FL-41 THERAPEUTIC TINT
Rose-band notch filter
Sleepaxa Grandeur Umber Brown FL-41 Migraine Glasses
Acetate Rectangle, 23mm Bridge
Attenuates the blue and green wavelengths most often reported as migraine and photophobia triggers.
Size48-23-148
Front width142mm
Lens height40mm
FitMedium
ShapeRectangle
$119.00
$149.00
20% off
Free shipping to the US & EU · duties and taxes included · ships worldwide from our lab
Free shipping to the US & EU with duties and taxes included · delivered in 6–8 business days after dispatch.
One-year frame warranty · six-month lens warranty.
Cut, tinted and finished in the Sleepaxa optical laboratory.
30-day returns on zero-power glasses*
*Zero-power (non-prescription) glasses only, unworn and in original packaging. Prescription lenses are made to order and cannot be returned. Returns are shipped by the customer to our warehouse; return shipping is paid by the customer. Returns policy
Spectrometer lab reports
Third-party spectrophotometer readings for this exact lens. Every batch is verified before it ships.
Evidence
What sits behind this lens.
Every claim on this page traces back to a document you can open: a spectrophotometer report, a granted patent number on the public registry, or a peer-reviewed paper indexed by the US National Library of Medicine.
Spectrometer reports
Measured, not estimated
Third-party spectrophotometer readings for this exact lens formulation, tested to EN ISO 12312-1, ANSI Z80.3 and AS/NZS 1067.1. We publish the measured number either way, not only the flattering ones.
View measured lens data
Granted · Indian Patent Office
Two granted patents
Granted Patent IN 587746 for the dual-band NeuroCalm FLX+ lens and Granted Patent IN 597482 for Circadian560 — plus four more filings. Verifiable on the government registry.
See patent register
Peer-reviewed
PubMed-indexed research
Peer-reviewed research from our founder, published in Cureus and indexed on PubMed by the US National Library of Medicine (PMID 42524168).
Read the paperSpectral behaviour
Where this lens sits on the spectrum.
Wavelength bands and what the lens does across each one. Every batch is checked on a spectrophotometer before it ships.
Comparison
Why not just any blue-light coating?
Compare the mechanism before you choose. A coating reflects a little blue; a wavelength-selective lens absorbs a defined band and publishes the measurement.
| Sleepaxa lens | Typical blue-cut coating | Device night mode | |
|---|---|---|---|
| Blocks the melanopsin peak near 480 nm | Lab-verified | Partial, typically 10–40% | No |
| Covers the green band up to 550 nm | Red / Circadian560 lens | No | No |
| Spectrophotometer report you can open | Every batch | Rare | — |
| Granted patents | IN 587746 · IN 597482 | No | — |
| Peer-reviewed research on PubMed | Yes | No | No |
| Covers room light, not only the screen | Yes | Yes | No |
| UV protection | 100% UV400 | Varies | No |
Comparison based on our published spectrophotometer reports and on typical published specifications for generic blue-light filtering coatings and device night modes. No specific competing product is named or tested here.
Before you decide
Fit, tint and prescription.
The fitWill this frame fit me?
Look on the inside of the arm of a pair you already wear. You will find three numbers, usually printed as 52–18–145. They are, in order, the lens width, the bridge width and the arm length — all in millimetres. Match those to the frame below and the fit will be close.
| Lens width | Bridge | Arm length |
|---|---|---|
| 48-23-148 | 142mm | 40mm |
If your numbers are within about 2 mm of the frame, it will sit correctly. A narrower face suits a smaller lens width; a wider face suits a longer arm.
The lensAmber or Red — which one?
Amber is the all-day lens. Luminous transmittance around 50%, Filter Category 1, safe indoors and outdoors. It removes the blue band and part of the green band while leaving enough light through to read, cook and work. Wear it from late afternoon onwards.
Red is the night lens. Zero measured transmission from 380 to 560 nm, Filter Category 3, indoor use only. This is the one to put on two to three hours before bed, when the aim is to remove the circadian signal completely rather than reduce it.
Most people who use both wear Amber in the evening and switch to Red in the last hours before sleep. That is the reason the second-pair pairing exists.
The lensPrescription and lens index
Choose Prescription Lens and we cut the tint into a lens made to your power in our own lab. After checkout you will receive an email asking for your prescription and pupillary distance — you can also reply with a photograph of the prescription.
| Index | Suited to | Profile |
|---|---|---|
| 1.56 | Up to about ±2.00 D | Standard thickness |
| 1.61 | ±2.00 D to ±4.00 D | Thinner, lighter |
| 1.67 | ±4.00 D to ±6.00 D | Noticeably thinner edge |
| 1.74 | Above ±6.00 D | Thinnest available |
Not sure which index applies to you? Send us the prescription and our optometry team will select it for you at no extra cost.
Prescription lenses are made to order for your eyes and cannot be returned or exchanged, unless we made them incorrectly — in that case we remake them free of charge.
Everything elseShipping, returns, warranty and care
Free shipping to the US & EU with duties and taxes included · delivered in 6–8 business days after dispatch. One-year frame warranty · six-month lens warranty.
30-day returns on zero-power glasses* *Zero-power (non-prescription) glasses only, unworn and in original packaging. Prescription lenses are made to order and cannot be returned. Returns are shipped by the customer to our warehouse; return shipping is paid by the customer. Read the full returns policy.
Clean the lens with the supplied microfibre cloth only. Tinted lenses are absorptive through the full thickness of the material, so surface scratches do not change the transmission curve — but they do scatter light, which is worth avoiding.
Still deciding
Ask a clinician, not a chatbot.
Tint, prescription, lens index or frame fit — our optometry team answers directly.
Choose your second pair
The Heritage Series · FL-41
Grandeur Umber Brown
The widest bridge and the smallest eye in the range, cut from a solid block of acetate.
Grandeur is the extreme of one idea: a 48 mm eye, the smallest we make, carried on a 23 mm bridge, the widest. The lens sits far out from the nose and high on the face, so a small rectangle still delivers 40 mm of depth over the pupil. It is hand-cut from Italian cellulose acetate and polished across more than sixty separate steps, which is why the 142 mm front holds a crisp edge instead of a moulded one. Temples run 148 mm. For a narrow face that cannot tolerate bridge pressure, nothing else here comes close.
Two tints, two jobs
One small rectangle, two tint depths
FL-41 LightEveryday indoor filteringThe lighter of the two rose tints, drawn for all-day indoor wear. It cuts the same rose-band notch as FL-41 Dark but at a higher overall transmittance. The full spectrophotometer report for this tint is being finalized and will be published here. 100% UV protection (UV400).
FL-41 DarkBright rooms and glareThis is the darker of the two rose lenses. It reads 7.9% at 420 nm, 13.8% at 450 nm and 12.6% at 520 nm, then releases the long end, 44.2% at 570 nm and 100% above 670 nm. UV protection is complete at UV400.
All figures are single-lens spectrophotometer measurements from our own laboratory reports for this lens, tested to EN ISO 12312-1, ANSI Z80.3 and AS/NZS 1067.1. Individual response varies.
Fit
Will the Grandeur fit you?
Grandeur is medium overall at 142 mm but built around extremes: a 48 mm eye and a 23 mm bridge, the widest nose opening in the range. It suits a low or broad nose bridge and anyone who gets pressure marks from standard fittings. The 40 mm lens is deep relative to the small eye, so coverage is better than the outline implies. Temples are 148 mm, slightly long. A wide face will find the 48 mm eye too small.
| Frame size | 48-23-148 |
|---|---|
| Front width | 142mm |
| Lens height | 40mm |
| Fit | Medium |
| Shape | Rectangle |
| Collection | The Heritage Series |
| Material | Italian cellulose acetate |
| Lens options | FL-41 Light or Dark · zero power or prescription |
| UV protection | 100% UV400, both tints |
In the box
- Grandeur Umber Brown frame in your chosen FL-41 tint
- Hard case and microfiber cleaning cloth
- Spectrophotometer report reference for your lens
- One-year frame warranty, six-month lens warranty
Shipping. Free shipping to the United States and the European Union with import duties and taxes included — nothing to pay on delivery. Rest of the world: shipping is calculated at checkout and any local duties or taxes may be payable by the recipient. In-stock zero-power orders are processed within 1–2 business days and most orders arrive within 6–8 business days after dispatch. Every order ships from our own optical laboratory.
Prescription orders. If you selected a prescription lens, our optometry team emails you after checkout to confirm your power and pupillary distance. Lenses are not cut until that confirmation, so a prescription order takes 3–7 business days longer than a zero-power one.
Returns. Zero-power (non-prescription) glasses may be returned within 30 days of delivery, unworn and in the original case with the cloth and packaging. Prescription and custom lenses are made to order and cannot be returned or exchanged unless we made them incorrectly. Returns are shipped by the customer to our warehouse in Surat, India, and return shipping is paid by the customer. See our Returns policy for the full process.
Warranty. One-year frame warranty and a six-month lens warranty covering manufacturing defects. Accidental damage and normal wear are not covered.
Lens care. Clean only with the supplied microfibre cloth. Our tints are absorptive through the full thickness of the lens material, so surface scratches do not change the transmission curve — but they do scatter light, which is worth avoiding. Do not use paper tissue, alcohol wipes or household cleaners.
Standards. Every lens carries 100% UV protection (UV400) and is tested against EN ISO 12312-1, ANSI Z80.3 and AS/NZS 1067.1. Spectrophotometer reports for each lens family are published on our research page.
Questions. Write to connect@sleepaxa.com and our optometry team answers directly.