How to test blue light blocking glasses at home

How to test blue light blocking glasses at home

If you want to know whether your blue light glasses are really safeguarding your health, you’re in the right place.

Science continues to the harm caused by chronic exposure to blue light and companies are taking note. Since the pandemic, we’ve noticed a stark increase in the options of blue light blocking products on the market.

With this, if you are looking to protect your health, it is worth checking whether the product you pick does what it says on the box.

In this article, we’ll discuss three methods that are commonly used to determine whether your glasses are up to spec:

  1. Spectral Transmittance Graphs
  2. The Colour Wheel Test
  3. The Blue Light Pen Test

Before we begin, it’s worth noting that normal prescription glasses are not designed to block blue light. Prescriptive eyewear is designed to correct eye problems and enhance vision, not to filter colour from the visible spectrum. To screen blue light from your field of view requires special lenses.

The Most Accurate Way to Test Blue Light Products is by using a spectrometer


A spectrometer is a lab instrument that splits a light source into wavelengths. Our products are then placed in the device; and the spectrometer measures which wavelengths are blocked by our products. You can read these results on a spectral transmittance graph.

Ocushield has three spectral transmittance graphs. One for our smartphone and tablet screen protectors. Another for the laptop, monitor and PC filters. The third is for our blue light blocking glasses. These reveal how much blue light our products block; it’s slightly different for each product.


The blue light that is most harmful to the eyes, both short-term (eye strain and headaches) and long-term (eye diseases such as macular degeneration) is found between 370-455nm. This is the range that a filter should, therefore, focus on blocking.

Our glasses filter out up to 99% of the wavelengths below 400 nm, and up to 40% of harmful blue light between 401 - 460 nm. They protect against the most dangerous rays while permitting a comfortable, usable screen.

If a product’s spectral transmittance graph reveals less than 30% of up to 455 nm blue light is blocked, leave them in the shop. They do not provide the level of protection you need and are a waste of your money

RGB Colour wheel test

This test sounds logical, but doesn’t work


This test states that, assuming you are not colour blind and there is no filter currently on your digital screen, the colours on the colour wheel will look true to life. When you place your blue light blocking glasses on and look again, you will notice the B section changes from blue towards black. This, in theory, indicates blue light is being stopped, just as the glasses are meant to do.

If the colour remains sharp and vibrant, if the blue remains distinctly blue, the wavelengths emitted from the screen are thought to remain unfiltered. In this case, the misconception assumes that the constancy of the image means a product’s claims do no match the end result: They do not block blue light.

However, while sounding logical, not all blue light is created equal. The longest and safer wavelengths of blue light that fall between 470-500 nm will still show. As such, blue light will be present - because we're not stopping all blue - just the bad stuff!

When blue light is removed entirely, the appearance of a digital screen changes markedly. This can make it difficult to view. If your glasses are not fit for purpose — if they do not limit the most harmful rays while being user friendly — they will sit on your desk unused. There, they offer no protection.

The blue light pen test

Don’t waste your time with this gimmick

A lot of cheap brands include a laser pen to prove that their anti-blue light products work. These tests claim that the pen emits blue light and the white card reacts to blue light by turning blue. Therefore, when you place your glasses or screen protector between the light and the card, the white card shouldn’t turn blue as all the blue light is blocked.

Majority of these cheap, mass-manufactured laser pens do not emit blue light - they don’t even come close to the harmful wavelengths of blue light. Their wavelengths are generally lower, emitting violet light not blue light. This explains the purple tinge on the card.

The jury is out. The only way to accurately assess the power of a blue light filter is an official spectrometer report from a lab that provides a third-party result.

No other manual test or gimmicky blue light card test can do the job.

Why choose Ocushield for your blue light blocking glasses?

At Ocushield, we understand that purchasing a pair of blue light blocking glasses is an important step. We also know that there are a range of possible options available and the decision may be difficult, even confusing. That’s one of the important reasons why we share our spectral transmittance graphs freely on our site. You can view them here.

Additionally, our products have been developed, designed, and tested by leading Optometrists in the UK. Our blue light filter is registered with the medical body MHRA, which is a world leading regulatory body. We have the expertise and experience, the technology and the training that ensures our glasses work.

The use of blue light blocking technology in our modern, digital age is a crucial, protective step. Spectral transmittance graphs ensure you receive products that protect your health, now and into the future.

How we reviewed this article:

Ocushield has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations.

Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.

Current Version
June 06, 2024

Written By

Dhruvin Patel | BSc Hons, MCOptom, Optometrist

Edited By

Omba Kumwenda | BA, MEng

Medically Reviewed By

Asad Hamir | BSc Hons, Optometrist

Copy Edited By

Tara Tadlock | MA

1 comment

  • Venomlily16

    Thanks for letting us know . I recently got a pair of blue light computer glasses as a birthday present and after using them, I couldn’t tell if they were helping or not . I figured maybe this was like a modern-day “Emperor’s New Clothes” concept where we were ALL being fooled into buying stylish, but useless glasses . I can’t believe I almost fell for the primary color circles thing .

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