You have probably heard that blue light disrupts sleep. You may have already done something about it: bought a pair of amber glasses, turned on Night Shift on your phone, or made a habit of dimming your screens after sunset. That is a meaningful step, and the science behind it is solid. Blue light is the primary driver of melatonin suppression in the evening hours.
But here is what most people haven't heard: the cells in your eye that regulate melatonin don't stop responding to light at the edge of the blue spectrum. Their sensitivity extends into the green range. Which means if you've blocked blue light well but left green light unaddressed, you've handled the main problem without finishing the job.
This post explains how the melatonin suppression pathway actually works, why green light is part of the picture, and what that means for the lenses you wear in the hours before sleep.
How Your Brain Reads Light at Night
To understand why green light matters, you first need to understand how light suppresses melatonin in the first place.
Melatonin is produced by the pineal gland and its release is tightly regulated by your circadian rhythm, the internal 24-hour biological clock governed by the suprachiasmatic nucleus (SCN) in the hypothalamus. The SCN doesn't run autonomously. It takes its primary cue from light, specifically from specialised photoreceptor cells in your retina called intrinsically photosensitive retinal ganglion cells, or ipRGCs.
ipRGCs are different from the rod and cone cells that handle vision. Their job is not to help you see. Their job is to detect ambient light levels and signal the brain about the time of day. They do this via a photopigment called melanopsin, which has peak sensitivity at approximately 480nm, well within the blue light range.
When ipRGCs detect light, they send signals through the retinohypothalamic tract directly to the SCN, which then suppresses melatonin production in the pineal gland. The stronger and more sustained the light signal, the longer melatonin is delayed.
Blue light, at the 460-490nm range, activates this pathway most efficiently. Research published in the Journal of Clinical Endocrinology and Metabolism demonstrated that exposure to blue-enriched light in the evening can suppress melatonin by up to 53% compared to dim light conditions, and shift the circadian clock by up to three hours. This is why the conversation about sleep and artificial light has centred on blue light, and rightly so.
But melanopsin sensitivity doesn't end at 500nm.
Why Green Light Is Part of the Equation
The melanopsin photopigment that gives ipRGCs their sensitivity has a response curve that peaks at around 480nm but extends well into the green spectrum, from approximately 500nm to 600nm. The sensitivity is lower in this range than at the blue peak, but it is not zero.
Research from Harvard Medical School's Division of Sleep Medicine confirmed that green light also suppresses melatonin through the same ipRGC pathway. A study published in PNAS found that green light pulses could suppress melatonin and shift circadian rhythms, though with less potency per unit than blue light at peak wavelengths.
What this means practically: if you eliminate blue light from your evening environment but leave green light unfiltered, your ipRGCs are still receiving a signal. It is a quieter signal than blue, but it is present, and in the hours when melatonin onset is beginning, any unfiltered stimulation of this pathway delays the process.
This is not a new problem that requires a new solution. It is an incomplete application of an existing one. Most people addressing evening light exposure are blocking blue well and leaving green partially or fully open. The result is a meaningful improvement, but not the full biological outcome they are working toward.
What Different Lenses Actually Block
To understand the gap, it helps to look at what different lens types actually filter across the spectrum.
Clear lenses: limited blue, no green
Clear-lens blue light glasses are the most common variety on the market. They are typically marketed for eye strain relief and screen comfort. Most block somewhere between 10% and 30% of blue light, depending on the coating.
At that level of blocking, the effect on melatonin is minimal. The ipRGC pathway requires a meaningful reduction in blue light to measurably affect melatonin suppression. Clear lenses reduce glare and may ease visual fatigue, but they are not doing the biological work needed for sleep support. And they offer no filtering of the green spectrum.
If you own a pair of clear blue light glasses and expected them to improve your sleep, this is likely why the results were underwhelming.
Amber lenses: strong on blue, partial on green
Amber lenses are a genuine step up. A quality amber lens blocks 90% or more of blue light, which is enough to materially reduce ipRGC stimulation in the blue range. This is where real sleep benefits begin, and many people notice an improvement in how quickly they wind down after switching to amber in the evening.
The limitation of amber lenses is in the green spectrum. Most amber lenses block between 80% and 89% of green light, which means 11-20% of the green range is still getting through. When you measure amber lens performance against the full melatonin-suppression range (460nm to 600nm), they cover the blue peak well but taper off as the wavelengths move into the green zone.
The practical result: amber gives you the main benefit, the blue light reduction that directly addresses the strongest melatonin signal. But a residual green light signal is still reaching your ipRGCs in the hours before sleep, continuing to activate the pathway at lower intensity.
For many people, amber is a genuinely useful tool. If you use screens until 9pm and sleep by 11pm, amber lenses offer real protection. But for anyone who wants the most complete biological protection, especially those using screens late or who have existing difficulty falling asleep, that remaining green gap is worth addressing.
Red lenses: blue and green, addressed together
A red lens with full-spectrum evening blocking eliminates the green gap. Balterra's Night+ lens blocks 99.9% of blue light and filters over 97% of melatonin-suppressing green wavelengths up to 600nm. That coverage is verified by independent spectrometer data, not a marketing estimate.
At 97% green blocking to 600nm, the light signal reaching your ipRGCs in the evening is as close to biological darkness as you can achieve while still wearing glasses and using a screen. The melatonin suppression pathway loses both its primary and secondary inputs. Your body can begin the hormonal shift toward sleep on its natural schedule, rather than waiting for your environment to dim enough on its own.
The Spectrum, Made Practical
Here is a way to think about the three lens tiers in terms of melatonin biology:
Clear lenses: Block a small portion of the blue range. ipRGC stimulation remains high. Melatonin onset is largely unaffected. Useful for eye comfort. Not a sleep tool.
Amber lenses (Night): Block approximately 95% of blue light. ipRGC stimulation is substantially reduced in the blue range. Melatonin onset begins to recover. A meaningful improvement, especially compared to no protection. Green light continues to stimulate the pathway at reduced intensity, with 11-20% of the green spectrum still transmitting depending on the lens.
Red lenses (Night+): Block 99.9% of blue and 97% of melatonin-suppressing green wavelengths to 600nm. The ipRGC pathway receives its lowest possible signal from artificial sources. Melatonin onset is protected as fully as possible in a screen-present environment. Spectrometer verified.
The progression is not about one lens being "better" in a generic sense. It is about the degree of melatonin pathway protection that matches your actual evening habits and biological needs.
Which Lens Is Right for You
The answer depends on when you stop using screens, the nature of your sleep challenges, and how seriously you want to address circadian protection.
Night (amber) is the right lens if:
- You finish using screens at least two hours before bed
- You sleep reasonably well but want to support a more consistent wind-down
- You want a warmer-tinted option that is comfortable for extended evening wear
- You are new to circadian eyewear and want to start with a meaningful but less visually intense option
Night+ (red) is the right lens if:
- You use screens in the hour or two directly before sleep
- You have difficulty falling asleep or feel mentally alert at bedtime despite being tired
- You want the most complete melatonin protection currently available
- You already wear amber glasses and have not seen the sleep improvement you expected
For people who want to address both daytime cortisol rhythm and evening melatonin preservation, Balterra's complete circadian protocol pairs the Daytime yellow lens (worn at screens during the day) with Night+ (worn in the 1-2 hours before bed). Each lens addresses a different phase of the biological day. Together they cover the full circadian arc.
What "Spectrometer Verified" Actually Means
Blocking percentages in the eyewear industry are not uniformly measured or disclosed. Many brands publish marketing figures without accompanying data. Spectrometer verification means the lens has been tested by an independent laboratory using equipment that measures actual light transmittance across the wavelength spectrum. The number is not an estimate or a rounding-up exercise. It is a measurement.
Balterra's 99.9% blue light blocking and 97% green light blocking up to 600nm for Night+ are spectrometer-verified figures. When Balterra states that Night+ covers the melatonin suppression range to 600nm, that claim is backed by the data, not derived from it.
This matters because the difference between 80% and 97% green light blocking sounds abstract until you consider that the remaining 3% represents the residual signal still reaching your ipRGCs in the hours when melatonin is trying to rise. Specificity in blocking percentages is not a marketing detail. It is a biological one.
The Bigger Picture
Most people who have tried to address evening light exposure have started with blue light. That is the right starting point. Blue light is the dominant suppressor, and handling it well produces a real biological result.
Green light is not a separate problem. It is the remaining fraction of the same problem. ipRGCs respond to light across a range, not just a single point. A lens that addresses 99.9% of blue and 97% of green to 600nm is not doing something different from an amber lens. It is doing the same thing more completely.
Your melatonin system doesn't distinguish between the blue light coming from your phone and the green light coming from your television. It reads both. It responds to both. And in the two hours before you want to be asleep, what you want is for both signals to be as quiet as possible.
That is what Night+ is built to do.
Frequently Asked Questions
Does green light actually suppress melatonin?
Yes. The ipRGC cells in your retina contain a photopigment called melanopsin, which has peak sensitivity at around 480nm (blue light) but maintains sensitivity through the green spectrum to approximately 600nm. Research confirms that green light activates the same melatonin suppression pathway as blue light, though with lower potency per unit. Blue light remains the primary suppressor.
Do amber blue light glasses block green light?
Most amber lenses block the majority of blue light (90-95%) but transmit a portion of the green spectrum, typically 11-20% of green light passes through. This means amber lenses do not fully close the melatonin suppression pathway. They reduce the dominant blue signal meaningfully, but a residual green signal remains.
What wavelength range suppresses melatonin?
The melatonin suppression range spans approximately 460nm to 600nm. The peak is around 480nm in the blue range. Sensitivity decreases but remains biologically relevant through the green spectrum to approximately 600nm. This is why Balterra's Night+ lens is designed to filter to 600nm, covering the full range rather than stopping at the blue-only cutoff of most evening lenses.
When should I wear Night+ glasses?
Night+ is designed for the 1-2 hours before your intended sleep time. This is the window when melatonin onset is beginning naturally, and when unfiltered blue and green light has the most significant impact on delaying that process. Wearing Night+ consistently in this window gives your body the best conditions to begin the hormonal shift toward sleep on schedule.
What is the difference between Night and Night+ from Balterra?
Night is Balterra's amber lens. It blocks approximately 95% of blue light and is designed for use from sundown onward. It provides strong melatonin support with a less intense visual experience. Night+ is the red lens, blocking 99.9% of blue and 97% of melatonin-suppressing green wavelengths to 600nm. It provides the most complete circadian protection and is designed for the 1-2 hours directly before sleep, or for anyone who uses screens late and wants maximum biological coverage. Both are spectrometer verified.
All blocking percentages cited for Balterra lenses are independently spectrometer verified. Scientific claims in this post reference peer-reviewed research. Balterra products are not medical devices and are not intended to diagnose, treat, or cure any condition.