Science
Light is a biological signal.
Your body reads light as a clock.
This page is the long version: the cells, the evening, and what each NAKD lens is designed for.
01
A small group of cells in the retina keeps time. They are called intrinsically photosensitive retinal ganglion cells, and the pigment in them is melanopsin. They send a time signal to the brain.
02
Published action spectra place the peak sensitivity of these cells in the blue band, around 460–480 nm. That sits inside the band NAKD measures as blue light, 380–500 nm.
Berson, Dunn and Takao, Science, 2002. Brainard and colleagues, The Journal of Neuroscience, 2001. Lucas and colleagues, Trends in Neurosciences, 2014. Links are in the research chapter.
01
Melatonin is a hormone the body releases in the evening. Research has found that light can suppress that release, and that blue light does so more strongly than longer wavelengths.
02
Harvard Health Publishing describes the same pattern, and notes that red light is less likely to shift the clock. The sentence we print is the one cleared for NAKD, and it belongs with the Night lens only.
“Harvard Health recommends red light for evening use.”
NAKD Night is designed for the last 1–2 hours before bed. It is not a treatment, and it is not a promise of sleep.
Brainard and colleagues, 2001. Thapan, Arendt and Skene, The Journal of Physiology, 2001. Chang and colleagues, PNAS, 2015. Harvard Health, “Blue light has a dark side.”
Each lens is designed for one part of the day. The figures below come from lab testing.
Night · Deep red
Designed for the last hours before bed.
The deep red Night lens blocks 99.9% of blue light (380–500nm). Lab-tested. UV400 (~100% UVA/UVB). It is for IONA Night, KENT, MUSE and ROME.
Day Pro · Yellow
Designed for long screen days.
The yellow Day Pro lens blocks 98.5% of blue light. Lab-tested. UV400. That figure is VICE and IONA Day Pro Yellow only.
Day Amber · Clarity-first
Designed for daytime screens.
IONA Day Amber blocks 54% of blue light (380–500nm). Lab-tested. UV400. Daytime screens only.
SYNC · Orange
A clip-on for prescription frames.
SYNC is an orange clip-on that fits over most prescription frames.
Negative ions are found in abundance in nature, near oceans, rivers, waterfalls and forests. There's some early research linking negative ions to mood, but we want to be straight with you: there isn't enough research to say they do anything specific in eyewear, and we don't make any claims about it.
Our IONA range has minerals infused into the frames, which release negative ions. We've worn them ourselves and we love them. Because of how the minerals are infused, IONA only comes in black. It's our signature range. Our other styles, KENT, MUSE, ROME and VICE, come in different colours with the same lab-tested lenses, without the negative ions.
Day lenses are for screens. The Night lens is for the last 1–2 hours before bed.
Daytime
Day lens
Screens and indoor light.
Evening
Sunset. Lights and screens stay on.
Last 1–2 hours before bed
Night lens
For your last 1–2 hours before bed.
Evening use only. Not for daytime or driving. Day lenses are not for driving.
Sasseville studied blue-blocking glasses in bright light. Burkhart tried amber lenses in the evening. Neither paper tested NAKD.
A small set of cells in the eye sends a light signal that sets the body clock.
Berson DM, Dunn FA, Takao M. Science. 2002.
Read paper: Phototransduction by retinal ganglion cells that set the circadian clock. (opens in a new tab)How we measure light for the body clock has to include melanopsin, not just rods and cones.
Lucas RJ, Peirson SN, Berson DM, Brown TM, et al. Trends in Neurosciences. 2014.
Read paper: Measuring and using light in the melanopsin age. (opens in a new tab)Blue light is the strongest at suppressing melatonin in the evening.
Brainard GC, Hanifin JP, Greeson JM, Byrne B, et al. The Journal of Neuroscience. 2001.
Read paper: Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. (opens in a new tab)A second study found the same thing: short-wavelength light suppresses melatonin.
Thapan K, Arendt J, Skene DJ. The Journal of Physiology. 2001.
Read paper: An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans. (opens in a new tab)Harvard Health notes blue light at night can affect sleep.
Harvard Health Publishing. Harvard Health. Reviewed 2024.
Read paper: Blue light has a dark side. (opens in a new tab)Reading on a light-emitting screen in the evening delayed sleep and made people less alert the next morning.
Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Proceedings of the National Academy of Sciences. 2015.
Read paper: Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. (opens in a new tab)In this study, blue-blocking glasses reduced the effect of bright light on melatonin. The study did not test NAKD.
Sasseville A, Paquet N, Sévigny J, Hébert M. Journal of Pineal Research. 2006.
Read paper: Blue blocker glasses impede the capacity of bright light to suppress melatonin production. (opens in a new tab)A small trial used amber lenses in the evening and looked at sleep. It did not test NAKD lenses.
Burkhart K, Phelps JR. Chronobiology International. 2009.
Read paper: Amber lenses to block blue light and improve sleep: a randomized trial. (opens in a new tab)
A spectrophotometer measures what each lens lets through.
NAKD Night
99.9% blue light blocked (380–500nm) · UV400
Night lens, deep red
99.9%
blue light blocked (380–500nm). UV400.
Day Pro lens, yellow
98.5%
blue light blocked. UV400.
IONA Day Amber
54%
blue light blocked (380–500nm). UV400.
ANSI Z80.3 · EN ISO 12312-1 · AS/NZS 1067
SYNC is not part of this result.
- Night is for the last 1–2 hours before bed, and not for driving.
- Day lenses are for screens, and not for night driving.
Questions, answered.
Why are NAKD lenses tinted?
Clear lenses let most blue light through. To block 99.9% of blue light (380–500nm) in the evening, the lens has to be deep red.
Why do NAKD glasses cost more than cheap blue blockers?
Our lenses are lab-tested, block 99.9% (Night) or 98.5% (Day Pro) of blue light, carry UV400, sit in TR90 frames and come with 30-day returns on unused glasses. You buy once. No subscription.
Do I need both lenses?
Not to start. Most people start with Night and add Day if they spend long days at a screen.
Are NAKD glasses a medical device?
No. NAKD glasses filter light. They don’t diagnose, treat or cure any condition. If you have a sleep or eye condition, speak to your doctor or optometrist.
Can I wear Night lenses while driving?
No. Never wear Night lenses in daylight or for driving.