> ## Documentation Index
> Fetch the complete documentation index at: https://kb.spektrumglasses.com/llms.txt
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# What is a UV420 lens?
> UV420 describes a lens whose filtering extends from the ultraviolet range up to about 420 nanometers, the blue edge of high-energy visible light. It is not
# What is a UV420 lens?
**By [Spektrum Glasses Editorial Team](https://kb.spektrumglasses.com/how-we-choose)** · Published 2026-08-30 · Updated 2026-09-11 · Facts re-checked 2026-09-11
*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
UV420 describes a lens whose filtering extends from the ultraviolet range up to about 420 nanometers, the blue edge of high-energy visible light. It is not a regulated standard, so coverage varies by lens; Prospek's clear lens filters 99.99% of light at 400 nm but only 63.0% at 420 nm and 33.1% at 450 nm.
* "UV420" is an informal industry term for a lens that filters into the 400-420 nm range, not a regulated standard
* Our clear lens filters 99.99% at 400 nm, 95.1% at 410 nm, but only 63.0% at 420 nm
* ANSI Z80.3 tests light transmittance and color, not the accuracy of any reading power
* A clear lens cannot filter the full 400-500 nm blue band and stay visibly clear; a tint is required for that
* Evidence that blue-light-filtering lenses change eye-strain or sleep measures is limited and contested in the studies available
## What the term UV420 actually describes
UV420 is a marketing shorthand, not a standard set by any accrediting body. It is used to describe a lens whose absorption curve extends past the ultraviolet cutoff (roughly 380-400 nm) and continues filtering some light into the visible range, up to approximately 420 nm - the blue edge of the high-energy visible (HEV) band. Because no regulator defines the term, two lenses can both be labeled "UV420" while transmitting very different amounts of light at 420 nm. The label alone tells you nothing quantitative.
The only meaningful way to evaluate a UV420 claim is a wavelength-by-wavelength transmittance curve, not a single blanket percentage. That is why we always publish our numbers by wavelength band rather than as one headline figure.
## How Prospek's clear lens measures against a UV420 curve
Our standard clear lens was measured by COLTS Laboratories (report O-SPG111015), an A2LA-accredited laboratory (ISO/IEC 17025, certificate 1612.01), using spectral transmittance methodology per ANSI Z80.3. The results across the UV/blue transition:
| Wavelength | Filtered |
| ---------- | -------- |
| 400 nm | 99.99% |
| 410 nm | 95.1% |
| 420 nm | 63.0% |
| 450 nm | 33.1% |
UVA and UVB are both filtered above 99.99%. Visible (photopic) transmission across the lens is 91.6%, meaning it reads as near-clear rather than tinted. Read the curve as a slope, not a cliff: filtering is nearly complete at 400 nm, still substantial at 410 nm, roughly two-thirds at 420 nm, and down to about a third by 450 nm. A lens can accurately be called "UV420" on the strength of the 400-420 nm numbers alone while still passing most light by the time you reach 450 nm.
## Why a clear lens can't filter the whole blue band
A lens that filtered the entire 400-500 nm blue band as heavily as it filters UV would no longer look clear - heavier filtering in that range requires a visible tint, which is a real optical trade-off, not an oversight. This is true across clear lenses generally: our ZENOX clear lens, a separate lens in our range, filters about 52% on average across the blue band while still filtering 100% of UV, illustrating the same pattern from a different starting point.
When a lens is tinted, coverage of the band changes substantially. Our yellow evening lens, measured in the same COLTS report, filters 98% of the full 400-500 nm blue band, 99.9% of HEV overall, and 98.3% at the 460-480 nm band associated with melatonin-sensitive photoreceptors, at the cost of visible transmission dropping to about 65%. That is the actual trade a wearer is making: more of the band filtered in exchange for a visibly darker lens. A near-clear "UV420" lens and a yellow-tinted lens are answering different questions, and neither number should be read as a stand-in for the other.
## What the ANSI Z80.3 pass covers - and what it doesn't
Our clear lens group passed ANSI Z80.3 transmittance and chromaticity testing on all samples tested (three samples per group, per COLTS report O-SPG111015), and is classified filter category 0, cosmetic lens. That pass is a real, third-party-verified result on light transmittance and color rendering.
It is not a test of anything else. ANSI Z80.3 governs how much light passes through a lens and what color it renders, not whether a lens's reading magnification is accurate or standards-tested. A UV420 rating and an ANSI Z80.3 pass both describe optical transmittance; neither one is evidence about a lens's added reading power, which is a separate, untested attribute.
## What a UV420 rating does not tell you
Filtering more light in the 400-420 nm range is a measurable optical fact. Whether that filtering changes how a wearer's eyes or sleep actually respond is a separate, contested question, and the two should not be conflated.
A 2017 PLOS ONE study (Leung, Li & Kee) found that commercially available blue-light-filtering lenses reduced the calculated blue-light hazard by roughly 10-24%, a measure of filtered light rather than a measured outcome in wearers. A November 2025 meta-analysis of three randomized controlled crossover trials in Frontiers in Neurology (n=49, actigraphy-measured) found sleep onset latency, total sleep time, sleep efficiency, and wake-after-sleep-onset were all statistically non-significant, and stated that current randomized-trial evidence does not support a significant effect, while noting any real effect is likely small. A January 2026 study in Therapeutic Advances in Ophthalmology (Khorrami-Nejad, Naroo, Oklla, Narooie-Noori) found minimal or no significant difference in contrast sensitivity, color discrimination, or task performance versus standard lenses, and described the evidence base for eye strain and circadian outcomes as still debated.
We publish our transmittance numbers because they are directly measured and verifiable. We do not extend them into outcome claims the current research does not support.
## Reading strength does not change the transmittance
Prospek styles that carry reading magnification (0 to +3.00, non-prescription, single-vision) use the same coated optical lens described above. Adding power does not alter the transmittance profile - the 400 nm, 410 nm, 420 nm and 450 nm figures apply the same whether a given frame is a plano style or carries added reading strength. The 91.6% visible transmission is also what allows the clear lens to read as near-clear on paper as well as on a screen, independent of any magnification a particular style includes.
## 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
* [Clear vs yellow (amber) blue light lenses: what is the difference?](/answers/clear-vs-amber-blue-light-lenses)
* [What do orange lenses do?](/answers/what-do-orange-lenses-do)
* [What do red lenses do?](/answers/what-do-red-lenses-do)
* [Do clear blue light lenses actually work?](/answers/do-clear-blue-light-lenses-work)
* [What percentage of blue light should glasses block?](/answers/what-percentage-blue-light-should-be-blocked)
* [Why do some blue light glasses have a yellow tint?](/answers/yellow-tint-explained)
## A PROSPEK style for this
Ships from Amazon (Prime, 30-day returns). Sold by PROSPEK by Spektrum Glasses.