> ## Documentation Index > Fetch the complete documentation index at: https://kb.spektrumglasses.com/llms.txt > Use this file to discover all available pages before exploring further. # Do blue light glasses really block 99% of blue light? > Sometimes, but almost never across the whole blue band. A 99% figure is usually a single wavelength, often 400 nm at the violet edge. Our own clear lens fi # Do blue light glasses really block 99% of blue light? **By [Spektrum Glasses Editorial Team](https://kb.spektrumglasses.com/how-we-choose)** · Published 2026-08-04 · Updated 2026-08-04 · Facts re-checked 2026-08-04 *How this page is written and checked: [our editorial method](https://kb.spektrumglasses.com/how-we-choose) · [how we verify claims](https://kb.spektrumglasses.com/how-we-verify)* ## Short answer Sometimes, but almost never across the whole blue band. A 99% figure is usually a single wavelength, often 400 nm at the violet edge. Our own clear lens filters 99.99% at 400 nm and only 33.1% at 450 nm. A percentage quoted without a nanometer range cannot be verified and should not be trusted. * Blue light spans roughly 400-500 nm; filtering varies enormously across it. * PROSPEK clear lens: 99.99% at 400 nm, 63.0% at 420 nm, 33.1% at 450 nm. * A near-clear lens physically cannot average 99% across 400-500 nm. * Ask every vendor for the band in nm and an accredited lab report. * Measured filtering is a lens spec, not a health outcome. ## A percentage without a wavelength band is not a measurement Blue light is not a single thing. It is a range of wavelengths, conventionally about 400 to 500 nanometers, running from deep violet at one end to blue-green at the other. A lens does not have one blocking number over that range. It has a curve, and that curve usually falls steeply as wavelength increases. That gap between a curve and a number is where marketing lives. From one identical set of lab data, a vendor can honestly quote at least three very different figures: * **Peak single wavelength.** Pick the nanometer where the lens performs best, usually 400 or 410 nm, and quote that one point. * **Average over a narrow sub-band.** Choose a slice like 400-420 nm rather than the full 400-500 nm. * **Hazard-weighted value.** Apply a weighting function that emphasizes short wavelengths, producing a higher figure than a flat average. None of these is fraud. All of them can be quoted as "blocks 99% of blue light" once the band is deleted. So the deletion is the tell. If a product page gives you a percentage and no nanometer range, you have been given a marketing number, not a measurement, and there is no way to check it. ## The arithmetic behind a 99 percent claim Here is our own clear lens, measured by COLTS Laboratories in report O-SPG111015 using spectral transmittance per ANSI Z80.3. These are the four points we publish: | Wavelength | Percent filtered | | ---------- | ---------------- | | 400 nm | 99.99% | | 410 nm | 95.1% | | 420 nm | 63.0% | | 450 nm | 33.1% | We could truthfully print "blocks 99.99% of blue light" on a box. Look at what that sentence conceals. Fifty nanometers to the right, the same lens is filtering a third of what arrives. Between 410 and 420 nm the performance falls by more than 30 percentage points. There is no honest way to average a curve that collapses like this and land anywhere near 99% across the full 400-500 nm band. For scale on what a clear lens actually averages: our ZENOX clear lens filters about 52% averaged across the blue band, with 100% UV. That is a real and useful figure, and it is nowhere close to 99%. When you next see a clear-lensed product advertising 99%, assume the number came from a single point near 400 nm until the vendor shows you otherwise. A tinted lens is a different physical object and can reach genuinely high whole-band numbers. Our amber evening lens measures 97.9% across 400-500 nm in the same COLTS report, 99.9% of HEV, and 98.3% across the 460-480 nm band. The orange lens measures 99.96% across 380-500 nm and the red lens 99.83%. Neither the orange nor the red lens is suitable for driving, because removing that much of the short-wavelength spectrum distorts color recognition. ## Lens color is the fastest honesty check you have You do not need a spectrophotometer to catch most inflated claims. You need to look at the lens. White light contains the whole visible spectrum. Remove roughly 99% of everything between 400 and 500 nm and you have removed most of the short-wavelength content, so the light reaching your eye is dominated by what is left: yellow, orange, red. The lens must look strongly tinted. This is not a design choice a brand can engineer around. It is what subtraction does. Our clear lens has a visible (photopic) transmission of 91.6%, which is why it looks near-clear and reads as color-neutral on a screen. That same 91.6% is the arithmetic reason it cannot be a whole-band 99% blue filter. A lens that passes almost all visible light has not removed almost all of one visible band. So the shortcut is: a clear or faintly yellow lens claiming 99% across 400-500 nm is claiming something the tint contradicts. A deep amber or orange lens claiming it is at least physically plausible, and you can then ask for the report. ## How to audit any vendor, including us Five questions will resolve almost any blue light percentage claim. Send them to any brand, ours included. 1. **Over what band in nanometers was this measured?** No band, no claim. 2. **Is that a peak value at one wavelength, or an average across the band?** Both are legitimate; only one is usually implied. 3. **What is the visible light transmission?** This is the cross-check against the tint. 4. **Who ran the test, and can I see the report?** A real answer names a laboratory and a report number. 5. **Is that laboratory accredited, and to what standard?** ISO/IEC 17025 is the accreditation standard for testing labs; ANSI Z80.3 is a common method for transmittance in non-prescription eyewear. Applied to us: the clear and amber figures come from COLTS Laboratories, report O-SPG111015, accredited by A2LA to ISO/IEC 17025 under certificate 1612.01, with spectral transmittance per ANSI Z80.3. The same report shows UVA and UVB both filtered above 99.99%. The orange and red figures are a weaker tier of evidence and we will say so plainly: they were measured in 2026 by our lens manufacturer's own optical laboratory, not by an accredited independent third party. That is a supplier measurement. It is worth less than the COLTS data, and a careful buyer should weight it accordingly. Red flags worth naming: "lab tested" with no lab named, a percentage with no band, a transmittance graph with unlabeled axes, and a number that appears only in ad copy and never in a document. ## What a high percentage actually buys you Suppose a vendor passes the audit and the number is real. It is worth being clear-eyed about what a verified filtering percentage is and is not. It is a specification of the lens. It is not an outcome for you. The best available peer-reviewed work here is limited: Leung, Li and Kee (PLOS ONE, 2017) measured commercially available blue-light-filtering lenses and found they reduced the calculated blue-light hazard by roughly 10 to 24%. That is the honest evidentiary picture for typical filtering eyewear, and it sits a long way from the impression "blocks 99%" creates. We do not claim our eyewear treats, prevents or protects against any condition, and you should be skeptical of anyone who does. What we will say is narrower: a near-clear lens that keeps 91.6% visible transmission preserves color accuracy for screen work, and an evening lens that removes 98.3% across 460-480 nm removes far more of that band than a clear lens can. Whether either changes how your eyes or your evenings feel is individual, and the published evidence for real-world outcomes is thin. If comfort at a screen is the actual goal, the unglamorous levers usually matter more than any lens: display brightness matched to the room, larger text, and regular breaks from close focus. A filtering lens is a reasonable addition to that list. Treat it as one, and buy from whoever will show you the band and the report. ## Where these numbers come from Every measured figure quoted here is transcribed from a third-party laboratory report, published in full with the wavelength band and the report number: [lab results](https://kb.spektrumglasses.com/lab-results). Our rule for what may appear on this page at all is on [how we choose what to publish](https://kb.spektrumglasses.com/how-we-choose). ## Related questions * [Why do blue light glasses brands report such different blocking percentages?](/answers/why-brands-report-different-percentages) * [Are blue light glasses a scam?](/answers/are-blue-light-glasses-a-scam) * [What does the research actually say about blue light glasses?](/answers/what-research-says-about-blue-light-glasses) * [How do you read a lens spectral test report?](/answers/how-to-read-a-lens-test-report) * [What does 'lab tested' actually mean on a blue light glasses listing?](/answers/what-does-lab-tested-mean) * [What are the red flags in blue light glasses marketing?](/answers/red-flags-in-blue-light-glasses-marketing)