How to Test Blue Light Glasses at Home (and Which Tests Are Useless)

Guide · 5 min read

You have bought a pair of blue light glasses and want to know if they do anything. Fair question. There are three quick checks you can do at home, one popular test that tells you almost nothing, and one piece of evidence that settles it properly.

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First, what you are testing for

Blue light covers wavelengths from roughly 400 to 500 nanometres. LED screens, including phones, laptops and TVs, put out a strong spike of blue at around 450nm. A blue light lens should reduce how much of that range reaches your eye. How much depends on the lens: clear lenses filter a modest slice, yellow and orange lenses filter a lot, red lenses filter nearly all of it.

No home test can give you a percentage. What they can do is tell you whether the lens is doing something or nothing.

Test 1: the reflection test (clear lenses)

Hold your glasses under a bright white light, or in front of a white screen, and tilt them until you see the light reflecting off the lens surface.

• Blue or purple reflection: the lens has a coating that reflects some blue light away. A good sign for a clear lens.
• Green reflection only: that is a standard anti-glare coating, which is not the same thing.
• No coloured reflection: a clear lens with no reflection is probably doing very little.

Tinted lenses work by absorbing blue light rather than reflecting it, so this test does not apply to them.

Test 2: the blue square test (tinted lenses)

Search for an RGB colour chart, or open any image with a pure blue block next to a black one, and view it at full screen brightness.

• Through an orange or red lens, the blue block should turn very dark or black, and be hard to tell apart from the black block. If blue still looks clearly blue, the tint is cosmetic.
• Through a yellow lens, blue should look noticeably darker and duller.
• Through a clear lens you will see little or no change. That is expected, and it is why this test cannot judge clear lenses.

Test 3: the white page test

Look at a plain white screen or sheet of paper through the lens, then without it. A clear blue light lens usually adds a very faint warm or yellowish cast. If white looks exactly the same, the lens is filtering very little. If the cast is strong, colours on your screen will be off, which matters for design or photo work.

The test to be sceptical of: the pen torch and card

Many glasses arrive with a small blue torch and a test card. You shine the light through the lens, the card does not react, and the glasses appear to block everything. The catch: most of these torches emit violet light at around 405nm, right at the edge of the blue range. Nearly any lens with a basic UV coating will block that. Your screen's blue peak sits around 450nm, which the torch does not test at all.

A pass on the pen test means very little. It is a demo, not a measurement.

What actually proves it: a transmission report

The only real measurement comes from a spectrophotometer, a lab instrument that records how much light passes through the lens at each wavelength. When you look at a report, check three things:

• The range covered. You want figures across 400 to 500nm, and especially around 450 to 455nm.
• What the headline percentage refers to. “Blocks 99% of blue light” may only be true at 400 to 410nm. Ask what the figure is at 450nm.
• Which lens was tested. A brand selling several tints should have a result for each one.

Any brand making a filtering claim should be able to show you this. If they cannot, treat the number as marketing.

Filtering is not the same as results

Proving a lens filters blue light is not the same as proving it will help you. The research on blue light glasses for eye strain and sleep is mixed, and we cover it in do blue light glasses actually work? A lens that passes every test above is a well made lens. Whether it makes your evenings more comfortable is something only wearing it will tell you, which is why a returns policy matters more than a test card.

How Clique lenses behave in these tests

Clique is one frame with a clear base lens and magnetic yellow, orange and red clip-ons.

If yours do not behave that way, tell us and send them back within 30 days.

Quick questions

Can I test blue light glasses with my phone?

Yes. Your phone screen is the blue light source for the blue square and white page tests.

Do darker lenses always block more blue light?

No. A grey sunglass lens dims everything equally. What matters is the colour of the tint: yellow, orange and red absorb blue specifically.

Why do my clear lenses fail the blue square test?

They have not failed. Clear lenses only filter a portion of blue light, too little to see by eye. Use the reflection and white page tests instead.

This article is for general information and isn't medical advice. Clique frames are lifestyle eyewear and not a medical device.