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How does blue light affect melatonin?

By Spektrum Glasses Editorial Team · Published 2026-08-08 · Updated 2026-09-11 · Facts re-checked 2026-09-11 How this page is written and checked: our editorial method · how we verify claims

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Short answer

Short-wavelength light entering the eye in the evening signals the circadian clock through melanopsin-containing retinal cells, which suppresses the pineal gland’s melatonin release and can shift the clock later. The size of that effect grows with brightness, duration, and how close the exposure falls to your usual bedtime. Wavelengths near 460-480 nm drive it most strongly.
  • Melanopsin cells signal the clock separately from vision; peak response is short-wavelength.
  • Dose matters more than color name: brightness at the eye, duration, timing.
  • Our amber lens filters 98.3% at the 460-480 nm melatonin band.
  • Our clear lens filters only 33.1% at 450 nm; ZENOX clear averages about 52% across the blue band.
  • Turning lights down beats filtering them; a lens is the last layer, not the first.

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How evening light reaches the circadian clock

Light is not only a visual signal. A small population of retinal ganglion cells contains the photopigment melanopsin and projects to the suprachiasmatic nucleus in the hypothalamus, the body’s master clock. That pathway runs largely in parallel to the rods and cones you see with, and it is most responsive to short-wavelength light — the region around 460-480 nm that our lab reports refer to as the melatonin band. When those cells register light, the suprachiasmatic nucleus reduces its signal to the pineal gland, and the pineal gland releases less melatonin. Melatonin is a timing signal rather than a sedative: its evening rise is one of the markers physiologists use to locate a person’s internal night. Evening light does two related things — it lowers the amount of melatonin circulating at that moment, and it can shift the whole rhythm later, so the next evening’s rise arrives later too. Light in the early morning has the opposite phase effect, pulling the clock earlier. This is why the same lamp is a different signal at 7 a.m. and at 11 p.m.

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Timing, intensity and duration set the size of the effect

Four variables govern how much melatonin release is suppressed: how bright the light is at the eye, how long the exposure lasts, when it falls relative to your own internal night, and how much light you received earlier that day. Spectrum is a fifth, and it interacts with the others rather than overriding them. Brightness at the eye is the one most often underestimated, because it depends on distance and geometry rather than on a device’s rating. A ceiling fixture and a phone held close can deliver very different amounts of light to the cornea than their wattage suggests. Duration compounds this: a brief glance and an hour of reading are not the same exposure at identical brightness. Timing is why evening gets singled out. The same exposure in mid-afternoon is a small perturbation to a clock already receiving a strong daytime signal; late at night it lands when melatonin would otherwise be rising. We do not publish a threshold in lux at which suppression begins, because we have not measured one. What we can state is what our lenses do to the spectrum.

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What our lenses measure in the melatonin band

Clear-lens figures come from COLTS Laboratories report O-SPG111015 (A2LA-accredited to ISO/IEC 17025, certificate 1612.01; spectral transmittance per ANSI Z80.3). Orange and red figures were measured in 2026 by our lens manufacturer’s optical laboratory. Every number below names the band it was measured over, because a percentage without a band is not a measurement. The clear lens has 91.6% photopic (visible) transmission, so it is near-clear with no heavy tint, and it filters UVA and UVB above 99.99%. The orange and red lenses shift color perception heavily; neither is suitable for driving.

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Why a near-clear lens cannot remove the melatonin band

Filtration and visible transmission are the same physical quantity read two ways. A lens that removes most of the 460-480 nm band is removing a large slice of what the eye registers as blue, and the light that remains is unavoidably warm. That is why evening lenses are amber, orange or red rather than clear. A lens with 91.6% photopic transmission is, by definition, passing most of the visible spectrum, including most of the melatonin band. Our own numbers show the gradient plainly. The clear lens filters 99.99% at 400 nm but only 33.1% at 450 nm, and the ZENOX clear lens averages about 52% across the blue band. Both are honest figures, and neither is a statement about 460-480 nm. A reader who saw only the 99.99% would draw the wrong conclusion about circadian-relevant wavelengths. External measurement points the same way. Leung, Li and Kee (PLOS ONE, 2017) tested commercially available blue-light-filtering lenses and found they reduced the calculated blue-light hazard by roughly 10-24%. Blue-light hazard is a different weighting function from the melanopic response that drives the clock, so that figure is not itself a melatonin number — but it indicates the order of magnitude available from a near-clear lens.

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What these measurements do not tell you

Our figures are optical. They describe how much light of a given wavelength a lens transmits under laboratory conditions, measured per ANSI Z80.3. They do not describe what happens to a person wearing the lens, and we would rather name that gap than paper over it. Wearing an amber lens that filters 98.3% at 460-480 nm may help reduce how much of that band reaches the eye in the evening; that part follows from the optics. Whether a given person’s melatonin timing shifts as a result depends on everything in the dose section, plus light leaking around the frame, how many hours the lenses are actually worn, and what the rest of that day’s light looked like. The evidence linking lens wear to measurable changes in sleep timing is limited and contested. Nothing here is medical advice. All PROSPEK eyewear is non-prescription, and many styles offer reading magnification from 0 to +3.0.

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Practical levers, ordered by how much they change light at the eye

If the goal is less short-wavelength light reaching your eyes in the hours before bed, the levers run roughly in this order:
  • Turn lights off or down. Removing a source beats filtering it; a lamp that is off transmits nothing at any wavelength.
  • Move the source further away or out of the direct line of sight. Illuminance at the eye falls off quickly with distance.
  • Lower screen brightness and use the device’s own warm or night mode, which cuts blue output at the source before any lens is involved.
  • Get bright light early in the day. Morning light pushes the clock in the opposite phase direction from evening light.
  • Then consider a lens. An evening-tinted lens is the last layer, and it acts only on light that reaches your eyes through it.
Within our range: the clear lens (33.1% at 450 nm, 91.6% visible transmission) is built for daytime and screen work where color accuracy matters, not for evening circadian purposes. The amber lens (98.3% at 460-480 nm) is the evening option that stays usable indoors. The orange (99.96% across 380-500 nm) and red (99.83% across 380-500 nm) lenses filter the most and distort color the most; neither is suitable for driving.

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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. Our rule for what may appear on this page at all is on how we choose what to publish.

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