purchase, how can you test whether the glasses truly block blue light? One method is by comparing the two colour spectra shown below. 

(Original image from wikimedia Image released to public domain, however link to this article for use). Check out our other blue light filter test or learn about different types of blue blockers. 

If you have normal colour perception and your monitor can display RGB, the two colour spectra shown above should appear different. The upper spectrum represents a normal colour range. For the lower spectrum, a photo editing software was used to remove the blue hues. As you can see, the cyan component of the spectrum (which is a mix between blue and green) appears green. The blue component has disappeared. 

True blue blocking glasses, or lens that filter out >90% blue light, the two spectra should appear very similar. This should occur because the glasses should do mechanically what we've done using the photo editing software : i.e. filter out blue light.

Do you have a pair of blue filtering glasses that you tested out? Did the spectra appear the same? Let us know! Email : info@blueblockglasses.com or leave a comment below.