> ## Documentation Index
> Fetch the complete documentation index at: https://kb.spektrumglasses.com/llms.txt
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# How long before bed should you put on evening blue light glasses?
> Evidence supports putting on evening blue light glasses 2 to 3 hours before bedtime, when melatonin release typically begins rising and evening light most
# How long before bed should you put on evening blue light glasses?
**By [Spektrum Glasses Editorial Team](https://kb.spektrumglasses.com/how-we-choose)** · Published 2026-08-12 · 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
Evidence supports putting on evening blue light glasses 2 to 3 hours before bedtime, when melatonin release typically begins rising and evening light most affects the body clock. Our yellow lens filters 98.3% of light at 460-480 nm, but a 2025 meta-analysis of randomized crossover trials found no significant change in sleep onset latency, total sleep time, or sleep efficiency.
* Melatonin release typically begins rising 2-3 hours before habitual bedtime; light exposure in that window most affects the body clock.
* Our yellow evening lens filters 98.3% at 460-480 nm and 98% across 400-500 nm (COLTS report O-SPG111015).
* A clear lens filters only 33.1% at 450 nm despite blocking 99.99% at 400 nm - it is not built for evening use.
* A 2025 meta-analysis of 3 RCTs (n=49) found no significant effect of blue-blocking glasses on sleep onset, duration, or efficiency.
* A 2026 review calls circadian and sleep efficacy for blue-light lenses still debated; reducing overall evening light exposure is the better-supported step.
## Evening light and the timing of the body clock
Evening light exposure is the most solidly supported lever in this field for shifting the timing of the body's internal clock. Light reaching the eye in the hours before bed can delay the nightly rise in melatonin, the hormone associated with the onset of sleepiness. In people on a regular schedule, melatonin release typically begins climbing roughly 2 to 3 hours before habitual bedtime, and light exposure during that window has a larger measured effect on delaying the rise than light earlier in the evening or a few minutes of bright light right at lights-out.
That timing detail describes light exposure generally - overhead lighting, screens, any bright source - not any particular product. If the goal is to reduce blue light reaching the eyes during the window the body clock is most sensitive to, the practical answer is to put on evening glasses when you start winding down, generally 2 to 3 hours before your target bedtime, rather than waiting until just before turning off the lights. Wearing them for the last 10 minutes of a bright evening does little to offset the several hours of light exposure that preceded it.
## What the yellow evening lens filters, compared with clear
Our yellow evening lens and our clear lens are measured on the same spectral transmittance report - COLTS Laboratories report O-SPG111015 - and the numbers explain why we make two different lenses rather than one.
| Measurement | Clear lens | Yellow evening lens |
| ------------------------------- | --------------- | ------------------- |
| 400 nm | 99.99% filtered | - |
| 410 nm | 95.1% filtered | - |
| 420 nm | 63.0% filtered | - |
| 450 nm | 33.1% filtered | - |
| 400-500 nm band | - | 98% filtered |
| 460-480 nm band | - | 98.3% filtered |
| High-energy visible (HEV) | - | 99.9% filtered |
| Visible (photopic) transmission | 91.6% | about 65% |
The clear lens is built to look nearly invisible - it lets through 91.6% of visible light - and it filters UV and the far edge of the blue band almost completely. But its filtration falls off quickly moving into the middle of the blue band: only 33.1% at 450 nm. The yellow evening lens trades some of that visible-light transmission (down to about 65%) for much higher filtration spread across the 400-500 nm band (98%), including specifically the 460-480 nm band (98.3%), which our lab groups with melatonin-relevant light.
For comparison, a clear lens from a separate line we tested (ZENOX) averaged only about 52% filtration across the blue band despite blocking 100% of UV - a reminder that blocking UV and looking clear is not the same as filtering the middle of the blue band that evening-light research focuses on.
## How these numbers were measured
These figures come from COLTS Laboratories report O-SPG111015, produced by an A2LA-accredited lab (ISO/IEC 17025, certificate 1612.01) that measured spectral transmittance using the ANSI Z80.3 method. The clear lens group passed ANSI Z80.3's transmittance and chromaticity checks, filter category 0, cosmetic lens. That standard governs light transmittance and color only - it does not test or certify the accuracy of any reading power a frame may carry, and it is not a clinical or medical-device standard. We cite it here as evidence of how the filtration numbers were measured, not as certification of any effect on sleep.
## What the sleep research actually shows
Measuring how much light a lens filters is a separate question from whether wearing that lens changes how someone sleeps, and the second question has much weaker evidence behind it.
A November 2025 meta-analysis in Frontiers in Neurology pooled three randomized crossover trials (n=49) that measured sleep with wrist actigraphy. Sleep onset latency, total sleep time, sleep efficiency, and wake time after sleep onset were all statistically non-significant between blue-blocking and control lenses. The authors describe only a possible small effect and state that current randomized-trial evidence does not support a significant effect.
A January 2026 review in Therapeutic Advances in Ophthalmology reached a similar conclusion from a different angle: blue-light-filtering spectacle lenses showed minimal or no significant difference from standard lenses in contrast sensitivity, color discrimination, and task performance, and the authors describe efficacy for eye strain and circadian or sleep outcomes as still debated.
Neither paper is about our lenses specifically, and neither rules an effect in or out - both describe the current evidence as thin and inconsistent rather than settled in either direction.
## What we do and don't claim about timing
Given that evidence, our position on the yellow evening lens is narrow and tied to what we actually measured. It may help reduce the amount of light reaching the eye in the 460-480 nm band during the hours before bed - 98.3% filtered per the COLTS report - which lines up with the mechanism described above. It is not represented as a way to address insomnia or any diagnosed sleep disorder, and no medical claim is made for it.
The more established step, based on the research above, is reducing overall evening light exposure - dimming room lighting, lowering screen brightness, and keeping a consistent light-dark schedule in the hours before bed. Evening glasses layered on top of that habit are a 'may help' addition tied to the measured filtration figure, not a substitute for it, and not something we present as resolving sleep difficulties.
## 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
* [How does blue light affect melatonin?](/answers/blue-light-and-melatonin)
* [Do blue light glasses help you sleep?](/answers/do-blue-light-glasses-help-you-sleep)
* [How long before bed should you stop looking at screens?](/answers/what-time-to-stop-screens-before-bed)
* [How does blue light affect cortisol and the stress response?](/answers/blue-light-and-cortisol)
* [How does blue light affect your circadian rhythm?](/answers/blue-light-and-circadian-rhythm)
* [Yellow (amber) or clear lenses for evening screen use?](/answers/amber-vs-clear-for-sleep)
## A PROSPEK style for this
Ships from Amazon (Prime, 30-day returns). Sold by PROSPEK by Spektrum Glasses.