You can test blue light glasses at home, and you should. But the test that came in the box is not measuring what you think it is.
Here is the short version. The little blue LED pen most sellers include peaks at around 400 nanometres. That is violet light, sitting at the very edge of the visible range. Your monitor emits most of its blue at roughly 450 to 460 nanometres. So the pen proves your lens filters at 400nm, which is real and worth knowing, and it proves nothing about the light your screen actually makes.
We sell these glasses and we include that test too. We would rather explain what it shows than let you believe it proves more than it does.
The short answer
- Can you test at home? Yes, and three of the four tests below tell you something real.
- Can you get a percentage at home? No. That needs a spectrometer.
- Does the pen test mean nothing? No. It proves the coating is there and working at the violet end.
- Should a clear lens make a blue screen look black? No. If it did, the lens would be amber.
- The only real proof: a spectral report from the manufacturer.
The four home tests, and what each one really proves
1. The blue LED pen test
What you do: shine the pen at the card that came with it, then hold your lens in the beam. The card glows less through the lens.
What it proves: the lens filters light at around 400nm. The coating exists and it is doing something.
What it does not prove: anything about 450 to 460nm, which is where your screen puts most of its blue. It also gives you no number. "Less glow" is not a percentage.
Be careful with sellers who present this as proof of a filtering figure. It is not that.
2. The blue screen test
What you do: fill your screen with pure blue, then look at it through the lens.
What it proves: whether the lens is heavily tinted.
Here is the part that confuses people. Through an amber or yellow lens, that blue square goes dark and muddy. Through a clear lens, it stays blue.
That is not a clear lens failing the test. That is what clear means. A lens that turned a blue screen black would turn everything else yellow, which is why we do not sell one. More on that trade in gaming glasses: do they work, where colour accuracy matters most.
3. The reflection test
What you do: hold the lens under a bright white light and tilt it. Look at the light bouncing off the surface.
What it proves: our lenses throw back a faint blue or violet sheen. That reflection is the coating rejecting part of the spectrum. A plain uncoated lens reflects white.
This is the most honest of the quick checks, because you are seeing the coating do its job rather than reading a glow off a card. It still gives you no number.
4. The paper test
What you do: put the lens on a sheet of white paper in daylight.
What it proves: how much the lens shifts colour. A clear lens leaves the paper white. A filtering lens with a heavy tint leaves a visible yellow patch.
Use this one to check a seller's honesty. If a listing says "clear lens" and the paper turns yellow, the listing is wrong.
Why no home test gives you a percentage
Measuring how much light a lens blocks means measuring the strength of every wavelength that goes in, then measuring it again coming out, across the whole range. That is a spectrometer, and it is lab equipment.
Your eyes cannot do it. A phone camera cannot do it. A pen and a card certainly cannot.
So any number you see on a product page came from a lab, not from a test you can repeat. That leaves you with one useful question, which is the next section.
What "85 to 90 percent" actually means
This is the part almost nobody explains, and it changes how you read every listing you will ever see.
Blue light runs roughly 400 to 500 nanometres. That is a wide band, and lenses do not treat it evenly.
| Wavelength | What it is | Clear lens filters |
|---|---|---|
| 400 to 420 nm | Violet, highest energy | Most |
| 420 to 450 nm | Deep blue | Some |
| 450 to 500 nm | Blue into cyan, most of what a screen emits | Little |
A clear lens does its heaviest work at the violet end. That is exactly why it can filter strongly and still look clear: there is not much of your vision sitting at 400nm, so removing most of it barely changes what you see.
So when a seller says 85 to 90 percent, ask which band. Almost always it is the high energy end, not all blue light. A lens that removed 85 percent of everything from 400 to 500nm would be deeply amber, and you would know the moment you put it on.
Our figure comes from our supplier and covers the high energy band. It is not a claim that 85 percent of everything your monitor emits is stopped, and we are not going to let you read it that way.
The one thing worth asking any seller
Ask for the spectral report.
It is a chart showing how much light passes through the lens at each wavelength. It is the only document that actually answers the question, and a seller who has had their lenses tested will have one.
Most will not. That in itself tells you something.
Ask us the same thing. Email us and we will tell you exactly what we have and what we do not. If we cannot show you a chart, we will say so rather than point at a pen.
What to check before you buy
Forget the percentage for a second. These four things matter more and you can check all of them from a listing.
- Is the lens clear or tinted? If the listing will not say, assume amber. Clear keeps colours true, which matters for design work, video calls and games. Amber filters more and turns everything warm.
- Is there an anti-reflective coating? This is the part most people actually notice. It cuts reflections off the lens surface, and it is separate from the blue filter.
- Does it say non-prescription? If you can read your screen fine, you do not need a prescription. If the text is blurry, no filter fixes that. See computer glasses vs reading glasses.
- What does it cost? The filter itself is cheap to make. A $200 pair is a frame and a brand with the same coating on it. We break the market down in what blue light glasses cost in Canada.
One test that matters more than any of these
Wear them for a working week.
If your eyes feel easier by Friday, they earned their place. If nothing changed, send them back. You have 25 days with us, and we would rather take the return than have you keep something that did nothing.
And before you spend anything: turn your screen brightness down to match the room, move the monitor an arm's length away, and look at something across the room every twenty minutes. Those are free and they do more than any lens. Full list in our guide to digital eye strain and how to prevent it.
Where to start if you want a pair
Everything we carry is non-prescription and clear-lensed.
- Men's blue light glasses — wider frames, sizing guide included
- Women's blue light glasses — frame shapes by face shape
- Children's blue light glasses — read the eye exam note first
- Computer glasses — built for desk work and gaming
- Every pair we stock — if you would rather just browse
- Cases and cleaning cloths — a scratched coating filters less, so keep the cloth
Free shipping across Canada, 5 to 10 days, 25 day returns. New to all of this? Start with what blue light glasses are and whether they work, or see our blue light glasses Canada home page.
Common questions
How do I test blue light glasses at home?
Four quick checks: the LED pen test, the blue screen test, the reflection test and the paper test. Together they tell you whether a coating is present and whether the lens is tinted. None of them give you a filtering percentage, and only a spectrometer can.
Is the pen test that came with my glasses accurate?
It is real but narrow. Those pens peak at around 400nm, which is violet. Screens emit most of their blue around 450 to 460nm. So the pen shows filtering at one end of the range, not across it.
Do my blue light glasses work if a blue screen still looks blue?
Yes, if they are clear lenses. A clear lens is not supposed to black out a blue screen. Only a heavily amber lens does that, and it turns everything else yellow as a result.
How much blue light do glasses actually block?
It depends entirely on the wavelength. Clear lenses filter most strongly at the violet end, around 400 to 420nm, and far less at 450nm and above. A single headline percentage almost always refers to the high energy band, not the whole range.
How can I be sure before I buy?
Ask the seller for a spectral report. It is the only document that answers the question properly, and whether they have one is itself useful information.
Do scratches affect filtering?
The filter is built into the lens rather than sitting on top, so a scratch does not switch it off. But scratches scatter light and cause glare, which is the part most people actually notice. Use the cloth and keep the case.
About the author
Written by the team at Blue Light Glasses Canada, a Canadian store selling non-prescription blue light glasses since 2022. Our founder, Jesse Robert, has five years in eyewear retail.
We are not optometrists, and nothing here is medical advice. If your eyes hurt regularly, book an eye exam. We would rather lose a sale than have you skip one.
